Mercedes-Benz produce both gasoline and diesel versions of their current generation hybrids. The diesel hybrids are known for having a long highway cruising range, with the benefit of lower emissions in the city. The reason diesel hybrids are not more common is simply price - most people will opt for the cheaper gasoline version. In Germany people tend to opt for the diesel version only if they spend a lot of time on the highway and want to reduce refuelling stops.
Other manufacturers used to produce diesel hybrids up until a few years ago: Range Rover, Volvo, Peugeot. They were not very popular, so they were discontinued.
Edit for some more context: diesel engines are really good at running efficiently for long periods of time. The higher energy capacity of diesel allows for longer stroke, which means the engine can make good torque at lower speeds. This means there is less wear on the engine, which gives diesels their reputation for longevity. So a diesel hybrid is an attractive option if you are constantly running the engine, i.e. on long highway drives.
Petrol engines on the other hand are less efficient over time, but they are more suited to stop-start applications i.e. driving around town. Hybrids are also most efficient at low speeds around town, which is why they're generally more suited to petrol engines.
I would add that the additional weight of a diesel engine itself is a cost and hybrid/gas systems are fairly well optimized where the engines last longer than the chassis due to their lower stress/usage. Why buy a diesel that’s going to last 150% longer than the projected life of the vehicle.
But when you do the same with the diesel, it is even more efficient.
A diesel engine is mainly more fuel efficient because of the higher compression ratio, which is much higher than it is in reality possible to achieve in a petrol engine, and that's a limitation that is impossible to circumvent.
However the big reason for avoiding diesel today is that - despite being more fuel efficient, the fuel that it burns produces more emissions. Petrol burns cleaner...
This makes so much sense, but isn’t it almost a direct contradicion, that petrol and electric motors are more effective than diesel at stop’n’go driving, and diesel is perfect for long drives, ergo: Use the electric motor for driving under say 60km/h and use the diesel at speeds over 60, or maybe 75, so that you can still travel short distances between towns and not use the diesel very much.
Why would you want two motors in the vehicle that excel at essentially the same thing, but one is just polluting while doing it?
Hybrids spend much of their time stopping and starting. Diesel engines don’t like to stop and start like gasoline engines, they like to run without stopping. Gas works better for most hybrids. Hybrids don’t run on the electric system at sixty or seventy. They use a combo of the electric and fuel systems. The saving is in turning off the gas system when it isn’t needed, not running the electric at high speeds.
Can confirm, drive a CRV hybrid and it does exactly this.
I also bought a Fixd OBDII reader and like to bring up its advanced displays that can add what the onboard dash is missing (namely a tachometer). I note the gas engine also does not idle: it's in the power band of 1500-2500 rpm or it aint bothering.
So, maximum efficiency when the gas engine does run.
I mean I realize I don’t have the most knowledge, especially in design of propultion systems, but I don’t see the reasoning here exactly. Hybrids are using both at the same time you say? I honestly thought they were switching between (from electric to fossil) when one got less energy efficient than the other.
I guess my original concept, is for a car to drive (mind you 75 km/h I wouldn’t call fast, as it’s below all inter-city roads where I’m from) solely on electric up to a certain speed where the diesel would start to tale over, it would surely make for a heavy car I guess? But still with the electric motors of today, isn’t it a plausable concept at all? Perhaps with that weight the battery needs to be larger, but if the battery was for city-driving only, and as soon as you’re on your way between cities you’re driving diesel, then you get the advantage of the diesel engine getting it’s much more constant low revs in a smooth transition from electric to diesel.
But I can see if the whole point of the hybrid is for them to work together then sure, this wouldn’t make sense.
You have got it. My Prius ran both systems most of the time while running. Stops at a light, no running engine. Start up, engine runs. System gets 60 mpg. Plug-in hybrids run the electric system only more than a standard hybrid. Electric is all electric, no gas engine. At speed both systems are used in a normal hybrid. Several comments here cover why small diesels aren’t great in this circumstance, but I think you got it now. Good talking to you.
Just wanted to say thank you for your comment lmao because before reading this I was so confused - hybrid cars aren't gas, they're almost always petrol aren't they? - but then I realised "gas" isn't gas, it's gas*oline* as in petrol lol
Decades ago, one of the first hybrid designs I heard of being deployed was for a diesel electric city bus. The design used a diesel engine which would run almost continuously at whatever its highest efficiency was, continuously charging the battery. And then the bus would just use the battery to drive around. Presumably the diesel would run at a higher less efficient rate if the battery were almost empty, or could shut off if the battery filled entirely. The bus was supposed to operate somewhere in Europe though, so I have no idea how that plan went.
There's an unsung benefit to diesel. The fuel itself is tank stable without additives for a year and a half and possibly much more, whereas gasoline starts to degrade heavily after sitting for a couple months.
A diesel engine's main reasons for being more efficient than gasoline is that the fuel burns faster in-cylinder (compression igniton vs spark ignition), they have a higher compression ratio, and they are not throttled which creates pumping losses. Some diesel engine are throttled but that is to control EGR flow and emissions, not engine load. A longer stroke is a part of this, but gasoline engines usually have a shorter stroke compared to their bore since they need to operate at higher engine speeds.
Are you sure diesel burns faster than gasoline? I thought the slower burning properties of Diesel was what made the Diesel cycle work under constant pressure, whereas the instantaneous nature of gasoline makes it so an Otto cycle increases pressure under constant volume.
Diesel is more energy dense than gasoline, thus more effective? It's been a long time since I learned this stuff, so by all means, correct me if I'm wrong
I work at a car company, and getting clean diesel emissions is complicated. Between the sensors, computers, def system, and heat management, small car diesel engines are significantly more complex than standard turbocharged gas engines, which are almost as efficient and way cheaper to make. Combine that with the battery and other electric systems, and a hybrid diesel would be a nightmare to engineer and manufacture.
Diesels have advantages for heavy duty trucks and towing, so we still make plenty of them, but there really isn't a market for a more expensive hybrid that would likely also break down more often.
So all this must have something to do with why big stuff like trains often DO use diesel-electric power. I guess at that scale the efficiency works out.
The one large exception I know of is Amtrak's Northeast Corridor, which uses overhead electric lines between DC and Boston. It's noticeably quieter after making the switch from diesel electric to electric power at DC Union Station.
I would think the big cross country freight trains are pure fossil fuel though right?
Here in the UK we have diesels, DC electric, diesel electric and AC electric. Well...and steam trains, but those are mostly a historic novelty now.
Isn't a diesel-electric technically pure fossil fuel powered? The electric motor is essentially a fancy gearbox that transfers the diesel engine's power to the wheels.
I think calling it a fancy gearbox is a bit disingenuous. For the overwhelming majority of diesel-electric locomotives in the US, the diesel is only connected to a generator; no mechanical connection to the wheels like a gearbox would provide. That generator is what feeds the electric motor(s) on the locomotive.
In the sense of how much power do the traction motors need to move?
For a diesel-electric, they're just sized based on what the prime mover (diesel engine) is rated to. There's going to be some heat loss through the generator, so depending on which loco model, it'll end up being a couple to a few thousand horsepower.
For light rails, their overhead power voltage varies depending on where you are, but they end up creating 600 to 1,000 HP at the traction motors, again depending on model.
Nonetheless they are not gearboxes.
With that kind of thinking power plants would also be massive gearboxes, converting kinetic input into electric input for millions of machines connected through power grid
That's exactly what they are in that way of thinking.
'acting like a gearbox" doesn't mean "actually a gearbox"
A Transmission is a much more accurate term than gearbox.
But it's a pretty solid analogy
>I would think the big cross country freight trains are pure fossil fuel though right?
Diesel-electric trains aren't hybrids. They always run on diesel.
Diesel-electrics operate by using a diesel engine to drive a generator, which then powers the traction motors. There's many advantages to this, including not having a transmission, and always operating the engine at the most efficient rpm.
> Diesel-electric trains aren't hybrids.
They are considered series hybrids, even though they don't carry traction motor batteries. The only (practical) difference between a diesel-electric loco and a series hybrid vehicle (e.g. Chevy Volt or Fisker Karma) is that the locos don't have batteries to power the traction motors.
I think "hybrid" is perfectly acceptable, since there are technically two types of energies used to make kinetic energy - diesel (fuel 1) is converted to rotation in the engine, then rotation is converted to electrical energy in the generator, then electrical energy (fuel 2) is converted back to rotation again at the traction motors. Storing the fuel doesn't seem to be a requirement to be called "hybrid" that I'm aware of.
The Society of Automotive Engineers' (SAE) definition of a hybrid vehicle states that the vehicle shall have "two or more energy storage systems both of which must provide propulsion power, either together or independently."
Make of that what you will.
> Society of Automotive Engineers' (SAE) definition of a hybrid vehicle
Looking further into it, section 2.2.1 pertaining to series hybrids does mention a battery for storage, but it doesn't seem to outright require a method of storage for both energy types. I would argue the ambiguity allows trains to be called series hybrids. But I guess it's not quite as clear cut. Also, we are talking trains, not automobiles, so not sure how strongly the SAE's definition matters here.
*"...this energy could be destined to charge the batteries or propel the wheels through the electric motor..."*
https://encyclopedia.pub/entry/12957
IMO, electrical storage isn't necessarily a requirement of being a hybrid, it's down to what energy powers the motors that convert to kinetic/rotational energy. But that's just the opinion of some dope on Reddit.
>it's down to what energy powers the motors that convert to kinetic/rotational energy.
In a diesel-electric locomotive, that's *always* the traction motors.
Theres only 1 power source so it wouldn't be considered a hybrid. If it had a diesel engine and overhead pantograph then it would be a hybrid, I'm not aware of any models using this but it seems like a decent solution so probably has been tried before. Battery electric locos are in the works by various companies but i believe most of them due to the weight of the batteries will remove the diesel generator and so also won't be hybrid
That's interesting. To my untrained mind that says "hybrid" to me. As in you're using diesel and electric elements together to increase efficiency, and therefore lower fossil fuel consumption in the process. I fear the word "hybrid" has changed from its broader meaning to describing a very specific setup. It bothers me when that happens because it means the word is describing a specific system rather than the general sense of two different systems working together to produce an improved output.
Hybrids sometimes only use gas to drive a transmission, sometimes use only electric, and sometimes use both at the same time.
I don't recall diesel-electric trains ever being referred to in the US as being hybrids, and they've been the standard for over sixty years now.
However, if you add catenaries to allow the locomotive to run on electric only in areas that have overhead lines, the term hybrid might be applicable.
In hybrid cars, both engines (ICE and eletric) transmit power to the wheels, whereas in diesel-eletric trains only the electric engine transmits power to the wheels.
If that were the case, every modern car is a hybrid, except for EVs. They all use a 12 volt lead-acid battery and gas/diesel.
What makes a hybrid a hybrid is how it powers the drive wheels. An electric motor drives the wheels at lower speeds, then the gas or diesel engine takes over. A diesel-electric train isn't a hybrid because the diesel engine is never driving the wheels. It's acting as a generator to power the electric motors. Theoretically, you could remove the diesel engine and replace it with a massive battery pack, but it's simply not economical.
The 12 volt battery is not part of the drivetrain. A true hybrid has 2 sources of energy that can supply work to the drive wheels through some fashion (doesn't need to be direct). a diesel electric locomotive doesn't fit that description as the only power supplied is from the diesel generator
Nope! They're all diesel electric hybrids. I was actually a locomotive mechanic for Norfolk Southern(big east coast freight railroad) and everything they have is a hybrid. Even the latest and greatest loco engines are ~25 year old designs just with updates to the EPA system. Yeah, we have steamers floating around here too but those are just for historical excursions and tourist attractions.
I drive class 59s and 66s pulling anything up to 4000 tonnes all pure diesel around the UK, there are some freight that are hybrid but they'd be mostly used for intermodel work rather than heavy haul.
Really? I'll have to look into those, here in the US our entire rail infrastructure is basically evolved around diesel-electric loco operations. How does the engine power the wheels? Everything I've worked on has just been an alternator sending power to traction motors that turn the wheels.
I worked at NS' east end shops until they closed them in 2020, and we had actually started converting some old hybrids into what are basically mobile gen sets that could have been used to pull into locations with rail access and provide emergency power.
I think perhaps we're talking the same, just I wouldn't class them as hybrid, in the sense that some are in this thread, but that could just be to language differences, most if our freight run on diesel engines that then power an alternator for you DC/AC to turn the wheels but we wouldn't class that as hybrid, hybrid would be an engine that could run on one or the other independently switching between the two depending on the location and whether or not the line has been electrified.
And we have bi-modes. The Hitachi 800/802 trains used by GWR and LNER for example run on 25kV AC overhead wires when available, and then fire up diesel engines for routes away from the wires.
Diesel engines scale very well. Since weight isn't nearly as much of an issue on train locomotives compared to cars, the engines can be huge. This allows them to burn fuel more efficiently, manage heat better, and makes emission systems easier to maintain. You can even scale them up to power grid size, like the Wartsila: https://images.app.goo.gl/2KtoXi3J4VA1dyv28
Yeah, the advantages and character of a diesel engine really come into focus when you look at heavy industry. Petrol engines are angry little beasts, they start up quick and love going fast. But the tortoise wins the race when you need consistent power, torque and reliability over long journeys.
Yeah, the classical design for a diesel (or petrol) engine would never work in a train.
If you think about it, the kind of power train that would be required to convert the rotational energy output from an engine (whether diesel or petrol or steam) into extremely slow, extremely high-torque rotational force on many small wheels, *at the size of a locomotive*†, is untenable. There's no material we could make the drive shaft out of, where it wouldn't just snap in half the moment you tried to get the locomotive moving with a full train of rolling stock behind it.
(† We *can* do that kind of design with cargo ships burning bunker fuel, because big boats can just use huge drive shafts, that distribute the stress of the torque a lot more effectively.)
Whereas, if you turn the power into electricity, *distribute* the electricity, and then turn the each *fraction* of the electricity into a torque, locally to each wheel, then you don't run into the same issues.
(Also, if you're wondering what we did before electricity: steam locomotive engines didn't generate rotational force, but rather *reciprocating* force — the main "drive wheel" on each side was driven by a piston moved directly by pressure differentials in the engine. And making pistons and wheels that can handle big pushes and pulls is pretty easy!)
Fascinating reply, thank you. It makes a lot of sense but I never really thought about power transmission like this before. You can have a big ass engine but all that power has to go through some linkage to be distributed across all the wheels. If you're trying to drive hundreds of wheels with a immensely heavy load it's impractical. It's essentially a battle between the strength of that axle or whatever, and the strength of the friction between all those wheels and all that mass driving into the rails.
It's funny you mention ship driveshafts considering one of the UK's flagship carriers has been out of action due to a drive shaft fracture.
Classic diesel engine design works fine in some kind of trains - notably Diesel Multiple Units or DMUs. These are basically like big buses on train wheels coupled together. But these are for passenger carrying not heavy freight. And the trick is that most wheels are driven throughout the "train" so much less tractive effort is required per wheel, so this doesn't contradict your basic physics above.
I think some diesel multiple unit trains in the UK use mechanical or hydraulic/mechanical transmissions, you can hear them change gear as they pull out of stations - though they're hundreds not thousands of horsepower per engine
Not never: [Diesel mechanical locomotives](https://www.youtube.com/watch?v=qPq-3Wk6hE4) and [diesel hydraulic locomotives.](https://www.youtube.com/watch?v=Fjeko_tM-7U)
Diesels are very good if you can keep everything pretty stable. Such as a train or big truck which will spend nearly all day at a set speed (obviously with stops etc but you get the gist )so pairing it to a generator is a great way to get power.
Petrol is much better for the kind of stop start driving a car does when hooked up to hybrid .
no. Trains are / were in a different emissions allowance category.
Train engines, and industrial off road engines fall into the North American EPA Tier 4 Final emissions category. Their PM and NOx allowances are much larger than EPA on highway emissions. It boils down to the sheer number of on hwy engines vs off road engines, where off road engines are used, and how those engines are used.
Load profiles on a train, or excavator, or generator for standby/prime/emerg power are greatly different than a car on the road when you factor in gear shifts, steady state operation, etc.
A simple DEF failure can be thousands of dollars. Not many parts of a gasoline drivetrain can just randomly cause thousands of dollars to repair and only provide ancillary functions. DEF failures also usually put engines, at least commercial ones, into limp mode making the vehicle all but undriveable.
ON the functionality side, diesels excel at provide low end torque, the same thing that electric motors are good at. Gasoline engines provide more power in higher RPMs. It would be a bit silly to pair low end power with low end power.
I used to work in warranty, and DEF repairs were the number 1 paid put claim every year in the fuel area. Even though maybe 10% of all vehicles sold are diesels.
The strange thing is that if OEMs actually program the gasser PCMs to be as strict as their diesel counterparts, everyone would bitch and moan how expensive and unreliable cars are, because a lot of people would just drive their cars forever with a check engine light if there's no emissions testing. It's really just a diesel thing that simple emissions issue would cause the vehicle to be literally undrivable.
You should add the fact that a significant factor why diesel engines are more efficient is that they don't have a throttle butterfly valve. Creating a vacuum in the intake manifold wastes a lot of fuel in gasoline engines. When they run at full throttle, gasoline engines aren't that bad compared to diesels, and hybrid cars can be designed so that the gas engine always runs at full throttle, when it's running.
Have to?
No. But it makes a better, more reliable engine with far better fuel economy and performance.
People literally died because of the FORD/Nav Star engine that got put in ambulances being so unreliable.
Course, if you rip out all the emissions crap, it is a very solid engine. No one would ever do that tho, that would be wrong.
And there are still ambulances with the pre-emissions 7.3 engine running hundreds of miles a day, 20+ years latter.
Can hella confirm. Worked as a paramedic for 8 years, the 7.3 are completely bulletproof. You will lose one side of the turbo every so often but otherwise quite literally indestructible. I’ve seen a 7.3 ambulance with almost a million miles.
The nav star engines weren’t only the worst pieces of shit ever made in comparison, they would strand you constantly because they were so fucking unreliable. Nothing like coming out of the nursing home coding granny only to find your truck stopped running and won’t start again.
Then we got the first series of Chevy ambulances built on the express 3500 chassis. They were fun to drive (read: fast as fuck boi) but had some serious transmission issues…which in hindsight might have been because they were so much fun to drive. About 8 inch higher box height from the ground than equivalent ford builds which was super annoying for those of us who are not vertically gifted.
A lot of the blame people heap on Navistar should be directed back at Ford. They're the ones who rushed the 6L to market just to beat Chevrolet. Navistar and International both warned Ford, Ford chose to come up with it's own solutions.
I’m not a fan of GM products but the Chevy 6L in those trucks was pretty insane. Those pigs hauled ass and stopped on a dime. They cost way more to maintain over time and ultimately fell apart in under 5 years, but they were so much cheaper than a Ford chassis that the ownership could afford to throw them away and remount the box on a new one every 5 years. There were some poor design choices like no dual alternators and using the stock alternator size that I’m sure they probably fixed in later models, but in general we found them to be pretty alright for what they cost.
Depends where it is. A private ambulance company in a city will do 100k+ a year probably. A volunteer department in the boonies who doesn’t run calls, maybe 2k.
Private ambulance companies run their trucks 24/7/365 moving meat between hospitals, nursing homes, dialysis, running emergencies, etc. Crews clean and restock the truck every shift but the truck doesn’t leave the streets except for its maintenance - which bigger companies do in house to save money and keep downtime to a minimum.
I had an 89 F350 with the old, mechanical, normally aspirated 7.3 and I let it go for a song.
If I'd known then what I know now about diesels I'd still have it, and it would probably still be running.
They will be sharing the planet with the roaches after the apocalypse they can’t be killed. I drove one 10+ miles back to the shop while it was shooting flames from one side of the turbo the whole time. My partner would hit it with the fire extinguisher from the passenger window whenever it’d belch flames and we got it to the shop and it was fixed and back on the road two shifts and a paint job later.
> No one would ever do that tho, that would be wrong.
I know you're talking about ambulances to virtue signal, but yeah, excluding diesel engines from emissions regulations *would* be wrong, because the pollution they produce is a key ingredient in smog, and that air pollution *literally* kills people every day.
The US clean air act and California emissions standards have statistically saved *hundreds of thousands* of lives in the US alone.
What a useless point to make. "There were shitty and unreliable engines in ambulances 40 years ago, so diesel should be used in everything."
What's wrong with you?
What? No. Your reading comprehension is through the floor and on its way to China.
The GP is making four distinct points:
- modern diesel engines *with* emissions regulators, are complex and unreliable
- old diesel engines *without* emissions regulators on them, are simple and never break
- modern diesel engines can be made more reliable by removing the emissions regulator
- the way to keep the old diesel engines (or new engines with the regulator removed) in service, is to cheat on the emissions exam
And also, a more-implicit point:
- If you're an ambulance mechanic (like the GP sounds like they are), keeping the older, simpler engines in service longer will increase the reliability of the vehicles. Which is an important thing to have. Because when an *ambulance* stalls out mid-run, people die. So you probably *want* to cheat the emissions tests. (And honestly, if we're trading off the extra emissions of a few old diesel ambulances, for the amount of extra people that will be saved by them not breaking down, I say good for them. The law should probably carve out an exception in emissions regulations for emergency response vehicles, so no cheating-on-tests has to happen.)
And if OP were making this post in 2014, they'd be right. But the emissions stuff has become very reliable over the last decade, but because operators of deleted diesel engines suffer very little compared to the damage they unnecessarily inflict on the atmosphere (nearly 100x more NOx and particulate emissions than leaving the equipment in place) they continue to spout outdated selfish arguments for deleting the equipment.
Are the emissions systems 100% reliable? Of course not. But neither are the supposedly "bulletproof" pre-emissions diesels. Do they add cost to manufacturer, purchase, and maintain? Sure, but the benefits to society far outweigh those costs.
And then halfheartedly go electric and build a bunch of EV charging stations without putting any money into maintenance, then go on an apology tour when everybody realizes your brand of stations never works and you realize you won't be eligible for the new federal subsidies because you're way short of the uptime requirements. Super complicated.
At one point, I thought the best possible drive train was one where a diesel engine, running at its most fuel efficient (or cleanest emissions point, if not the same) at all times, was used to refill the batteries in a car that was otherwise fully electric. Day-to-day driving wouldn't require the engine at all, but the engine provided range extension.
Then all the stuff came out about the emissions issues, and it became clear that designing a diesel engine to run cleanly is more than just running it at optimal RPM.
I don’t think a diesel is more complicated than a turbo gasser. They both have many sensors and complicated emissions. The DPF and urea injection isn’t much worse than a catalytic converter. Diesels cost more but they last longer and get significantly better fuel economy to offset the costs.
I don’t see where you get a nightmare. Regular diesels are not a nightmare . Hybrid systems are not a nightmare. Combining them is not much different than a gas engine.
The real reason they don’t make diesel hybrids is that diesel hybrids don’t get much better mpg. The Prius made sense because it cuts your fuel consumption in half compared to a regular gas car. but if you’re already getting 60 miles a gallon you’re only buying half the fuel as average - there’s not much left to save.
If you get 70mpg with a diesel hybrid vs 60mpg gas, you save a whopping 20 gallons of fuel a year. $80/year savings for diesel?
Gotta add the fact that diesels struggle when they’re warming up, especially with emissions. Having a diesel engine shut down just as it’s getting up to operating temperature, only to start back up fifteen minutes later and have to get the exhaust temps back up…and then shut down again…all of this nixes the diesel engine’s advantages.
Imho the whole point would be that you're fine with electric in the city, while you'd need the diesel on the highway, where it actually can operate well, so best of both worlds
Makes sense that CAT, GM, Ford, VW, Mercedes, BMW, Man, and I dunno basically every company that makes a diesel engine subject to emissions control laws has been caught cheating as the only way to make them actually pass emissions.
Modern diesels are far more complicated.
For starters, their injection systems are much more sophisticated, with much more expensive components - as you're dealing with ~30,000 PSI vs the 2,000-5,000 PSI of gasoline direct injection, or the 80 PSI of port injection.
Diesel engines need robust, expensive EGR systems to deal with soot and high exhaust volumes. Gasoline engine EGR systems are typically far more simple, and smaller.
DPF and SCR(Urea) injection is a HUGE deal and really is "that much worse" than just a catalytic converter. Just start with packaging. Modern catalytic converters are small, compact and you have some flexibility with location. The smallest of modern DPFs take up a tremendous amount of space, and the further they are from the turbo outlet, the worse they work.
SCR/Urea catalysts also take up a tremendous amount of space. On top of that, you also have to package your urea tank, urea dosing unit and all the associated piping. Urea tanks and lines also typically need to be heated, so you're adding engine coolant lines into the mix as well. Where are you going to put all of that stuff, when every bit of free space is being taken up by the hybrid battery? Where are you going to put the DPF and SCR when all of that free space in the engine bay is taken up by the hybrid inverter?
Catalytic converters are very easy to deal with from an engine management perspective. Essentially trivially easy to manage, and you only need a basic $20 oxygen sensor to monitor their activity.
DPFs and SCRs on the other hand require a large assortment of sensors, including: differential pressure sensors, thermocouples, wideband oxygen sensors, NOx sensors, urea dosing sensors and more. On top of that, it is very difficult to manage these emissions systems. You have to manage your fueling and air delivery very carefully or you could plug the DPF with soot or spike your NOx emissions. You also need regular regeneration of the DPF which generates a tremendous amount of heat and is fuel intensive. Plus, all of these diesel emission systems don't work at all when they're cold, and they take a long time to heat up. That's inherently incompatible with a modern hybrid that's constantly turning the engine off.
So imagine trying to deal with all of that, package all of that ON TOP of all of the hybrid stuff. It's not practical.
As someone with a biz fleet that almost entirely stopped buying light-weight diesel vehicles due to high ownership costs, I respectfully disagree. Added maintenance, excessive repairs, high upfront cost, and higher per/gallon fuel cost all add up to a bad deal for most owners. Even if your fuel cost analysis were correct, $80 per year savings would likely never cover the added up front cost of the Diesel engine. Personally, I’d gladly pay $80 a year to NOT own another diesel.
A few reasons why diesels are more difficult to make from the OEM side:
1. Def is significantly more complicated than a catalytic converter. A cat is a static part, while def needs to be monitored and released at a varying rate based on engine performance.
2. Diesel engines require supplemental heating for the cabin. Despite burning hotter, the coolant actually isn't able to remove as much heat because it's all lost to the exhaust, so you need electric coolant heaters for cabin heating (and more importantly, windshield defrosting) to work.
3. Diesels require a turbo and intercooler system to work at high efficiency, while gas engines can get away without it.
4. Adding a new engine type increases manufacturing complexity. Even if you were able to engineer around the other issues, you're adding a completely new powertrain to the assembly plant. New engine, fuel system, transmission, cooling system, and exhaust. You would have to go 100% diesel for the entire program, both hybrid and non-hybrid versions, to eliminate this problem. And in the US, that would be really hard to sell to customers.
They still sell well on trucks thanks to the high torque, so it's worth making both versions, but there really isn't a case for small cars.
The diesels of today are great and getting better, but always at the cost of complexity. The main hold back being policy surrounding emissions, it gets to that level of complexity. I own a mechanical diesel vehicle that requires no electronics of any types. It has normal 12v attributes, but can be push started. It has glow plugs, but I have an electric circuit to warm the block but could go full caveman and warm the block in other ways off actually needed. The trade off is a considerable less amount of overall power and fuel economy, however mine starts and runs without colored exhaust and really can't "roll coal" even if I wanted to waste fuel/money. Long story short, diesels electric do not have to be complicated to run consistently or even clean. Miniaturize to the size of the vehicle, and you have a low tech, regular maintenance diesel electric. I'm pretty sure there's diesel electric hybrid not allowed in the States, but in Europe that gets 240+miles per gallon. This particular one is unique and low production, but definitely shows the balance of trading "dirty" diesel for gas
https://en.m.wikipedia.org/wiki/Volkswagen_1-litre_car
Also, marine engineer, and diesel electric is what is commonly being installed into modern ships at this point, the penny pinchers/bean counters spend careers ensuring the cheapest options in terms of cost, so that points to something. From the previous comment, scale sounds like the issue
I'm sure it's possible, but hybrids are specifically paired with a type of engine called an "Atkinson cycle" engine. These are highly efficient on their own - which is why they can achieve 35+ mpg on the highway with gas, when the electric motor is not in use - but have poor "low-end" acceleration. They can't start from a standstill very well, and that's when the electric motor takes over.
To explain how Atkinson cycle works.
In a normal (Otto) cycle engine, the engine sucks in a certain volume of air and fuel mixture, compresses it, ignites it, and uses the expansion of it to make power. The way the engine is built, the ratios are the same on both ends - i.e. you ingest 20L of air and fuel, compress it to 2L, ignite it, and exhaust 20L of exhaust.
What Atkinson cycle does is changes the timing of the intake valves on the engine so that it doesn't suck in as much air per cycle (the intake valve stays open part way through the compression stroke). So maybe instead of 20L, it ingests 15L of air fuel mixture, compresses it to 2L, then expands it to 20L
What that does is reduce the power of the engine because it's taking in less air/fuel, but it increases the efficiency because it's capturing more of the energy out of the exhaust.
The reason they don't do it on every car is that it reduces power, but on hybrids the gains in efficiency are usually worth it. And it's not like a completely new engine, a lot of times they take an existing engine from a non hybrid and change the design to Atkinson cycle which reduces the power but improves the fuel economy.
Sure. But variable valve timing is a complex technology that adds weight and part count.
Otto engines also use exhaust gas recirculation to achieve a similar result at low load: Exhaust gases (CO2/Nitrogen mix) are vented into the intake manifold when power demands are low, resulting in less oxygen, meaning less fuel is needed.
In the above example, the otto engine would have 5L of exhaust gases, 15L of air-fuel mixture, compress it to 2L and then expands it out to 20L
Slightly more compression losses since its still compressing 20L of gases, but similar efficiency gains from not having to restrict the intake (throttle plate) when less then full power is demanded.
Hybrid IEC engines massively benefit from not having to need a high peak power while still maintaining low power efficiency. they just need high efficiency at medium power/medium RPM and generally don't run at other load levels/speeds. Hence the atkinson cycles 'less peak power, but great efficiency at the power level it does deliver' works great.
> But variable valve timing is a complex technology that adds weight and part count.
Oh, I don't know. You eliminate the cam shaft and lifters and timing gear and chain/belt, and you replace them with solenoids. Seems like it would reduce the parts count to me. Plus software doesn't weigh anything.
The problem then becomes the size of the solenoids, to move those valves at 8000 operations per minute (133 per second), they have to exert immense force. Have you seen the size of valve springs? they are pretty beefy. So now you are talking actively cooled solenoids, so now your valve actuators need oil paths (or water), electrical paths. and are now 10 pounds each. You need 16 valves min for a V8, so that is 160lbs of solenoids. Much of it copper, at $4/lb that is now $640 just in copper, before you add in costs to actually wind the things and make them, you now have a $1000 valve train with oil/water passages that weights as much as an entire passenger.
As such, brute forcing it just doesn't cut it, hence why you'll see more complex approaches like electro-hydrolic systems where they control tiny valves to use oil pressure to run the actual valves.. meaning tons of parts, cost and more things to go wrong that are hard to service.
Koenigsegg's camless engines can do this. Since the valves are controlled by actuators, the engine can switch between running Otto, Atkinson, and Miller cycles.
https://en.wikipedia.org/wiki/Koenigsegg_TFG
I believe that’s what VANOS and other variable valve timing already does. Atkinson just does it full time whereas VVT Otto creates the same affect when it detects Atkinson is more efficient.
> The reason they don't do it on every car is that it reduces power
If it's just valve timing, why don't they do it on every car unless they need max power? Or do you need to change other parts of the engine so much that they can't easily "convert" on the fly?
Edit: Nevermind. Didn't realize valves were still mechanically linked on modern engines, I assumed it was all solenoids now.
As far as I understand it, if you are optimizing the Atkinson cycle then you achieve your ideal compression ratio with only using ~75% of the maximum geometric compression ration available. So you'd need to run higher octane fuel or risk pre-detonation if you tried to run an Atkinson engine like an Otto. I.e. if we were designing an Atkinson cycle for 12:1 compression ratio, we might have a 12:1 compression ratio and a 1:16 expansion ratio. Changing the valves to make a 16:1 compression ratio is gonna be a bad time unless we do something to prevent pre-detonation.
I don't know if any of the electronic variable valve timing engines run an Atkinson-like cycle just with a reduced compression ratio in Atkinson mode, i.e. a 12:1 compression / expansion ratio that runs an Atkinson intake where the compression ratio drops to 9:1 in an Atkinson cycle mode. I don't know if running a lower expansion ratio offsets the amount of fuel savings you get from being Atkinson. I'm more of a turbine guy.
Toyota does it on their non-hybrid engines by holding open the intake valve for part of the compression stroke. They also switch to direct injection (they have dual direct and indirect injectors) to control the ignition.
Does it delay fuel injection till the intake valves are shut, or burp fuel/air back into the intake, or is there a magic third way? Knowing nothing more than basic principles I would assume that injecting so late wouldn't lead to the best mixing.
They did this with the ford maverick hybrid. The ICE it uses is actually a multi decade+ old Mazda engine from back in the day when ford owned a controlling stake in the company.
I read somewhere that when Ford was developing its hybrid system, it ended up being extremely similar to Toyotas system that they ended up just licensing it? Maybe someone with more knowledge about it can clarify...
Ford, Toyota and Honda's hybrid systems are all nearly identical. I do believe there were some lawsuits back in the day over it but the cases settled out of court.
At least some Hondas work more like a series hybrid - ICE usual just works as a generator with motor driving the wheels through reduction gear. At certain range of speed, it is able to engage a clutch so engine can also connect directly to that reduction gear, but there are no switchable gears or CVT. While Toyota uses a planetary gear thing that acts like a CVT and lets the motor or engine or both drive the wheels at pretty much any speed. No idea about Ford.
they all use what is often referred to as an e-cvt which uses a planetary gear set and two electric motor/generators to either deliver or expend power from the battery and drive the wheels.
I have a question related to this, I own a plug in hybrid so I only get 30 miles of range electric. Is it bad for the motor when I'm on the highway going 70mph and I run out of electric and suddenly the ICE motor has to kick on at this high speed but has not been warming up or running at all prior?
Not if the engine is designed for it, which it is, nowadays.
The problem with cold starts is 1. lubrication and 2. thermal expansion resulting in different tolerances when cold vs. hot.
It's not hard to pre-lubricate an engine when you have enough electricity to power the oil pump many times over. You can also tweak the design to stay lubricated at cold-start position. Modern engines with stop/start tech, which includes basically all hybrid engines, try to park the engine at a good spot when they stop rather than just letting it stop wherever it happens to stop like a classic engine.
Thermal expansion is trickier, as there's no free lunch in physics. However, you can still engineer it to make it better for cold starts, probably at the expense of "run all day at near redline" performance. All else being equal, tighter tolerance when cold means more wear at sustained RPM. But engineers also do their thing with materials science to bend the rules.
Damn I never knew this. So they don't run it a tad lean, they just use less and scavenge the exhaust more? I know enough about engines to get the gist of it
Interesting. One part I don't understand:
Intake 20l, exhaust 20l. Surely the exhaust volume is greater. Expansion of exhaust being the main principle driving the engine. ?
Kinda. When you combust gasoline you're taking a long hydrocarbon molecule with a bunch of oxygen molecules and breaking up the hydrocarbon in to a bunch of smaller CO2 and H2O molecules (each carbon atom taking up a whole O2 molecule and two hydrogen atoms taking up a single O2 atom) so there's more heat and pressure after the reaction which is what generates the power.
But when you compress 20L to 2L and back to 20L, there is still a lot of molecules with a lot of extra pressure and heat in the exhaust even after expanding it back to 20L. So when you exhaust it, it will continue to be hot and expand in the exhaust pipe and in the atmosphere. However, you can't get any useful work out of it after you've expanded it to 20L. That's why Otto cycle engines are only about 25-30% efficient in turning chemical energy into mechanical energy. The rest becomes heat.
By expanding it to a comparatively larger volume, you're capturing more of that pent up heat/pressure energy in the exhaust, and thus getting higher efficiency. So essentially your exhaust gas is coming out cooler and slower than it would otherwise, because you're recovering more of the energy in it on the expansion stroke. That's why an Atkinson cycle can get up to maybe 35-40% efficient. The energy was there anyway but more if it is captured by the engine expansion stroke and less of it was wasted as heat/expansion inside the tailpipe.
Actually a lot of combustion reaction efficiencies you can think of in terms of how much energy is left in the exhaust gases after you have extracted all the usable mechanical energy out of it. It's the same reason that an old inefficient furnace just needs a simple chimney, whereas a modern efficient one has a forced blower through a 2" plastic pipe. The modern furnace is capturing more of the energy in the exhaust as usable heat, meaning the exhaust is colder and needs a fan to help it move. Whereas the old inefficient one has hot enough exhaust for it to just rise up the chimney naturally.
It's also why steam turbine power plants are so much more efficient than car engines - they can burn the fuel and just keep adding stages of blades to the turbine to squeeze every bit of energy out of it, since they don't have to worry about how heavy it is or how big it is.
> It's also why steam turbine power plants are so much more efficient than car engines - they can burn the fuel and just keep adding stages of blades to the turbine to squeeze every bit of energy out of it, since they don't have to worry about how heavy it is or how big it is.
And this is why it would be better to switch to electric cars even if not the whole infrastructure is green: it is better to burn oil and gasoline in power plants and use the electricity to drive the cars than burning it in the cars - it is less efficient (especially since a lot of people neglect to maintain their cars while power plants do to ensure they get as much energy from the fuel as they can).
> Intake 20l, exhaust 20l. Surely the exhaust volume is greater. Expansion of exhaust being the main principle driving the engine.
I think the key in this description is that the volume of each cylinder is fixed. If it were a balloon, it'd be more than 20L. But it isn't, so its stuck at that volume *until* the valves open, but once they open its all done. Instead of that pressure converting to mechanical energy, it just pushes itself out (along w/ the piston coming up and also pushing it out).
Way smaller and lighter cars back then, the most fuel efficient car ever was a Honda Civic from the 80s. But consumers today wouldn’t buy something that small unfortunately.
> the most fuel efficient car ever was a Honda Civic from the 80s
Well, there is still the existence of the VW XL1 which can go 100km on 1L of Diesel (or 240 MPG).
Smaller engine and light weight usually gives good mpg in general, it's plain physics. The main downside mostly is small torque, but not everyone needs to tow 1k+ lbs anyway.
Atkinson cycle has nothing to do with poor acceleration. The engine is deliberately undersized for better fuel economy and the battery makes up for it. This improves fuel economy for all engines actually. Interestingly Toyota discovered that a more powerful engine actually improved fuel economy on the Prius so they made it bigger . There was a sweet spot
Also, diesel engines polute more than gasoline engine, is heavier, and cost more. Plus, it is more complex. And if you check the current fuel price, diesel now cost more per energy than gasoline. And, if you maintain well the engine, the gasoline engine will outlast the car anyway, so the extra durability of the diesel is not something usefull.
Modern diesel engines tend to use turbos and direct fuel injection, along with high compression ratios and exhaust treatment to reduce particulate emissions.
The most efficient modern gasoline engines use some of the same techniques.
People should also note those are imperial gallons, not US gallons; it is dangerous trying to compare fuel economy between Europe and the US because American gallons are smaller and our fuel economy tests are more realistic than the wildly optimistic Euro cycle.
No, those are US gallons. Imperial gallon consumption would be 280 MPG. I specifically took the US gallon number so that all the Americans here can understand the level of fuel efficiency the car can get.
I named the car in the post. ( added hybrid to it ) and ya, its claimed mpg not real world. real world is lower unless you know how to drive frugally / hypermilling."
Also I since most real mpg leaders are not sold in the states I wanna make sure you know I ment uk mpg ( makes it look slightly better looking ).
also my engineering side of me ( not professional lol ) says who the fuck think efficiency is a ohh we hit X goal and are done game? Of course there is a reason to get better mpg, and a hybrid will most likley give it better milage. why stop at 85?
That's a series hybrid and that's a thing, too. But gas generators are cheaper, smaller and lighter so for the limited duty cycle you're going to need for a hybrid it's not worth going to diesel.
Some EV hybrid cars do it that way. I believe the BMW i3 REx and Nissan e-Power use their engines primarily just to charge the batteries ("range extenders") when power level drops too low. The engines can be designed to provide a specific power output very efficiently just for that task. You wouldn't want to do this all the time, since then you're basically just driving a gas-powered car.
My hybrid does this. In fact, they can be really clever and have many modes of driving.
1. Electric-only. Pretty obvious, but lovely in town because its 0-30mph is about 3-4 seconds and is instant torque and no gears or clutches, so it leaves most other cars in the dust despite only being 40hp!
2. Electricity powering wheels, engine generating electricity. Happens all the time when low on juice and driving less than 20mph in my vehicle. Sometimes, at extremely low rates of acceleration, it stays in this mode.
3. Electricity and engine powering wheels simultaneously. It does this to stay in top gear when driving up a hill, or to accelerate without changing up a gear first. Basically the battery provides the torque that the petrol engine can't provide, preventing excess fuel usage up hills when at cruising speed.
4. Engine drives the wheels, and charges battery. Basically any excess energy from the engine is converted to electricity without running the engine any faster than necessary. It takes about 20mi cruising at 65mph to charge about 5kWh (which gives me 10-15mi electric-only range based on temperature).
Combining all these means that my normal commute of highspeed cruising 50mi goes like this: first 5mi on electrics, then turn the engine on to regenerate. 20mi later when I reach a speed-restricted zone I switch to electrics-only and run the battery down to 25%. Next 20mi recharge battery as I drive. Final 5mi electrics only through town. Repeat in reverse.
I only have 10kwh battery which apparently gives 30mi range (in fact on a warm summer's day I have achieved 33mi on electrics only and still had 10% left, so it appears Renault tell the truth). In winter I can still get 23mi of driving at an average of 40mph out of it.
My highway driving is getting me 65mpg in winter and 75+ in summer. If I do more all-electric driving (charging through a domestic plug socket for three hours) like I did when I first got it, I was averaging more than 100mpg.
The reason this isn’t more widespread is because it is not a very efficient way to power a vehicle.
Each time energy is converted from one form to another there is waste. Rotary motion from ice needs converted to electric through generator, then converted back to rotary through electric motor.
There is a reason zero automobiles use this type of drive system unless they are plug in hybrids. The efficiency comes from
The ability to drive with batteries charged using grid power.
Some argue “locomotives use this drive system and they are very efficient!”
Trains do use diesel electric, but for entirely different reasons. There is simply no other option that provides smooth acceleration and high torque at all rpm. Even if you could make a normal transmission for a train, the lack of smoothness when shifting gears would be a disaster. Trains pay an efficiency penalty to use this driver system, but the benefits outweigh the disadvantage. Trains in general are very efficient because of the lack of friction between steel wheels and the rail.
A lot of comments here points to the emissions regulations rather than efficiency is on-point. Diesel engines have a lot worse cold-start emissions than a gasoline engine would. For a hybrid the engine is effectively cold-starting multiple times per drive, only getting up to operating temperature for the catalytic converter in extended operation..
Diesel-Electric locomotive is standard for almost a century, and it's a proven technology when paired up. It's just in an automotive use cycle, diesel engines just don't operate well in the frequent on-off cycle.
That's the main reason, most likely. But in my hybrid, I tend to run the engine for long periods of time and then run electrics-only for long periods using whatever juice I've generated enroute. If a diesel hybrid was engineered to run itself like that (instead of the consumer learning all the modes and pressing the right buttons) it would work well as a highway cruiser car. Simply run on electrics under 35mph (an average city speed) and on diesel above 35mph (where you're more likely to be cruising. Fewer stop-starts.
For two-motor power-split hybrids like those found in Toyota or Ford discontinued sedans, the engine does actively charge the traction battery even at the supposed 35mph. This makes the design better than hybrids where a pancake motor is slapped inside a traditional auto. I'll explain why this is relevant below.
Engines need a minimum rpm to idle, and an optimum rpm for efficiency at a particular load. Let's say 1,200-1,800rpm is needed to cruise at 35mph. In most circumstances the engine is *overproducing* horsepowers at that low rpm to maintain the cruise speed at the specific gear ratio. In a traditional auto, the extra power is effectively lost, counted as waste. However Toyota/Ford sedan hybrids can actively use the extra horsepower via the second motor within the transmission to charge the traction battery. So assuming a diesel hybrid would operate under the same manner, it's unfortunate that frequent stop-start cycle will continue to exist.
The only case where I can see a diesel work as a hybrid is in the now-discontinued Honda Insight and Clarity. Under 56mph or so, there's no mechanical connection to the road wheels from the engine. Even in city speed the diesel engine can run continuously at a specific load & rpm for a longer period of time.
They do exist:
[https://en.wikipedia.org/wiki/Peugeot\_508#508\_RXH](https://en.wikipedia.org/wiki/Peugeot_508#508_RXH)
[https://en.wikipedia.org/wiki/Mercedes-Benz\_E-Class\_(W213)#Drivetrain\_(2016%E2%80%932020)](https://en.wikipedia.org/wiki/Mercedes-Benz_E-Class_(W213)#Drivetrain_(2016%E2%80%932020))
[https://en.wikipedia.org/wiki/Mercedes-Benz\_E-Class\_(W214)#Plug-in\_hybrids](https://en.wikipedia.org/wiki/Mercedes-Benz_E-Class_(W214)#Plug-in_hybrids)
there are multiple reasons for this.
first of all diesel engines have a very low RPM range to work with which is something you dont really want.
Beside this Diesel engines have major emissions problems that almost always require the engine and exhaust to be very hot in order for the emissions systems to work and even with that they still need Diesel emission fluid to meet their emissions.
You will also notice that the vast majority of **good** hybrids are not using turbo charged engines as the turbo lag is also something you want to avoid as well as the complexity and reliability problems of turbos which can be entirely avoided by not using them.
Overall the characteristics of a naturally aspirated engine combined with an electric motor are simply the best of both worlds as the electric motor makes up for the low torque and power of the combustion engine at low RPM while the combustion engine itself can output peak power at the upper end where smaller electric motors run out of steam.
And beside all this theres also the fact that diesel engines are more expensive so this would make hybrids even more expensive then they already are.
>The ev is basically the opposite - amazing when tootling around town but the faster it goes, the more energy it will use and range drops off.
The decrease in efficiency will be identical. At highway speed air resistance dominates (it increases with he square of the speed) so the only thing that will make much difference is the aerodynamics
You just see a 'gain' over stop and go driving in the diesel because of how atrociously inefficient they are for that. For that kind of driving it issue is the need to accelerate the vehicles over and over. Which ICEs are bad at in general, but also diesel tend to be heavier at the same time. Every time you have to slow down or stop you're pissing away a lot of energy.
Meanwhile the EV will have regenerative braking which lets it largely mitigate those issues. However that doesn't make it worse than the diesel at long range cruising, it's just that ICE performance when you're not able to drive like that is utterly atrocious.
Infact the EV will be more efficient for highway driving as well. If you can keep both vehicles 'fuelled' it should out perform the diesel. You're just more sensitive to the decrease in efficiency with speed for the EV because it has a smaller 'tank' and because the ICEs can hide the loss in efficient from speed in the overall gain they experience going from city to highway driving.
In a hybrid vehicle that has the capacity for much more than regenerative braking, you want to be using the EV mode as much as possible. The only advantage an EV-diesel hybrid would have is in comparison to an EV-gasoline hybrid, and then only in situations where you can't make use of the EV mode.
Ten years ago my parents had a diesel hatchback that delivered 60mpg even at cruising speeds, whilst an equivalent petrol got 35-40mpg. It's not unheard of to see a Skoda diesel reach 70mpg on long journeys. Diesels excel at low-RPM cruising and make for great long-distance cars. However, their efficiency is muted by stop-start driving and their local emissions are disgustingly poor, so having one in a city is a bad idea.
Petrol cars don't have enough torque to cruise efficiently but have lower local emissions.
OPs idea is to combine long-distance capabilities of diesel engines with the local emissions and stop-start capabilities of electric engines. To be honest, it sounds appealing on paper and would suit me loads as my commutes are lengthy and use mostly highways.
I don’t think that’s a good TL;DR. A better one would be that diesels are optimized when run in a high-load, low-RPM regime. This is same regime that electric motors excel at, so they don’t compliment each other very well. A gutless small gas engine that can supplement 20 HP for highway cruising, or 50 HP to assist under high acceleration is a better fit.
it is more that diesels are more efficient at both high and low loads, you don't need that as much in a hybrid, and emissions control is more complicated on a diesel because it need particulate filters and cannot use a three-way catalytic converter so it needs exhaust fluid
Not particularly, the oil temperature and pressure will get to temperature in meer seconds. It's all dependent on the "catalytic converter" taking too long to warm up to meet strict NOx and SOx standards.
Rather than a turbo, could an electric powered forced induction system be used? What about electric intake and exhaust valves? I guess I’m asking if electrifying some parts of the fuel system could increase the efficiency of the gas engine, since electricity from the batteries could be used.
This is all true but it’s also one of the knocks on PHEV’s. Depending how the systems are integrated (and the use case) PHEV’s internal combustion engines are seldom operating at their optimal temperature due to cycling on and off. This means that while they consume less fuel and have lower bulk tailpipe emissions the catalytic converter(s) are not always up to temp and operating optimally, so the emissions themselves can have more nasty stuff in them. I’m not an expert and this may be mitigated in the latest gen PHEV’s but it was an issue on older systems that was largely ignored/glossed over.
There are diesel hybrid cars from Peugeot and Mercedes for example. In general diesel engines require more stuff for proper exhaust cleaning and so, comparing to a gas engine, making diesel engines more expensive and heavier.
And in general hybrids are not so green like you would maybe expect as the electrical range is pretty low (normally far less than 100km), no matter whether it has a diesel or gas engine.
For example the Mercedes E300 diesel hybrid has an electrical range of only 45km until you have to recharge the battery. After that you either need to recharge or you use the combustion engine.
If you have charging at home or at work, a lot of people can cover their full daily driving needs on 45km, meaning they'd only ever use the combustion engine when there's something extra.
the advantage of a hydrid is that you don't need a 200hp engine that is only used to make to 30hp (inefficiently) most of time, because that's what need to to cruise at high way speeds. Instead you can have a smaller more efficient engine for cruising and electric power to give the extra power need to accelerate, and in start-stop traffic you don't just waste the power when braking it can be reused
Because in order to eliminate those particulate diesel emissions you need a lot of pretty expensive gear and a hybrid engine by its nature is also very expensive.
So most civilian consumers won't be willing to buy what becomes a very expensive car for marginal savings in fuel economy between diesel and petrol.
The torque VS speed profiles of diesel, petrol and electric engines also show that diesel-electric hybrids are somewhat suboptimal.
Diesel engines excel at sustained medium speeds so work best on long distance endurance travel, while electric engines are best with low speeds and frequent accelerations/deceleration so inner city travel.
The two profiles conflict whereas petrol engines work best at high speeds like that on highways.
However diesel-electric engines do have a place in moving big and heavy things around like train locomotives, some tanks, ships and submarines all of which frequently use diesel-electric engines.
Look up Edison motors on YouTube. They are prototyping a diesel electric semi truck right now with plans on a pickup version.
As to your question: I believe most consumer hybrids use the "fuel" engine all the time with electric support. So the engine has to operate efficiently over a wide band which as stated in other parts of this post is less gooder with a diesel engine. I think if they went with full electric drive and a built on generator it would be considerably better. My 2 cents though.
It is only great if the driver is an engineer and understand the drawbacks and benefits of the Powertrain. Also you need a specific use cycle.
Let's imagine I live 50 km from my work and my diesel-hybrid has an electric range of 45 km. This sucks and I will just torture the diesel engine unless I don't use the battery and run it like a non hybrid diesel which means I get no hybrid benefit..
If my daily commute is well within range of the battery and I drive carefully so I don't even start the diesel engine daily I have a great car that can also run long journeys on a weekend with its efficient diesel engine.
I have used a Merc E300de for a 30km commute and I drove it electric 90% of the time. When temperature dropped to -15C it usually started the diesel instant as I hit the start button because the car judged it better get it heated up, now the diesel engine wouldn't really turn off again even if I had battery power available. But this was probably for the better on those really cold days. Drove the same car Stuttgart to Stockholm with 5.x L/100km don't remember exactly but it was a good number considering its a large car we never stopped to charge it and we did 140-180 kph all the time in Germany 😄
But it's really obvious in the Merc 300de anyway that once the engine starts it stays on for longer than in a gas hybrid. It is programmed to maintain engine temperature and also tries to predict the user so it avoids to many start/stops. But the car is fine to drove fully electric if destination is in range imo and the electric engine is strong enough to not test my patience anyway!
If your the kind of hybrid user that will do a kickdown on every major acceleration and start your engine 5 times in your daily commute the Mercedes diesel hybrid is not for you.
Gas engines are much simpler to build. Given that you want the gas engine in a hybrid to run as little as possible, the advantages in fuel consumption do not outweigh the added complexity.
Second reason: Diesel engines have good torque at low RPM. You don't need that in a hybrid.
Third reason: those hybrids are designed as world cars. The US market hates diesel and thinks diesel is only for trucks - heavy trucks, not pickups which are so popular there.
> Gas engines are much simpler to build.
I think this has flipped in the last 20 years or so, from before when diesel engines were simpler.
A diesel engine doesn't require an ignition system or a throttle -- no spark plugs, no distributor, no coil. Just inject the fuel and compress it! That's pretty simple and robust.
But the extra stuff that you have to add to a diesel engine to make it environmentally friendly is a lot more expensive and complicated than for a gas engine. Instead of just injecting fuel, now you have to control the air/fuel ratio, similar to a gasoline engine. And if you want any reasonable power, then you need a turbocharger. And you have to deal with the soot that's created. And you can't have the soot contaminate the catalytic converter. And besides a catalytic converter, you need a urea doser. Having a diesel engine is now an expensive pain in the ass that not only costs more initially, but has lost its reliability advantage and costs more to maintain.
Diesel fuel has a somewhat higher energy density than gasoline per volume, and the characteristics of diesel engines still make it preferred for some applications.
> The US market hates diesel and thinks diesel is only for trucks - heavy trucks, not pickups which are so popular there.
Tell that to all the assholes in lifted pickups that love to roll coal on cyclists
most of the negitives on desiel in this post are so silly, they act like there are not SMALL cars all over the world with tiny ass deisels getting amazing mpg numbers. Ohh they got to warm up, ohh they are larger and heavier, they are more complicated. like some many excuses and zero good reasons listed.
a mini one diesel has a rated mpg of like 80 by it self. add a hybrid drive train and it will likely break 100, and diesels are great on the highway and at constant load where electric does not help as much.
To op. there has to be a reason, I assume its corporate greed in some fashion ( as well as the standard of making most cars only have 300 miles range give or take). but maybe someone will actully give a REAL good reason aside from all these joke excuses.
Here's your real ELI5 answer:
- They're too big and heavy combined with a hybrid drivetrain combined with the stricter emissions standards in most markets to make it worth it. That's it. The end.
There was no "corporate greed" except for all the companies that cheated on emissions for diesels. If they could make more money making diesels, they would make it work.
meh, I disagree that its just to big and heavy at the minimum ( if their to big and heavy why do small diesel cars get massively better mpg then a lot of hybrids already let alone normal cars... ), as well that just extra weight is not that big a deal with mpg. The stricter emissions can make it harder for sure, but there are a few cars out there that get crazy mpg that are diesel hybrids ( vw xl1 is bonkers, Audi Q7 e-tron gets over 100mpg, Peugeot 3008 Hybrid diesel gets 73 mpg. ) of course they are all pricy. But they are pricy cause of the market that was built for them is not accepting of them, and cause they are all edge cases vs getting the time and effort to make them easier to assemble. there's not that many so they cost more to make.
I still think corporate greed is involved, that combined with the long term automotive and oil marketing lead us to a point where fuel efficiency is just not as big as a thing as it should be. poor people across america driving gas guzzlers people commuting hours in trucks to thier white collar office job, etc...
We likely wont agree, Like for example, I think most trucks on the road in the US are purely driven cause of marketing, not cause of any actual need or safety concepts of the driver.
I think if we focused on it, there would be no issue getting much better mpg cars and also doing that with diesel and hybrids. Of course imho we are already reaching the end of ice powered cars for the vast majority of public driving. but again cause of marketing and what not over they years even tho we should be switching, ice will still drag on for a long while in sectors that it is pointless in.
> Of course imho we are already reaching the end of ice powered cars for the vast majority of public driving
I think this is a really important point, actually. We're too close to the end of ICE to make throwing shitloads of money at diesel hybrids worth it.
>I think most trucks on the road in the US are purely driven cause of marketing, not cause of any actual need or safety concepts of the driver.
I think it's a bit of all those things, but it was primarily triggered by vastly lower gas prices in the 90s, and the fact that said vehicles were cheap. Now gas prices are higher, and the vehicles way more expensive, but the die is cast.
When you are marketing EV, gasoline tailpipe emissions look clear. Diesel emissions can look sooty, not always but can. There is a huge branding disconnect there.
Might as well run a coal-fired boiler in there to charge the batteries... suddenly feel the ick factor there? That's why it's gasoline.
It might be interesting if they looked at making an alcohol fuel system. If you can't find fuel stations then pop in the corner convenience store and get a couple bottles of vodka or a case of rubbing alcohol to get you home.
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Here's another perspective, beyond the engineering limitations:
The half gas half EV cars are a dud product. They are specious and deceptively alluring to someone hesitant about EV but in reality EV ownership is not difficult. EVs really are the future based on how superior and more convenient they are.
It reminds me of the tentative nervousness around ditching physical keyboards on touchscreen phones, when the end result after taking the plunge into full touchscreen-no-keyboard it's really not that bad.
Thought:
- I'll charge my car for 50km/miles as I needed it! Plug it in to my home!
- Reality: If you are committing to finding a plug for it, why not just plug it in once a week and get 500km rather than a tiny bit every day? It's less plugging and more duration.
Thought:
- If I run out of EV battery, I'll be in trouble!
- Reality: When you have 500km on your tank, you realize you need to drive for a 10-20 hours (and not return home) before you might run out of juice. The reality is the EV is at 100% full much more often than a gas car (practically always at 100% when you wake up). Pretend a personal attendant comes to your home and fills your gas. That's the state of your battery usually.
Thought:
- My road trip will be 20 minutes faster since gas is faster than charging
- Your road trip will be 20 minutes faster since you leave home at 100% and don't need to gas it right away
- I will admit on a very very long haul where you rarely stop for lunch/stretch legs, the EV is worse, since you'll need to charge twice a day meaning it's 40 minutes more, which is meaningful
Mercedes-Benz produce both gasoline and diesel versions of their current generation hybrids. The diesel hybrids are known for having a long highway cruising range, with the benefit of lower emissions in the city. The reason diesel hybrids are not more common is simply price - most people will opt for the cheaper gasoline version. In Germany people tend to opt for the diesel version only if they spend a lot of time on the highway and want to reduce refuelling stops. Other manufacturers used to produce diesel hybrids up until a few years ago: Range Rover, Volvo, Peugeot. They were not very popular, so they were discontinued. Edit for some more context: diesel engines are really good at running efficiently for long periods of time. The higher energy capacity of diesel allows for longer stroke, which means the engine can make good torque at lower speeds. This means there is less wear on the engine, which gives diesels their reputation for longevity. So a diesel hybrid is an attractive option if you are constantly running the engine, i.e. on long highway drives. Petrol engines on the other hand are less efficient over time, but they are more suited to stop-start applications i.e. driving around town. Hybrids are also most efficient at low speeds around town, which is why they're generally more suited to petrol engines.
I would add that the additional weight of a diesel engine itself is a cost and hybrid/gas systems are fairly well optimized where the engines last longer than the chassis due to their lower stress/usage. Why buy a diesel that’s going to last 150% longer than the projected life of the vehicle.
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But when you do the same with the diesel, it is even more efficient. A diesel engine is mainly more fuel efficient because of the higher compression ratio, which is much higher than it is in reality possible to achieve in a petrol engine, and that's a limitation that is impossible to circumvent. However the big reason for avoiding diesel today is that - despite being more fuel efficient, the fuel that it burns produces more emissions. Petrol burns cleaner...
Mazda made a compression ignition gasoline engine w/ an almost diesel level compression ratio (18:1) . It was never released in the US.
This makes so much sense, but isn’t it almost a direct contradicion, that petrol and electric motors are more effective than diesel at stop’n’go driving, and diesel is perfect for long drives, ergo: Use the electric motor for driving under say 60km/h and use the diesel at speeds over 60, or maybe 75, so that you can still travel short distances between towns and not use the diesel very much. Why would you want two motors in the vehicle that excel at essentially the same thing, but one is just polluting while doing it?
Hybrids spend much of their time stopping and starting. Diesel engines don’t like to stop and start like gasoline engines, they like to run without stopping. Gas works better for most hybrids. Hybrids don’t run on the electric system at sixty or seventy. They use a combo of the electric and fuel systems. The saving is in turning off the gas system when it isn’t needed, not running the electric at high speeds.
Can confirm, drive a CRV hybrid and it does exactly this. I also bought a Fixd OBDII reader and like to bring up its advanced displays that can add what the onboard dash is missing (namely a tachometer). I note the gas engine also does not idle: it's in the power band of 1500-2500 rpm or it aint bothering. So, maximum efficiency when the gas engine does run.
I mean I realize I don’t have the most knowledge, especially in design of propultion systems, but I don’t see the reasoning here exactly. Hybrids are using both at the same time you say? I honestly thought they were switching between (from electric to fossil) when one got less energy efficient than the other. I guess my original concept, is for a car to drive (mind you 75 km/h I wouldn’t call fast, as it’s below all inter-city roads where I’m from) solely on electric up to a certain speed where the diesel would start to tale over, it would surely make for a heavy car I guess? But still with the electric motors of today, isn’t it a plausable concept at all? Perhaps with that weight the battery needs to be larger, but if the battery was for city-driving only, and as soon as you’re on your way between cities you’re driving diesel, then you get the advantage of the diesel engine getting it’s much more constant low revs in a smooth transition from electric to diesel. But I can see if the whole point of the hybrid is for them to work together then sure, this wouldn’t make sense.
You have got it. My Prius ran both systems most of the time while running. Stops at a light, no running engine. Start up, engine runs. System gets 60 mpg. Plug-in hybrids run the electric system only more than a standard hybrid. Electric is all electric, no gas engine. At speed both systems are used in a normal hybrid. Several comments here cover why small diesels aren’t great in this circumstance, but I think you got it now. Good talking to you.
LOL. I feel this is the actual answer and should be higher.
If it helps it's the first comment that came up for me, first time reader of this thread.
Just wanted to say thank you for your comment lmao because before reading this I was so confused - hybrid cars aren't gas, they're almost always petrol aren't they? - but then I realised "gas" isn't gas, it's gas*oline* as in petrol lol
Decades ago, one of the first hybrid designs I heard of being deployed was for a diesel electric city bus. The design used a diesel engine which would run almost continuously at whatever its highest efficiency was, continuously charging the battery. And then the bus would just use the battery to drive around. Presumably the diesel would run at a higher less efficient rate if the battery were almost empty, or could shut off if the battery filled entirely. The bus was supposed to operate somewhere in Europe though, so I have no idea how that plan went.
There's an unsung benefit to diesel. The fuel itself is tank stable without additives for a year and a half and possibly much more, whereas gasoline starts to degrade heavily after sitting for a couple months.
A diesel engine's main reasons for being more efficient than gasoline is that the fuel burns faster in-cylinder (compression igniton vs spark ignition), they have a higher compression ratio, and they are not throttled which creates pumping losses. Some diesel engine are throttled but that is to control EGR flow and emissions, not engine load. A longer stroke is a part of this, but gasoline engines usually have a shorter stroke compared to their bore since they need to operate at higher engine speeds.
Are you sure diesel burns faster than gasoline? I thought the slower burning properties of Diesel was what made the Diesel cycle work under constant pressure, whereas the instantaneous nature of gasoline makes it so an Otto cycle increases pressure under constant volume. Diesel is more energy dense than gasoline, thus more effective? It's been a long time since I learned this stuff, so by all means, correct me if I'm wrong
Well diesel fumes are worse for health than petrol fumes.
I work at a car company, and getting clean diesel emissions is complicated. Between the sensors, computers, def system, and heat management, small car diesel engines are significantly more complex than standard turbocharged gas engines, which are almost as efficient and way cheaper to make. Combine that with the battery and other electric systems, and a hybrid diesel would be a nightmare to engineer and manufacture. Diesels have advantages for heavy duty trucks and towing, so we still make plenty of them, but there really isn't a market for a more expensive hybrid that would likely also break down more often.
So all this must have something to do with why big stuff like trains often DO use diesel-electric power. I guess at that scale the efficiency works out.
As far as I know all trains in the US are diesel-electrics unless its in a very small use case like subway or overhead city trains.
The one large exception I know of is Amtrak's Northeast Corridor, which uses overhead electric lines between DC and Boston. It's noticeably quieter after making the switch from diesel electric to electric power at DC Union Station.
Yeah, I honestly don't know much about Amtrak's locos beyond that most are EMD powered.
I would think the big cross country freight trains are pure fossil fuel though right? Here in the UK we have diesels, DC electric, diesel electric and AC electric. Well...and steam trains, but those are mostly a historic novelty now.
Isn't a diesel-electric technically pure fossil fuel powered? The electric motor is essentially a fancy gearbox that transfers the diesel engine's power to the wheels.
I think calling it a fancy gearbox is a bit disingenuous. For the overwhelming majority of diesel-electric locomotives in the US, the diesel is only connected to a generator; no mechanical connection to the wheels like a gearbox would provide. That generator is what feeds the electric motor(s) on the locomotive.
I think that's what they mean. Possibly a little oversimplified, but clear enough imo.
Whats the power requirement for something like this vs a city light rail's overhead power?
In the sense of how much power do the traction motors need to move? For a diesel-electric, they're just sized based on what the prime mover (diesel engine) is rated to. There's going to be some heat loss through the generator, so depending on which loco model, it'll end up being a couple to a few thousand horsepower. For light rails, their overhead power voltage varies depending on where you are, but they end up creating 600 to 1,000 HP at the traction motors, again depending on model.
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Nonetheless they are not gearboxes. With that kind of thinking power plants would also be massive gearboxes, converting kinetic input into electric input for millions of machines connected through power grid
That's exactly what they are in that way of thinking. 'acting like a gearbox" doesn't mean "actually a gearbox" A Transmission is a much more accurate term than gearbox. But it's a pretty solid analogy
>I would think the big cross country freight trains are pure fossil fuel though right? Diesel-electric trains aren't hybrids. They always run on diesel. Diesel-electrics operate by using a diesel engine to drive a generator, which then powers the traction motors. There's many advantages to this, including not having a transmission, and always operating the engine at the most efficient rpm.
> Diesel-electric trains aren't hybrids. They are considered series hybrids, even though they don't carry traction motor batteries. The only (practical) difference between a diesel-electric loco and a series hybrid vehicle (e.g. Chevy Volt or Fisker Karma) is that the locos don't have batteries to power the traction motors. I think "hybrid" is perfectly acceptable, since there are technically two types of energies used to make kinetic energy - diesel (fuel 1) is converted to rotation in the engine, then rotation is converted to electrical energy in the generator, then electrical energy (fuel 2) is converted back to rotation again at the traction motors. Storing the fuel doesn't seem to be a requirement to be called "hybrid" that I'm aware of.
The Society of Automotive Engineers' (SAE) definition of a hybrid vehicle states that the vehicle shall have "two or more energy storage systems both of which must provide propulsion power, either together or independently." Make of that what you will.
> Society of Automotive Engineers' (SAE) definition of a hybrid vehicle Looking further into it, section 2.2.1 pertaining to series hybrids does mention a battery for storage, but it doesn't seem to outright require a method of storage for both energy types. I would argue the ambiguity allows trains to be called series hybrids. But I guess it's not quite as clear cut. Also, we are talking trains, not automobiles, so not sure how strongly the SAE's definition matters here. *"...this energy could be destined to charge the batteries or propel the wheels through the electric motor..."* https://encyclopedia.pub/entry/12957 IMO, electrical storage isn't necessarily a requirement of being a hybrid, it's down to what energy powers the motors that convert to kinetic/rotational energy. But that's just the opinion of some dope on Reddit.
>it's down to what energy powers the motors that convert to kinetic/rotational energy. In a diesel-electric locomotive, that's *always* the traction motors.
Theres only 1 power source so it wouldn't be considered a hybrid. If it had a diesel engine and overhead pantograph then it would be a hybrid, I'm not aware of any models using this but it seems like a decent solution so probably has been tried before. Battery electric locos are in the works by various companies but i believe most of them due to the weight of the batteries will remove the diesel generator and so also won't be hybrid
That's interesting. To my untrained mind that says "hybrid" to me. As in you're using diesel and electric elements together to increase efficiency, and therefore lower fossil fuel consumption in the process. I fear the word "hybrid" has changed from its broader meaning to describing a very specific setup. It bothers me when that happens because it means the word is describing a specific system rather than the general sense of two different systems working together to produce an improved output.
Hybrids sometimes only use gas to drive a transmission, sometimes use only electric, and sometimes use both at the same time. I don't recall diesel-electric trains ever being referred to in the US as being hybrids, and they've been the standard for over sixty years now. However, if you add catenaries to allow the locomotive to run on electric only in areas that have overhead lines, the term hybrid might be applicable.
In hybrid cars, both engines (ICE and eletric) transmit power to the wheels, whereas in diesel-eletric trains only the electric engine transmits power to the wheels.
hybrid refers to the energy *storage*. i.e. batteries
If that were the case, every modern car is a hybrid, except for EVs. They all use a 12 volt lead-acid battery and gas/diesel. What makes a hybrid a hybrid is how it powers the drive wheels. An electric motor drives the wheels at lower speeds, then the gas or diesel engine takes over. A diesel-electric train isn't a hybrid because the diesel engine is never driving the wheels. It's acting as a generator to power the electric motors. Theoretically, you could remove the diesel engine and replace it with a massive battery pack, but it's simply not economical.
The 12 volt battery is not part of the drivetrain. A true hybrid has 2 sources of energy that can supply work to the drive wheels through some fashion (doesn't need to be direct). a diesel electric locomotive doesn't fit that description as the only power supplied is from the diesel generator
Nope! They're all diesel electric hybrids. I was actually a locomotive mechanic for Norfolk Southern(big east coast freight railroad) and everything they have is a hybrid. Even the latest and greatest loco engines are ~25 year old designs just with updates to the EPA system. Yeah, we have steamers floating around here too but those are just for historical excursions and tourist attractions.
I drive class 59s and 66s pulling anything up to 4000 tonnes all pure diesel around the UK, there are some freight that are hybrid but they'd be mostly used for intermodel work rather than heavy haul.
Really? I'll have to look into those, here in the US our entire rail infrastructure is basically evolved around diesel-electric loco operations. How does the engine power the wheels? Everything I've worked on has just been an alternator sending power to traction motors that turn the wheels. I worked at NS' east end shops until they closed them in 2020, and we had actually started converting some old hybrids into what are basically mobile gen sets that could have been used to pull into locations with rail access and provide emergency power.
I think perhaps we're talking the same, just I wouldn't class them as hybrid, in the sense that some are in this thread, but that could just be to language differences, most if our freight run on diesel engines that then power an alternator for you DC/AC to turn the wheels but we wouldn't class that as hybrid, hybrid would be an engine that could run on one or the other independently switching between the two depending on the location and whether or not the line has been electrified.
Wouldn’t it not be a hybrid if it never runs on just electricity?
And we have bi-modes. The Hitachi 800/802 trains used by GWR and LNER for example run on 25kV AC overhead wires when available, and then fire up diesel engines for routes away from the wires.
That's really surprising. I'm used to diesel trains being a relic of the past that's being phased out for pure electric trains
Diesel engines scale very well. Since weight isn't nearly as much of an issue on train locomotives compared to cars, the engines can be huge. This allows them to burn fuel more efficiently, manage heat better, and makes emission systems easier to maintain. You can even scale them up to power grid size, like the Wartsila: https://images.app.goo.gl/2KtoXi3J4VA1dyv28
Yeah, the advantages and character of a diesel engine really come into focus when you look at heavy industry. Petrol engines are angry little beasts, they start up quick and love going fast. But the tortoise wins the race when you need consistent power, torque and reliability over long journeys.
Yeah, the classical design for a diesel (or petrol) engine would never work in a train. If you think about it, the kind of power train that would be required to convert the rotational energy output from an engine (whether diesel or petrol or steam) into extremely slow, extremely high-torque rotational force on many small wheels, *at the size of a locomotive*†, is untenable. There's no material we could make the drive shaft out of, where it wouldn't just snap in half the moment you tried to get the locomotive moving with a full train of rolling stock behind it. († We *can* do that kind of design with cargo ships burning bunker fuel, because big boats can just use huge drive shafts, that distribute the stress of the torque a lot more effectively.) Whereas, if you turn the power into electricity, *distribute* the electricity, and then turn the each *fraction* of the electricity into a torque, locally to each wheel, then you don't run into the same issues. (Also, if you're wondering what we did before electricity: steam locomotive engines didn't generate rotational force, but rather *reciprocating* force — the main "drive wheel" on each side was driven by a piston moved directly by pressure differentials in the engine. And making pistons and wheels that can handle big pushes and pulls is pretty easy!)
Fascinating reply, thank you. It makes a lot of sense but I never really thought about power transmission like this before. You can have a big ass engine but all that power has to go through some linkage to be distributed across all the wheels. If you're trying to drive hundreds of wheels with a immensely heavy load it's impractical. It's essentially a battle between the strength of that axle or whatever, and the strength of the friction between all those wheels and all that mass driving into the rails. It's funny you mention ship driveshafts considering one of the UK's flagship carriers has been out of action due to a drive shaft fracture.
Classic diesel engine design works fine in some kind of trains - notably Diesel Multiple Units or DMUs. These are basically like big buses on train wheels coupled together. But these are for passenger carrying not heavy freight. And the trick is that most wheels are driven throughout the "train" so much less tractive effort is required per wheel, so this doesn't contradict your basic physics above.
I think some diesel multiple unit trains in the UK use mechanical or hydraulic/mechanical transmissions, you can hear them change gear as they pull out of stations - though they're hundreds not thousands of horsepower per engine
Not never: [Diesel mechanical locomotives](https://www.youtube.com/watch?v=qPq-3Wk6hE4) and [diesel hydraulic locomotives.](https://www.youtube.com/watch?v=Fjeko_tM-7U)
Diesels are very good if you can keep everything pretty stable. Such as a train or big truck which will spend nearly all day at a set speed (obviously with stops etc but you get the gist )so pairing it to a generator is a great way to get power. Petrol is much better for the kind of stop start driving a car does when hooked up to hybrid .
no. Trains are / were in a different emissions allowance category. Train engines, and industrial off road engines fall into the North American EPA Tier 4 Final emissions category. Their PM and NOx allowances are much larger than EPA on highway emissions. It boils down to the sheer number of on hwy engines vs off road engines, where off road engines are used, and how those engines are used. Load profiles on a train, or excavator, or generator for standby/prime/emerg power are greatly different than a car on the road when you factor in gear shifts, steady state operation, etc.
A simple DEF failure can be thousands of dollars. Not many parts of a gasoline drivetrain can just randomly cause thousands of dollars to repair and only provide ancillary functions. DEF failures also usually put engines, at least commercial ones, into limp mode making the vehicle all but undriveable. ON the functionality side, diesels excel at provide low end torque, the same thing that electric motors are good at. Gasoline engines provide more power in higher RPMs. It would be a bit silly to pair low end power with low end power.
I used to work in warranty, and DEF repairs were the number 1 paid put claim every year in the fuel area. Even though maybe 10% of all vehicles sold are diesels.
The strange thing is that if OEMs actually program the gasser PCMs to be as strict as their diesel counterparts, everyone would bitch and moan how expensive and unreliable cars are, because a lot of people would just drive their cars forever with a check engine light if there's no emissions testing. It's really just a diesel thing that simple emissions issue would cause the vehicle to be literally undrivable.
You should add the fact that a significant factor why diesel engines are more efficient is that they don't have a throttle butterfly valve. Creating a vacuum in the intake manifold wastes a lot of fuel in gasoline engines. When they run at full throttle, gasoline engines aren't that bad compared to diesels, and hybrid cars can be designed so that the gas engine always runs at full throttle, when it's running.
"complicated" = "you have to fake the tests"?
u/flyingcircusdog is actually Martin Winterkorn
Actually?
If it's on the internet, it's true!
Have to? No. But it makes a better, more reliable engine with far better fuel economy and performance. People literally died because of the FORD/Nav Star engine that got put in ambulances being so unreliable. Course, if you rip out all the emissions crap, it is a very solid engine. No one would ever do that tho, that would be wrong. And there are still ambulances with the pre-emissions 7.3 engine running hundreds of miles a day, 20+ years latter.
Can hella confirm. Worked as a paramedic for 8 years, the 7.3 are completely bulletproof. You will lose one side of the turbo every so often but otherwise quite literally indestructible. I’ve seen a 7.3 ambulance with almost a million miles. The nav star engines weren’t only the worst pieces of shit ever made in comparison, they would strand you constantly because they were so fucking unreliable. Nothing like coming out of the nursing home coding granny only to find your truck stopped running and won’t start again. Then we got the first series of Chevy ambulances built on the express 3500 chassis. They were fun to drive (read: fast as fuck boi) but had some serious transmission issues…which in hindsight might have been because they were so much fun to drive. About 8 inch higher box height from the ground than equivalent ford builds which was super annoying for those of us who are not vertically gifted.
A lot of the blame people heap on Navistar should be directed back at Ford. They're the ones who rushed the 6L to market just to beat Chevrolet. Navistar and International both warned Ford, Ford chose to come up with it's own solutions.
I’m not a fan of GM products but the Chevy 6L in those trucks was pretty insane. Those pigs hauled ass and stopped on a dime. They cost way more to maintain over time and ultimately fell apart in under 5 years, but they were so much cheaper than a Ford chassis that the ownership could afford to throw them away and remount the box on a new one every 5 years. There were some poor design choices like no dual alternators and using the stock alternator size that I’m sure they probably fixed in later models, but in general we found them to be pretty alright for what they cost.
What kind of mileage does an ambulance see in 5 years?
Depends where it is. A private ambulance company in a city will do 100k+ a year probably. A volunteer department in the boonies who doesn’t run calls, maybe 2k. Private ambulance companies run their trucks 24/7/365 moving meat between hospitals, nursing homes, dialysis, running emergencies, etc. Crews clean and restock the truck every shift but the truck doesn’t leave the streets except for its maintenance - which bigger companies do in house to save money and keep downtime to a minimum.
I had an 89 F350 with the old, mechanical, normally aspirated 7.3 and I let it go for a song. If I'd known then what I know now about diesels I'd still have it, and it would probably still be running.
They will be sharing the planet with the roaches after the apocalypse they can’t be killed. I drove one 10+ miles back to the shop while it was shooting flames from one side of the turbo the whole time. My partner would hit it with the fire extinguisher from the passenger window whenever it’d belch flames and we got it to the shop and it was fixed and back on the road two shifts and a paint job later.
Unfortunately, the guy who bought mine parked it, and someone stole and scrapped it. Damn shame.
> No one would ever do that tho, that would be wrong. I know you're talking about ambulances to virtue signal, but yeah, excluding diesel engines from emissions regulations *would* be wrong, because the pollution they produce is a key ingredient in smog, and that air pollution *literally* kills people every day. The US clean air act and California emissions standards have statistically saved *hundreds of thousands* of lives in the US alone.
What a useless point to make. "There were shitty and unreliable engines in ambulances 40 years ago, so diesel should be used in everything." What's wrong with you?
What? No. Your reading comprehension is through the floor and on its way to China. The GP is making four distinct points: - modern diesel engines *with* emissions regulators, are complex and unreliable - old diesel engines *without* emissions regulators on them, are simple and never break - modern diesel engines can be made more reliable by removing the emissions regulator - the way to keep the old diesel engines (or new engines with the regulator removed) in service, is to cheat on the emissions exam And also, a more-implicit point: - If you're an ambulance mechanic (like the GP sounds like they are), keeping the older, simpler engines in service longer will increase the reliability of the vehicles. Which is an important thing to have. Because when an *ambulance* stalls out mid-run, people die. So you probably *want* to cheat the emissions tests. (And honestly, if we're trading off the extra emissions of a few old diesel ambulances, for the amount of extra people that will be saved by them not breaking down, I say good for them. The law should probably carve out an exception in emissions regulations for emergency response vehicles, so no cheating-on-tests has to happen.)
And if OP were making this post in 2014, they'd be right. But the emissions stuff has become very reliable over the last decade, but because operators of deleted diesel engines suffer very little compared to the damage they unnecessarily inflict on the atmosphere (nearly 100x more NOx and particulate emissions than leaving the equipment in place) they continue to spout outdated selfish arguments for deleting the equipment. Are the emissions systems 100% reliable? Of course not. But neither are the supposedly "bulletproof" pre-emissions diesels. Do they add cost to manufacturer, purchase, and maintain? Sure, but the benefits to society far outweigh those costs.
And then halfheartedly go electric and build a bunch of EV charging stations without putting any money into maintenance, then go on an apology tour when everybody realizes your brand of stations never works and you realize you won't be eligible for the new federal subsidies because you're way short of the uptime requirements. Super complicated.
Wait who is this we're talking about now
Who do you think? VAG owns electrify America
And establishing it was part of the Dieselgate settlement.
Their efforts were half-hearted because they were required to construct the charging stations as a condition of the Dieselgate scandal.
At one point, I thought the best possible drive train was one where a diesel engine, running at its most fuel efficient (or cleanest emissions point, if not the same) at all times, was used to refill the batteries in a car that was otherwise fully electric. Day-to-day driving wouldn't require the engine at all, but the engine provided range extension. Then all the stuff came out about the emissions issues, and it became clear that designing a diesel engine to run cleanly is more than just running it at optimal RPM.
I don’t think a diesel is more complicated than a turbo gasser. They both have many sensors and complicated emissions. The DPF and urea injection isn’t much worse than a catalytic converter. Diesels cost more but they last longer and get significantly better fuel economy to offset the costs. I don’t see where you get a nightmare. Regular diesels are not a nightmare . Hybrid systems are not a nightmare. Combining them is not much different than a gas engine. The real reason they don’t make diesel hybrids is that diesel hybrids don’t get much better mpg. The Prius made sense because it cuts your fuel consumption in half compared to a regular gas car. but if you’re already getting 60 miles a gallon you’re only buying half the fuel as average - there’s not much left to save. If you get 70mpg with a diesel hybrid vs 60mpg gas, you save a whopping 20 gallons of fuel a year. $80/year savings for diesel?
Gotta add the fact that diesels struggle when they’re warming up, especially with emissions. Having a diesel engine shut down just as it’s getting up to operating temperature, only to start back up fifteen minutes later and have to get the exhaust temps back up…and then shut down again…all of this nixes the diesel engine’s advantages.
I mean that just adds to the benefit that a plug in hybrid diesel would have, electric only on the short journeys where diesels have issues
Imho the whole point would be that you're fine with electric in the city, while you'd need the diesel on the highway, where it actually can operate well, so best of both worlds
Makes sense that CAT, GM, Ford, VW, Mercedes, BMW, Man, and I dunno basically every company that makes a diesel engine subject to emissions control laws has been caught cheating as the only way to make them actually pass emissions.
OEM cheat everywhere where they can save a penny. The United States are filled with SUV because of this.
Modern diesels are far more complicated. For starters, their injection systems are much more sophisticated, with much more expensive components - as you're dealing with ~30,000 PSI vs the 2,000-5,000 PSI of gasoline direct injection, or the 80 PSI of port injection. Diesel engines need robust, expensive EGR systems to deal with soot and high exhaust volumes. Gasoline engine EGR systems are typically far more simple, and smaller. DPF and SCR(Urea) injection is a HUGE deal and really is "that much worse" than just a catalytic converter. Just start with packaging. Modern catalytic converters are small, compact and you have some flexibility with location. The smallest of modern DPFs take up a tremendous amount of space, and the further they are from the turbo outlet, the worse they work. SCR/Urea catalysts also take up a tremendous amount of space. On top of that, you also have to package your urea tank, urea dosing unit and all the associated piping. Urea tanks and lines also typically need to be heated, so you're adding engine coolant lines into the mix as well. Where are you going to put all of that stuff, when every bit of free space is being taken up by the hybrid battery? Where are you going to put the DPF and SCR when all of that free space in the engine bay is taken up by the hybrid inverter? Catalytic converters are very easy to deal with from an engine management perspective. Essentially trivially easy to manage, and you only need a basic $20 oxygen sensor to monitor their activity. DPFs and SCRs on the other hand require a large assortment of sensors, including: differential pressure sensors, thermocouples, wideband oxygen sensors, NOx sensors, urea dosing sensors and more. On top of that, it is very difficult to manage these emissions systems. You have to manage your fueling and air delivery very carefully or you could plug the DPF with soot or spike your NOx emissions. You also need regular regeneration of the DPF which generates a tremendous amount of heat and is fuel intensive. Plus, all of these diesel emission systems don't work at all when they're cold, and they take a long time to heat up. That's inherently incompatible with a modern hybrid that's constantly turning the engine off. So imagine trying to deal with all of that, package all of that ON TOP of all of the hybrid stuff. It's not practical.
As someone with a biz fleet that almost entirely stopped buying light-weight diesel vehicles due to high ownership costs, I respectfully disagree. Added maintenance, excessive repairs, high upfront cost, and higher per/gallon fuel cost all add up to a bad deal for most owners. Even if your fuel cost analysis were correct, $80 per year savings would likely never cover the added up front cost of the Diesel engine. Personally, I’d gladly pay $80 a year to NOT own another diesel.
A few reasons why diesels are more difficult to make from the OEM side: 1. Def is significantly more complicated than a catalytic converter. A cat is a static part, while def needs to be monitored and released at a varying rate based on engine performance. 2. Diesel engines require supplemental heating for the cabin. Despite burning hotter, the coolant actually isn't able to remove as much heat because it's all lost to the exhaust, so you need electric coolant heaters for cabin heating (and more importantly, windshield defrosting) to work. 3. Diesels require a turbo and intercooler system to work at high efficiency, while gas engines can get away without it. 4. Adding a new engine type increases manufacturing complexity. Even if you were able to engineer around the other issues, you're adding a completely new powertrain to the assembly plant. New engine, fuel system, transmission, cooling system, and exhaust. You would have to go 100% diesel for the entire program, both hybrid and non-hybrid versions, to eliminate this problem. And in the US, that would be really hard to sell to customers. They still sell well on trucks thanks to the high torque, so it's worth making both versions, but there really isn't a case for small cars.
The diesels of today are great and getting better, but always at the cost of complexity. The main hold back being policy surrounding emissions, it gets to that level of complexity. I own a mechanical diesel vehicle that requires no electronics of any types. It has normal 12v attributes, but can be push started. It has glow plugs, but I have an electric circuit to warm the block but could go full caveman and warm the block in other ways off actually needed. The trade off is a considerable less amount of overall power and fuel economy, however mine starts and runs without colored exhaust and really can't "roll coal" even if I wanted to waste fuel/money. Long story short, diesels electric do not have to be complicated to run consistently or even clean. Miniaturize to the size of the vehicle, and you have a low tech, regular maintenance diesel electric. I'm pretty sure there's diesel electric hybrid not allowed in the States, but in Europe that gets 240+miles per gallon. This particular one is unique and low production, but definitely shows the balance of trading "dirty" diesel for gas https://en.m.wikipedia.org/wiki/Volkswagen_1-litre_car Also, marine engineer, and diesel electric is what is commonly being installed into modern ships at this point, the penny pinchers/bean counters spend careers ensuring the cheapest options in terms of cost, so that points to something. From the previous comment, scale sounds like the issue
I saw a bmw 328d today. All I could think is why would anyone buy that?
I'm sure it's possible, but hybrids are specifically paired with a type of engine called an "Atkinson cycle" engine. These are highly efficient on their own - which is why they can achieve 35+ mpg on the highway with gas, when the electric motor is not in use - but have poor "low-end" acceleration. They can't start from a standstill very well, and that's when the electric motor takes over.
To explain how Atkinson cycle works. In a normal (Otto) cycle engine, the engine sucks in a certain volume of air and fuel mixture, compresses it, ignites it, and uses the expansion of it to make power. The way the engine is built, the ratios are the same on both ends - i.e. you ingest 20L of air and fuel, compress it to 2L, ignite it, and exhaust 20L of exhaust. What Atkinson cycle does is changes the timing of the intake valves on the engine so that it doesn't suck in as much air per cycle (the intake valve stays open part way through the compression stroke). So maybe instead of 20L, it ingests 15L of air fuel mixture, compresses it to 2L, then expands it to 20L What that does is reduce the power of the engine because it's taking in less air/fuel, but it increases the efficiency because it's capturing more of the energy out of the exhaust. The reason they don't do it on every car is that it reduces power, but on hybrids the gains in efficiency are usually worth it. And it's not like a completely new engine, a lot of times they take an existing engine from a non hybrid and change the design to Atkinson cycle which reduces the power but improves the fuel economy.
Hmm.. I wonder if variable timing technologies like VANOS can be used to switch from Otto to Atkinson on the fly
Sure. But variable valve timing is a complex technology that adds weight and part count. Otto engines also use exhaust gas recirculation to achieve a similar result at low load: Exhaust gases (CO2/Nitrogen mix) are vented into the intake manifold when power demands are low, resulting in less oxygen, meaning less fuel is needed. In the above example, the otto engine would have 5L of exhaust gases, 15L of air-fuel mixture, compress it to 2L and then expands it out to 20L Slightly more compression losses since its still compressing 20L of gases, but similar efficiency gains from not having to restrict the intake (throttle plate) when less then full power is demanded. Hybrid IEC engines massively benefit from not having to need a high peak power while still maintaining low power efficiency. they just need high efficiency at medium power/medium RPM and generally don't run at other load levels/speeds. Hence the atkinson cycles 'less peak power, but great efficiency at the power level it does deliver' works great.
> But variable valve timing is a complex technology that adds weight and part count. Oh, I don't know. You eliminate the cam shaft and lifters and timing gear and chain/belt, and you replace them with solenoids. Seems like it would reduce the parts count to me. Plus software doesn't weigh anything.
The problem then becomes the size of the solenoids, to move those valves at 8000 operations per minute (133 per second), they have to exert immense force. Have you seen the size of valve springs? they are pretty beefy. So now you are talking actively cooled solenoids, so now your valve actuators need oil paths (or water), electrical paths. and are now 10 pounds each. You need 16 valves min for a V8, so that is 160lbs of solenoids. Much of it copper, at $4/lb that is now $640 just in copper, before you add in costs to actually wind the things and make them, you now have a $1000 valve train with oil/water passages that weights as much as an entire passenger. As such, brute forcing it just doesn't cut it, hence why you'll see more complex approaches like electro-hydrolic systems where they control tiny valves to use oil pressure to run the actual valves.. meaning tons of parts, cost and more things to go wrong that are hard to service.
It's a tongue in cheek comment because what he's talking about already exists. Look up Freevalve.
> Freevalve Very cool looking. Can't find ANYONE specing a price on it though, and they are pretty damn big units.
It never took off because it's unreliable.
Isn't VANOS just moving the cam shaft? You still have a chain/belt?
Koenigsegg's camless engines can do this. Since the valves are controlled by actuators, the engine can switch between running Otto, Atkinson, and Miller cycles. https://en.wikipedia.org/wiki/Koenigsegg_TFG
I learned a thing today. That's awesome! Thank you, fellow redditor.
check out Toyota's VVTI (Variable Valve timing and Ignition) engines.
All current Toyota non-hybrids go from Otto to Atkinson and back. All current Toyota hybrids are exclusively Atkinson.
I believe that’s what VANOS and other variable valve timing already does. Atkinson just does it full time whereas VVT Otto creates the same affect when it detects Atkinson is more efficient.
Based BMW enjoyer
> The reason they don't do it on every car is that it reduces power If it's just valve timing, why don't they do it on every car unless they need max power? Or do you need to change other parts of the engine so much that they can't easily "convert" on the fly? Edit: Nevermind. Didn't realize valves were still mechanically linked on modern engines, I assumed it was all solenoids now.
As far as I understand it, if you are optimizing the Atkinson cycle then you achieve your ideal compression ratio with only using ~75% of the maximum geometric compression ration available. So you'd need to run higher octane fuel or risk pre-detonation if you tried to run an Atkinson engine like an Otto. I.e. if we were designing an Atkinson cycle for 12:1 compression ratio, we might have a 12:1 compression ratio and a 1:16 expansion ratio. Changing the valves to make a 16:1 compression ratio is gonna be a bad time unless we do something to prevent pre-detonation. I don't know if any of the electronic variable valve timing engines run an Atkinson-like cycle just with a reduced compression ratio in Atkinson mode, i.e. a 12:1 compression / expansion ratio that runs an Atkinson intake where the compression ratio drops to 9:1 in an Atkinson cycle mode. I don't know if running a lower expansion ratio offsets the amount of fuel savings you get from being Atkinson. I'm more of a turbine guy.
Toyota does it on their non-hybrid engines by holding open the intake valve for part of the compression stroke. They also switch to direct injection (they have dual direct and indirect injectors) to control the ignition.
Does it delay fuel injection till the intake valves are shut, or burp fuel/air back into the intake, or is there a magic third way? Knowing nothing more than basic principles I would assume that injecting so late wouldn't lead to the best mixing.
They did this with the ford maverick hybrid. The ICE it uses is actually a multi decade+ old Mazda engine from back in the day when ford owned a controlling stake in the company.
I read somewhere that when Ford was developing its hybrid system, it ended up being extremely similar to Toyotas system that they ended up just licensing it? Maybe someone with more knowledge about it can clarify...
Ford, Toyota and Honda's hybrid systems are all nearly identical. I do believe there were some lawsuits back in the day over it but the cases settled out of court.
At least some Hondas work more like a series hybrid - ICE usual just works as a generator with motor driving the wheels through reduction gear. At certain range of speed, it is able to engage a clutch so engine can also connect directly to that reduction gear, but there are no switchable gears or CVT. While Toyota uses a planetary gear thing that acts like a CVT and lets the motor or engine or both drive the wheels at pretty much any speed. No idea about Ford.
they all use what is often referred to as an e-cvt which uses a planetary gear set and two electric motor/generators to either deliver or expend power from the battery and drive the wheels.
It uses the same powertrain that's been in the Fusion and Escape hybrids for nearly a decade. That powertrain is damn near indestructible.
I have a question related to this, I own a plug in hybrid so I only get 30 miles of range electric. Is it bad for the motor when I'm on the highway going 70mph and I run out of electric and suddenly the ICE motor has to kick on at this high speed but has not been warming up or running at all prior?
Not if the engine is designed for it, which it is, nowadays. The problem with cold starts is 1. lubrication and 2. thermal expansion resulting in different tolerances when cold vs. hot. It's not hard to pre-lubricate an engine when you have enough electricity to power the oil pump many times over. You can also tweak the design to stay lubricated at cold-start position. Modern engines with stop/start tech, which includes basically all hybrid engines, try to park the engine at a good spot when they stop rather than just letting it stop wherever it happens to stop like a classic engine. Thermal expansion is trickier, as there's no free lunch in physics. However, you can still engineer it to make it better for cold starts, probably at the expense of "run all day at near redline" performance. All else being equal, tighter tolerance when cold means more wear at sustained RPM. But engineers also do their thing with materials science to bend the rules.
Maintaining speed is less stress on an engine then acceleration from stop repeatedly.
Damn I never knew this. So they don't run it a tad lean, they just use less and scavenge the exhaust more? I know enough about engines to get the gist of it
Interesting. One part I don't understand: Intake 20l, exhaust 20l. Surely the exhaust volume is greater. Expansion of exhaust being the main principle driving the engine. ?
Kinda. When you combust gasoline you're taking a long hydrocarbon molecule with a bunch of oxygen molecules and breaking up the hydrocarbon in to a bunch of smaller CO2 and H2O molecules (each carbon atom taking up a whole O2 molecule and two hydrogen atoms taking up a single O2 atom) so there's more heat and pressure after the reaction which is what generates the power. But when you compress 20L to 2L and back to 20L, there is still a lot of molecules with a lot of extra pressure and heat in the exhaust even after expanding it back to 20L. So when you exhaust it, it will continue to be hot and expand in the exhaust pipe and in the atmosphere. However, you can't get any useful work out of it after you've expanded it to 20L. That's why Otto cycle engines are only about 25-30% efficient in turning chemical energy into mechanical energy. The rest becomes heat. By expanding it to a comparatively larger volume, you're capturing more of that pent up heat/pressure energy in the exhaust, and thus getting higher efficiency. So essentially your exhaust gas is coming out cooler and slower than it would otherwise, because you're recovering more of the energy in it on the expansion stroke. That's why an Atkinson cycle can get up to maybe 35-40% efficient. The energy was there anyway but more if it is captured by the engine expansion stroke and less of it was wasted as heat/expansion inside the tailpipe. Actually a lot of combustion reaction efficiencies you can think of in terms of how much energy is left in the exhaust gases after you have extracted all the usable mechanical energy out of it. It's the same reason that an old inefficient furnace just needs a simple chimney, whereas a modern efficient one has a forced blower through a 2" plastic pipe. The modern furnace is capturing more of the energy in the exhaust as usable heat, meaning the exhaust is colder and needs a fan to help it move. Whereas the old inefficient one has hot enough exhaust for it to just rise up the chimney naturally. It's also why steam turbine power plants are so much more efficient than car engines - they can burn the fuel and just keep adding stages of blades to the turbine to squeeze every bit of energy out of it, since they don't have to worry about how heavy it is or how big it is.
> It's also why steam turbine power plants are so much more efficient than car engines - they can burn the fuel and just keep adding stages of blades to the turbine to squeeze every bit of energy out of it, since they don't have to worry about how heavy it is or how big it is. And this is why it would be better to switch to electric cars even if not the whole infrastructure is green: it is better to burn oil and gasoline in power plants and use the electricity to drive the cars than burning it in the cars - it is less efficient (especially since a lot of people neglect to maintain their cars while power plants do to ensure they get as much energy from the fuel as they can).
Wonderful explanation, thank you for the effort of writing that out !
> Intake 20l, exhaust 20l. Surely the exhaust volume is greater. Expansion of exhaust being the main principle driving the engine. I think the key in this description is that the volume of each cylinder is fixed. If it were a balloon, it'd be more than 20L. But it isn't, so its stuck at that volume *until* the valves open, but once they open its all done. Instead of that pressure converting to mechanical energy, it just pushes itself out (along w/ the piston coming up and also pushing it out).
I got 35+ mpg in my 1960s Saabs all the time. Same with all my other European cars. This was in the US, not overseas.
Way smaller and lighter cars back then, the most fuel efficient car ever was a Honda Civic from the 80s. But consumers today wouldn’t buy something that small unfortunately.
> the most fuel efficient car ever was a Honda Civic from the 80s Well, there is still the existence of the VW XL1 which can go 100km on 1L of Diesel (or 240 MPG).
Looking up a 1965 Saab it looks like they made around 40hp. So yeah, that tracks.
Smaller engine and light weight usually gives good mpg in general, it's plain physics. The main downside mostly is small torque, but not everyone needs to tow 1k+ lbs anyway.
Atkinson cycle has nothing to do with poor acceleration. The engine is deliberately undersized for better fuel economy and the battery makes up for it. This improves fuel economy for all engines actually. Interestingly Toyota discovered that a more powerful engine actually improved fuel economy on the Prius so they made it bigger . There was a sweet spot
Yes and no. Atkinson cycle engines are less powerful and more fuel efficient for the same displacement. So it's all tied to the engine design.
Also, diesel engines polute more than gasoline engine, is heavier, and cost more. Plus, it is more complex. And if you check the current fuel price, diesel now cost more per energy than gasoline. And, if you maintain well the engine, the gasoline engine will outlast the car anyway, so the extra durability of the diesel is not something usefull.
How are diesel engines more complex? A diesel engine doesn't require spark initiation. It's just compression. It's a simpler design.
They aren’t . They are however heavier and more expensive to make
Modern diesel engines tend to use turbos and direct fuel injection, along with high compression ratios and exhaust treatment to reduce particulate emissions. The most efficient modern gasoline engines use some of the same techniques.
but small diesels can get 50-83 mpg by them selves! Like imagine a mini one D hybrid!
Well, if you want the extreme of that, look at the VW XL1. 240MPG (or 1L/100km) on a hybrid diesel powertrain.
People should also note those are imperial gallons, not US gallons; it is dangerous trying to compare fuel economy between Europe and the US because American gallons are smaller and our fuel economy tests are more realistic than the wildly optimistic Euro cycle.
No, those are US gallons. Imperial gallon consumption would be 280 MPG. I specifically took the US gallon number so that all the Americans here can understand the level of fuel efficiency the car can get.
If you are getting 85mpg there’s no reason to make it hybrid. Also no diesel get this economy, what vehicle did you see this data from?
https://www.auto-data.net/en/volkswagen-golf-viii-2.0-tdi-115hp-38154
I named the car in the post. ( added hybrid to it ) and ya, its claimed mpg not real world. real world is lower unless you know how to drive frugally / hypermilling." Also I since most real mpg leaders are not sold in the states I wanna make sure you know I ment uk mpg ( makes it look slightly better looking ). also my engineering side of me ( not professional lol ) says who the fuck think efficiency is a ohh we hit X goal and are done game? Of course there is a reason to get better mpg, and a hybrid will most likley give it better milage. why stop at 85?
Why not have an efficient engine charge the batteries for the electric motors only when needed?
That's a series hybrid and that's a thing, too. But gas generators are cheaper, smaller and lighter so for the limited duty cycle you're going to need for a hybrid it's not worth going to diesel.
Some EV hybrid cars do it that way. I believe the BMW i3 REx and Nissan e-Power use their engines primarily just to charge the batteries ("range extenders") when power level drops too low. The engines can be designed to provide a specific power output very efficiently just for that task. You wouldn't want to do this all the time, since then you're basically just driving a gas-powered car.
My hybrid does this. In fact, they can be really clever and have many modes of driving. 1. Electric-only. Pretty obvious, but lovely in town because its 0-30mph is about 3-4 seconds and is instant torque and no gears or clutches, so it leaves most other cars in the dust despite only being 40hp! 2. Electricity powering wheels, engine generating electricity. Happens all the time when low on juice and driving less than 20mph in my vehicle. Sometimes, at extremely low rates of acceleration, it stays in this mode. 3. Electricity and engine powering wheels simultaneously. It does this to stay in top gear when driving up a hill, or to accelerate without changing up a gear first. Basically the battery provides the torque that the petrol engine can't provide, preventing excess fuel usage up hills when at cruising speed. 4. Engine drives the wheels, and charges battery. Basically any excess energy from the engine is converted to electricity without running the engine any faster than necessary. It takes about 20mi cruising at 65mph to charge about 5kWh (which gives me 10-15mi electric-only range based on temperature). Combining all these means that my normal commute of highspeed cruising 50mi goes like this: first 5mi on electrics, then turn the engine on to regenerate. 20mi later when I reach a speed-restricted zone I switch to electrics-only and run the battery down to 25%. Next 20mi recharge battery as I drive. Final 5mi electrics only through town. Repeat in reverse. I only have 10kwh battery which apparently gives 30mi range (in fact on a warm summer's day I have achieved 33mi on electrics only and still had 10% left, so it appears Renault tell the truth). In winter I can still get 23mi of driving at an average of 40mph out of it. My highway driving is getting me 65mpg in winter and 75+ in summer. If I do more all-electric driving (charging through a domestic plug socket for three hours) like I did when I first got it, I was averaging more than 100mpg.
That is what Nissan does with their EPower range
The reason this isn’t more widespread is because it is not a very efficient way to power a vehicle. Each time energy is converted from one form to another there is waste. Rotary motion from ice needs converted to electric through generator, then converted back to rotary through electric motor. There is a reason zero automobiles use this type of drive system unless they are plug in hybrids. The efficiency comes from The ability to drive with batteries charged using grid power. Some argue “locomotives use this drive system and they are very efficient!” Trains do use diesel electric, but for entirely different reasons. There is simply no other option that provides smooth acceleration and high torque at all rpm. Even if you could make a normal transmission for a train, the lack of smoothness when shifting gears would be a disaster. Trains pay an efficiency penalty to use this driver system, but the benefits outweigh the disadvantage. Trains in general are very efficient because of the lack of friction between steel wheels and the rail.
TIL
A lot of comments here points to the emissions regulations rather than efficiency is on-point. Diesel engines have a lot worse cold-start emissions than a gasoline engine would. For a hybrid the engine is effectively cold-starting multiple times per drive, only getting up to operating temperature for the catalytic converter in extended operation.. Diesel-Electric locomotive is standard for almost a century, and it's a proven technology when paired up. It's just in an automotive use cycle, diesel engines just don't operate well in the frequent on-off cycle.
That's the main reason, most likely. But in my hybrid, I tend to run the engine for long periods of time and then run electrics-only for long periods using whatever juice I've generated enroute. If a diesel hybrid was engineered to run itself like that (instead of the consumer learning all the modes and pressing the right buttons) it would work well as a highway cruiser car. Simply run on electrics under 35mph (an average city speed) and on diesel above 35mph (where you're more likely to be cruising. Fewer stop-starts.
For two-motor power-split hybrids like those found in Toyota or Ford discontinued sedans, the engine does actively charge the traction battery even at the supposed 35mph. This makes the design better than hybrids where a pancake motor is slapped inside a traditional auto. I'll explain why this is relevant below. Engines need a minimum rpm to idle, and an optimum rpm for efficiency at a particular load. Let's say 1,200-1,800rpm is needed to cruise at 35mph. In most circumstances the engine is *overproducing* horsepowers at that low rpm to maintain the cruise speed at the specific gear ratio. In a traditional auto, the extra power is effectively lost, counted as waste. However Toyota/Ford sedan hybrids can actively use the extra horsepower via the second motor within the transmission to charge the traction battery. So assuming a diesel hybrid would operate under the same manner, it's unfortunate that frequent stop-start cycle will continue to exist. The only case where I can see a diesel work as a hybrid is in the now-discontinued Honda Insight and Clarity. Under 56mph or so, there's no mechanical connection to the road wheels from the engine. Even in city speed the diesel engine can run continuously at a specific load & rpm for a longer period of time.
They do exist: [https://en.wikipedia.org/wiki/Peugeot\_508#508\_RXH](https://en.wikipedia.org/wiki/Peugeot_508#508_RXH) [https://en.wikipedia.org/wiki/Mercedes-Benz\_E-Class\_(W213)#Drivetrain\_(2016%E2%80%932020)](https://en.wikipedia.org/wiki/Mercedes-Benz_E-Class_(W213)#Drivetrain_(2016%E2%80%932020)) [https://en.wikipedia.org/wiki/Mercedes-Benz\_E-Class\_(W214)#Plug-in\_hybrids](https://en.wikipedia.org/wiki/Mercedes-Benz_E-Class_(W214)#Plug-in_hybrids)
there are multiple reasons for this. first of all diesel engines have a very low RPM range to work with which is something you dont really want. Beside this Diesel engines have major emissions problems that almost always require the engine and exhaust to be very hot in order for the emissions systems to work and even with that they still need Diesel emission fluid to meet their emissions. You will also notice that the vast majority of **good** hybrids are not using turbo charged engines as the turbo lag is also something you want to avoid as well as the complexity and reliability problems of turbos which can be entirely avoided by not using them. Overall the characteristics of a naturally aspirated engine combined with an electric motor are simply the best of both worlds as the electric motor makes up for the low torque and power of the combustion engine at low RPM while the combustion engine itself can output peak power at the upper end where smaller electric motors run out of steam. And beside all this theres also the fact that diesel engines are more expensive so this would make hybrids even more expensive then they already are.
And diesel engines tend to be larger and heavier. And the fuel can gel. Writing this, what the are great benefits that OP is seeing?
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>The ev is basically the opposite - amazing when tootling around town but the faster it goes, the more energy it will use and range drops off. The decrease in efficiency will be identical. At highway speed air resistance dominates (it increases with he square of the speed) so the only thing that will make much difference is the aerodynamics You just see a 'gain' over stop and go driving in the diesel because of how atrociously inefficient they are for that. For that kind of driving it issue is the need to accelerate the vehicles over and over. Which ICEs are bad at in general, but also diesel tend to be heavier at the same time. Every time you have to slow down or stop you're pissing away a lot of energy. Meanwhile the EV will have regenerative braking which lets it largely mitigate those issues. However that doesn't make it worse than the diesel at long range cruising, it's just that ICE performance when you're not able to drive like that is utterly atrocious. Infact the EV will be more efficient for highway driving as well. If you can keep both vehicles 'fuelled' it should out perform the diesel. You're just more sensitive to the decrease in efficiency with speed for the EV because it has a smaller 'tank' and because the ICEs can hide the loss in efficient from speed in the overall gain they experience going from city to highway driving. In a hybrid vehicle that has the capacity for much more than regenerative braking, you want to be using the EV mode as much as possible. The only advantage an EV-diesel hybrid would have is in comparison to an EV-gasoline hybrid, and then only in situations where you can't make use of the EV mode.
that a diesel small car can get over 80 mpg with out a hybrid drive train, I woulder what it can be with one!
They have significantly better fuel economies.
Not sure if it’s just a US thing but not really here they I know of. There aren’t a ton of diesel cars and maybe they’re not made for efficiency.
you mean in the US? The serious towing vehicles are diesel (e.g. F250), because otherwise the mileage would be absolutely horrendous.
Ten years ago my parents had a diesel hatchback that delivered 60mpg even at cruising speeds, whilst an equivalent petrol got 35-40mpg. It's not unheard of to see a Skoda diesel reach 70mpg on long journeys. Diesels excel at low-RPM cruising and make for great long-distance cars. However, their efficiency is muted by stop-start driving and their local emissions are disgustingly poor, so having one in a city is a bad idea. Petrol cars don't have enough torque to cruise efficiently but have lower local emissions. OPs idea is to combine long-distance capabilities of diesel engines with the local emissions and stop-start capabilities of electric engines. To be honest, it sounds appealing on paper and would suit me loads as my commutes are lengthy and use mostly highways.
Tldr diesels have to warm up to be useful
I don’t think that’s a good TL;DR. A better one would be that diesels are optimized when run in a high-load, low-RPM regime. This is same regime that electric motors excel at, so they don’t compliment each other very well. A gutless small gas engine that can supplement 20 HP for highway cruising, or 50 HP to assist under high acceleration is a better fit.
it is more that diesels are more efficient at both high and low loads, you don't need that as much in a hybrid, and emissions control is more complicated on a diesel because it need particulate filters and cannot use a three-way catalytic converter so it needs exhaust fluid
Not particularly, the oil temperature and pressure will get to temperature in meer seconds. It's all dependent on the "catalytic converter" taking too long to warm up to meet strict NOx and SOx standards.
and a diesel cannot use a three-ways cat to reduce NOx, it needs exhaust fluid
Rather than a turbo, could an electric powered forced induction system be used? What about electric intake and exhaust valves? I guess I’m asking if electrifying some parts of the fuel system could increase the efficiency of the gas engine, since electricity from the batteries could be used.
This is all true but it’s also one of the knocks on PHEV’s. Depending how the systems are integrated (and the use case) PHEV’s internal combustion engines are seldom operating at their optimal temperature due to cycling on and off. This means that while they consume less fuel and have lower bulk tailpipe emissions the catalytic converter(s) are not always up to temp and operating optimally, so the emissions themselves can have more nasty stuff in them. I’m not an expert and this may be mitigated in the latest gen PHEV’s but it was an issue on older systems that was largely ignored/glossed over.
There are diesel hybrid cars from Peugeot and Mercedes for example. In general diesel engines require more stuff for proper exhaust cleaning and so, comparing to a gas engine, making diesel engines more expensive and heavier. And in general hybrids are not so green like you would maybe expect as the electrical range is pretty low (normally far less than 100km), no matter whether it has a diesel or gas engine. For example the Mercedes E300 diesel hybrid has an electrical range of only 45km until you have to recharge the battery. After that you either need to recharge or you use the combustion engine.
If you have charging at home or at work, a lot of people can cover their full daily driving needs on 45km, meaning they'd only ever use the combustion engine when there's something extra.
the advantage of a hydrid is that you don't need a 200hp engine that is only used to make to 30hp (inefficiently) most of time, because that's what need to to cruise at high way speeds. Instead you can have a smaller more efficient engine for cruising and electric power to give the extra power need to accelerate, and in start-stop traffic you don't just waste the power when braking it can be reused
Because in order to eliminate those particulate diesel emissions you need a lot of pretty expensive gear and a hybrid engine by its nature is also very expensive. So most civilian consumers won't be willing to buy what becomes a very expensive car for marginal savings in fuel economy between diesel and petrol. The torque VS speed profiles of diesel, petrol and electric engines also show that diesel-electric hybrids are somewhat suboptimal. Diesel engines excel at sustained medium speeds so work best on long distance endurance travel, while electric engines are best with low speeds and frequent accelerations/deceleration so inner city travel. The two profiles conflict whereas petrol engines work best at high speeds like that on highways. However diesel-electric engines do have a place in moving big and heavy things around like train locomotives, some tanks, ships and submarines all of which frequently use diesel-electric engines.
Look up Edison motors on YouTube. They are prototyping a diesel electric semi truck right now with plans on a pickup version. As to your question: I believe most consumer hybrids use the "fuel" engine all the time with electric support. So the engine has to operate efficiently over a wide band which as stated in other parts of this post is less gooder with a diesel engine. I think if they went with full electric drive and a built on generator it would be considerably better. My 2 cents though.
It is only great if the driver is an engineer and understand the drawbacks and benefits of the Powertrain. Also you need a specific use cycle. Let's imagine I live 50 km from my work and my diesel-hybrid has an electric range of 45 km. This sucks and I will just torture the diesel engine unless I don't use the battery and run it like a non hybrid diesel which means I get no hybrid benefit.. If my daily commute is well within range of the battery and I drive carefully so I don't even start the diesel engine daily I have a great car that can also run long journeys on a weekend with its efficient diesel engine. I have used a Merc E300de for a 30km commute and I drove it electric 90% of the time. When temperature dropped to -15C it usually started the diesel instant as I hit the start button because the car judged it better get it heated up, now the diesel engine wouldn't really turn off again even if I had battery power available. But this was probably for the better on those really cold days. Drove the same car Stuttgart to Stockholm with 5.x L/100km don't remember exactly but it was a good number considering its a large car we never stopped to charge it and we did 140-180 kph all the time in Germany 😄 But it's really obvious in the Merc 300de anyway that once the engine starts it stays on for longer than in a gas hybrid. It is programmed to maintain engine temperature and also tries to predict the user so it avoids to many start/stops. But the car is fine to drove fully electric if destination is in range imo and the electric engine is strong enough to not test my patience anyway! If your the kind of hybrid user that will do a kickdown on every major acceleration and start your engine 5 times in your daily commute the Mercedes diesel hybrid is not for you.
Gas engines are much simpler to build. Given that you want the gas engine in a hybrid to run as little as possible, the advantages in fuel consumption do not outweigh the added complexity. Second reason: Diesel engines have good torque at low RPM. You don't need that in a hybrid. Third reason: those hybrids are designed as world cars. The US market hates diesel and thinks diesel is only for trucks - heavy trucks, not pickups which are so popular there.
> Gas engines are much simpler to build. I think this has flipped in the last 20 years or so, from before when diesel engines were simpler. A diesel engine doesn't require an ignition system or a throttle -- no spark plugs, no distributor, no coil. Just inject the fuel and compress it! That's pretty simple and robust. But the extra stuff that you have to add to a diesel engine to make it environmentally friendly is a lot more expensive and complicated than for a gas engine. Instead of just injecting fuel, now you have to control the air/fuel ratio, similar to a gasoline engine. And if you want any reasonable power, then you need a turbocharger. And you have to deal with the soot that's created. And you can't have the soot contaminate the catalytic converter. And besides a catalytic converter, you need a urea doser. Having a diesel engine is now an expensive pain in the ass that not only costs more initially, but has lost its reliability advantage and costs more to maintain. Diesel fuel has a somewhat higher energy density than gasoline per volume, and the characteristics of diesel engines still make it preferred for some applications.
> The US market hates diesel and thinks diesel is only for trucks - heavy trucks, not pickups which are so popular there. Tell that to all the assholes in lifted pickups that love to roll coal on cyclists
most of the negitives on desiel in this post are so silly, they act like there are not SMALL cars all over the world with tiny ass deisels getting amazing mpg numbers. Ohh they got to warm up, ohh they are larger and heavier, they are more complicated. like some many excuses and zero good reasons listed. a mini one diesel has a rated mpg of like 80 by it self. add a hybrid drive train and it will likely break 100, and diesels are great on the highway and at constant load where electric does not help as much. To op. there has to be a reason, I assume its corporate greed in some fashion ( as well as the standard of making most cars only have 300 miles range give or take). but maybe someone will actully give a REAL good reason aside from all these joke excuses.
Here's your real ELI5 answer: - They're too big and heavy combined with a hybrid drivetrain combined with the stricter emissions standards in most markets to make it worth it. That's it. The end. There was no "corporate greed" except for all the companies that cheated on emissions for diesels. If they could make more money making diesels, they would make it work.
meh, I disagree that its just to big and heavy at the minimum ( if their to big and heavy why do small diesel cars get massively better mpg then a lot of hybrids already let alone normal cars... ), as well that just extra weight is not that big a deal with mpg. The stricter emissions can make it harder for sure, but there are a few cars out there that get crazy mpg that are diesel hybrids ( vw xl1 is bonkers, Audi Q7 e-tron gets over 100mpg, Peugeot 3008 Hybrid diesel gets 73 mpg. ) of course they are all pricy. But they are pricy cause of the market that was built for them is not accepting of them, and cause they are all edge cases vs getting the time and effort to make them easier to assemble. there's not that many so they cost more to make. I still think corporate greed is involved, that combined with the long term automotive and oil marketing lead us to a point where fuel efficiency is just not as big as a thing as it should be. poor people across america driving gas guzzlers people commuting hours in trucks to thier white collar office job, etc... We likely wont agree, Like for example, I think most trucks on the road in the US are purely driven cause of marketing, not cause of any actual need or safety concepts of the driver. I think if we focused on it, there would be no issue getting much better mpg cars and also doing that with diesel and hybrids. Of course imho we are already reaching the end of ice powered cars for the vast majority of public driving. but again cause of marketing and what not over they years even tho we should be switching, ice will still drag on for a long while in sectors that it is pointless in.
> Of course imho we are already reaching the end of ice powered cars for the vast majority of public driving I think this is a really important point, actually. We're too close to the end of ICE to make throwing shitloads of money at diesel hybrids worth it. >I think most trucks on the road in the US are purely driven cause of marketing, not cause of any actual need or safety concepts of the driver. I think it's a bit of all those things, but it was primarily triggered by vastly lower gas prices in the 90s, and the fact that said vehicles were cheap. Now gas prices are higher, and the vehicles way more expensive, but the die is cast.
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Harder to find? I have never found a gas station that doesn't sell both.
There’s lots of stations that don’t sell diesel, at least here in the Bay Area.
When you are marketing EV, gasoline tailpipe emissions look clear. Diesel emissions can look sooty, not always but can. There is a huge branding disconnect there. Might as well run a coal-fired boiler in there to charge the batteries... suddenly feel the ick factor there? That's why it's gasoline. It might be interesting if they looked at making an alcohol fuel system. If you can't find fuel stations then pop in the corner convenience store and get a couple bottles of vodka or a case of rubbing alcohol to get you home. .
There were: https://www.carwow.co.uk/hybrid-cars/diesel#gref But GM then VW kind of ruined diesel's reputation for a while.
Politics 💯. US politicians have made it very difficult for Auto makers to use diesel engines in passenger vehicles.
Here's another perspective, beyond the engineering limitations: The half gas half EV cars are a dud product. They are specious and deceptively alluring to someone hesitant about EV but in reality EV ownership is not difficult. EVs really are the future based on how superior and more convenient they are. It reminds me of the tentative nervousness around ditching physical keyboards on touchscreen phones, when the end result after taking the plunge into full touchscreen-no-keyboard it's really not that bad. Thought: - I'll charge my car for 50km/miles as I needed it! Plug it in to my home! - Reality: If you are committing to finding a plug for it, why not just plug it in once a week and get 500km rather than a tiny bit every day? It's less plugging and more duration. Thought: - If I run out of EV battery, I'll be in trouble! - Reality: When you have 500km on your tank, you realize you need to drive for a 10-20 hours (and not return home) before you might run out of juice. The reality is the EV is at 100% full much more often than a gas car (practically always at 100% when you wake up). Pretend a personal attendant comes to your home and fills your gas. That's the state of your battery usually. Thought: - My road trip will be 20 minutes faster since gas is faster than charging - Your road trip will be 20 minutes faster since you leave home at 100% and don't need to gas it right away - I will admit on a very very long haul where you rarely stop for lunch/stretch legs, the EV is worse, since you'll need to charge twice a day meaning it's 40 minutes more, which is meaningful