Why aren't hybrids diesel rather than petrol?
Hi, this has been bothering me since i saw my first honda insight in about 2006, and pops up whenever i think about a Prius - why isn't the conventional engine a lovely efficient diesel rather than a regular petrol?!
For maximum mpg, surely harnessing free electric to the already more economical diesel is best? Weren't submarines always diesel (not petrol) electric, so there can't be some massive problem with using diesel? Apologies if this subject has already been raised and answered elsewhere, but it is still a huge puzzle to me! Yes, there's a couple of 4x4 diesel hybrids, but I'm talking normal cars here! |
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I've often wondered this myself, they are usually mated to a rather inefficient petrol engine, almost counterproductive as if one cancels the other out!
The reasons I can think of are: Diesels take up more room, dpf's, turbos and intercoolers etc which also makes them heavy, again not a great combo when you're trying to improve economy. There quite a few diesel hybrids available, they're just not marketed very well as a regular diesel offers similar economy. Peugeot, Citroën, Volvo, Audi, BMW etc all have diesel hybrids. They make far more sense to me, diesel on the highway to reduce fuel consumption and electric in built up areas to slash emissions. |
By the way, the French hybrids are actually really nice looking cars!
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Yes, they are - and i've never heard of them! I often feel i betrayed Citroën when i bought my Hyundai new, as their second hand old diesels had beaten their manufacturers mpg claims - unlike today!
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Oh, and its back to unit conversion disaster...i changed our Honda CRV from USgallons to litres, then entered the 30.1 litres i used to travel 380 miles and acheive 44.25 mpg. 57 mpg appeared on my dashboard....i ve had to temporarily stick a fake 39 litres on the fill up to show 44.3 mpg. I ll sort it out later!
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The tl;dr for why there is few diesel hybrids.
A diesel would add to the final price for what may not be as large of a gain in fuel economy. Hybrids aren't just fuel efficient, but low emission. Making a diesel one as clean further adds to the cost. The two biggest markets for hybrids, Japan and the US, favor gasoline. Locomotives and some ships are serial diesel electric hybrids, but are so for reasons besides efficiency. Directly driving the wheels on a locomotive with a diesel would require a large, complicated transmission. If such a beast could physically fit on the locomotive, it wouldn't have been an improvement over the steam engines still in use up to the '60s. I don't know if a diesel electric was more fuel efficient, but their design simplicity made them for cost efficient over a steam locomotive in terms of crew and maintenance. For ships, a diesel-electric system meant that the engine didn't have to be in the aft and inline with the propellers. It could be positioned midship for better weight distribution. Electric motors also allowed for steerable propellers in place of a rudder. Some can spin 360. So the ship becomes more agile, comparatively. Subs had batteries so they can dive, and the electric only propulsion is quieter than nuclear. The conversion losses of serial hybrids make them unattractive for a car. The Accord hybrid is the closest to a serial hybrid available, and it still directly connects the ICE to the wheels on the highway. The i3 REX is a serial hybrid, but is a plugin first. With 70 miles of grid powered range, the efficiency losses of a serial hybrid become less important. In general, the efficiency of a plugin's range extender becomes less important the longer the grid EV range is. You need to keep in mind that the current hybrids originally were develop not to just reduce fuel use, but also emissions, and not just the carbon one. In Japan, the government, through MITI, ran several LEV(low emission vehicle) programs to R&D reducing car pollution in cities. These go back to at least the '80s. They experimented with EVs, hybrids, and FCVs. Without the LEV programs, the Prius likely wouldn't have come to market. The US had the Partnership for the Next Generation of Vehicle. The concept cars produced by the big three were diesel electrics, but they were never required offer anything for sale. So with the diesel engine, hybrid system, and light weight components, production versions would simply have been too expensive. ford did start work on their Escape hybrid during this program, and a government research was perfecting a hydraulic hybrid. The hybrid premium discussion has dogged hybrids since they arrived. A diesel premium would just make it worse. More so now that diesel costs more in the US. That diesel premium will be higher getting it as clean as the gasoline. The gasoline engine in most is quiet efficient. The are Atkinsonized for greater fuel efficiency. They lose power, but got enough for steady state cruising, and have the electric motor for low speeds and accelerations. The 4th gen Prius ICE will have a thermal efficiency real close to a diesels. Then the gas ICE and electric motor have better synergy. ICE, high end power; motor, low power. A diesel's power band overlaps more with the motor's; limiting how much advantage came be taken of both in the system. So a lower gain than expected. Not that a diesel hybrid can't be done, but one of the most successful ones, the Volvo XC60 PHV, to date, is a luxury brand and a plugin. The extra cost of the diesel over a gasoline engine is a smaller fraction of the car's overall price. A non-plugin diesel hybrid should do well in Europe though. As long as the political climate doesn't move against diesels in general. |
Well I was surprised to see that the UK actually buys more plug ins than any other country in the World. There were actually 52,000 alternative fuel vehicles registered last year, and an incredible 68% people buy cars with carbon emissions of less than 100 grams per KM, about the same a Prius.
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Diesels can also be very hard to start in cold weather. Diesel engines themselves use much stronger components to handle the higher compression/detonation and thus cost more to manufacture. Diesels in America also have an unjustly earned reputation for being un eco friendly, which is exactly the opposite of the market they are trying to attract with hybrids. Most people who love hybrids equally hate diesels here, mostly because many rednecks here boost up the horsepower on their giant diesel trucks and they billow out lots of soot when they are racing around.
https://badges.fuelly.com/images/smallsig-us/319192.png |
The trend in Europe seems to be to skip over hybrids and go right to plugins. I think it has much to do with avoiding taxes and city congestion charges.
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Yes that's true, and the fact that the UK already has hundreds of free charge points all over the place. And yes, I did say free. Although wireless instant induction charging as per electric toothbrushes etc is just around the corner, so all these hybrids with wires hanging out will soon be outdated.
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Induction and other wireless charging will have more charge losses than the wire though. In addition to costing more.
Which is fine for a toothbrush or even a phone, but becomes quite measurable in the case of cars. |
But it's likely to be the way charging cars is going, as it is at the minute, my nearest charge point is beyond reach of an Ev. A lot of people here don't even have a dedicated car parking space, nevermind a driveway/garage to make charging easy, so wireless/induction charging would be more convenient for more people and broaden the market a bit.
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Perhaps once a standard is settled on, and someone is found willing to pay it.
Based on announced partnerships, Toyota is going with magnetic resonance. |
Hi folks,
In the UK the Outlander PHEV is selling really well. I just got one.I think the 2 big issues with diesel in hybrids are cost and weight. Also in Europe we are now being told that diesels are evil. That's after 20 years of being told we should all be driving diesel cars as they are better for the environment. Cities such as are Paris are now considering banning them. It just goes to show that you cant believe what your government tells you! |
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I suppose it would be more accurate to say that the only reason diesels are popular any place involves fuel cost. Diesels are heavier and until recently noisier than gasoline engines for the same power output. Their advantage is that they burn less fuel, leading to lower costs unless Government gets involved with fuel tax. Whether you like it or not, whether you believe it or not, COST is the driver. Read your own posts about how much money you were going to save when you traded your Abarth for a Clio.
The aviation press is making a big deal about the first ever successful flight of a diesel-powered helicopter, and the only reason anyone is bothering is Government policies basically making aviation gasoline very expensive and in some places unavailable. The reason helicopters have not flown with diesel power in the past - too heavy for the power. That is the same reason airplanes and motorcycles do not use diesels. By the way, I have owned only one diesel, a somewhat less than wonderful Renault. I have driven many, some military, some civilian, and only yesterday drove one professionally. My experience with the Renault turbodiesel, particularly in cold weather, tells me the putative savings with a diesel are not worth the trouble. |
Even the turbine powered helicopters are gasoline?
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I should have been a little more clear in my post. Reciprocating engines - piston engines - in aircraft are used in the lower power regions, up to perhaps 300 horsepower per engine. They are gasoline engines because diesels are too heavy. Above that, turbines become "better." Turbines typically have much better power to weight ratios, but are also more expensive and less efficient. Turbines lose efficiency very rapidly at less than full power, but of course aircraft - especially helicopters - tend to operate at high power settings most of the time. |
That's my point Charon, you seem to be basing all these negative opinions about diesels on one bad experience you had with one vehicle some 3 decades ago. People aren't forced to drive them, they chose to, they dominate most of the car market from small family hatchbacks, to expensive premium brands at the top end. If they were expensive to maintain and unreliable, do you think they would outsell petrol by 4 to 1? Yes fuel cost is one of the many factors, but it's not the only one.
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Percentage sales of diesel cars is a little over 50% in Europe and a bit less in the UK. Europe is by far the biggest market for diesel. Petrol is much cheaper in the US as far as I know, and that's one of the reasons that diesel vehicles have never had a big market share there. They cost more to make and therefore buy, and with cheaper fuel the saving will never cover the increased purchase cost.
I've owned 7 diesel cars over the last 20 years. Some had great engines and were lovely to drive. There is always more noise and vibration though, no matter how expensive. All these were big cars, which is where you get the greatest benefit in terms of economy. They are definitely not hard to start when its cold, although they may have been 40 years ago! But you don't have to do much research to see that they are now considered by European governments to be very damaging to health. They will probably go back to being mostly seen in large vehicles, with smaller cars likely to be using small petrol turbo engines which can give similar economy to diesel. Volkswagen for example have said they will no longer make any diesel engine smaller than 1.6 ltr. |
I have driven diesels for over 20 years and seen them really improve.
My Bmw around town gets 46/49 mpg and just over 60 mpg on the motorway. But DPF's has made me now return to petrol as I only do 20 miles a day now. All I can say is roll on hydrogen cars. |
As diesels become more advanced, reliability improves all the time. If you go to the old French colonies in Africa, you'll find Classic Peugeot diesels with over 1,000,000 Km on them, still going strong. And remember those cars have spent most of their life driving in desert Sands off road.
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They don't make Peugeots like that any more!
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My Renault diesel never left me stranded on the road, although an alternator failure did. It was a chronic oil leaker, and even after spending hundreds of dollars I couldn't cure it. It utterly refused to start in temperatures below 20 F, unless I put an oil pan heater on it. And yes, that was after maintenance work at Winnebago. Yes, it had glow plugs; yes it had dual batteries. Its power steering rack-and-pinion failed; its starter failed; its alternator failed; its clutch slave cylinder failed; some of the plastic isolators on the sway bars failed; its injector pump leaked (not its fault because the US switched to a low sulfur fuel and the O-rings dried out); and there was no doubt more I can't remember. Its "house" battery was damn near impossible to access, although the automotive battery was conventional. I knew Renault's reputation for "reliability" when I bought it, and damn near didn't buy it because of that. But I hoped having Winnebago's name would help. It didn't. All these failures in less than 80,000 miles.
It also had an interesting failure in the hydraulically-activated clutch. When it had a long hard pull, say up a long hill, the clutch would "go away." Pressing the clutch pedal resulted in no clutch release at all. The clutch did not slip - it wouldn't release. My conjecture was that the slave cylinder was too near the exhaust pipe, and the heat from a long pull vaporized the fluid. I insulated the exhaust pipe and installed a shield. It helped, but did not cure the problem. Fortunately I know how to shift without a clutch. Unfortunately, it always happened on an uphill pull, so when the engine "fell off" the turbo due to low revs, there was one chance only to make the downshift and "catch" the next lower gear with enough engine revs to get the turbo to spool up. The downshift could not be made without the turbo "unspooling" because the reduction in throttle necessary to break torque killed the turbo anyway. Bear in mind that when going uphill speed drops off quickly due to gravity. Our school district has five buses. Two are gasoline; three diesel. The gas engines start in any weather without any sort of engine heater and with no difficulty. The diesels will have their block heaters plugged in pretty much whenever the weather is projected to go below freezing. Even then the "wait to start" lights take a while to go out. It has happened that the block heaters were forgotten. In one case the driver unloaded in front of the school and left the bus there instead of parking it where the cords are. It took hours to get the thing started and moved. Many farmers around here use diesel tractors, and usually have block heaters on them. Many of those same farmers keep an old gas tractor for a winter time "chore" tractor. If they have to get out a diesel, they use the gas tractor to drag the diesel around the farmyard until they get it to light off. Yes, I do have some experience with diesels. Yes, once started diesels are usually pretty reliable. No, I do not intend to buy one for personal use. |
Well you are entitled to your opinion of course, all be it from 1984...By the sounds of things, you have experienced commercial diesels, but haven't really owned an every day diesel car. French cars are now just behind Japanese when it comes to reliability now, with Renault in the top 10, you remember when Skoda used to be the laughing stock of the motoring World? Well now they rank in the top 3, usually first. As we try and explain every day almost, things have advanced at an astonishing rate, engines become faster, more reliable, more technical and yet cleaner and more efficient every year. How many times have Audi won the 24 hour let Mans race in their diesel powered race car again?
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Charon, pop down to your local dealer and ask to drive a fast diesel, you'll see what all the fuss is about. Some of these cars do 0-60 in less than 5 seconds and some are rated at 60 UK MPG, not exactly tractors like! ;)
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The diesels i have owned started in the late '80s and up to 2000. I generally paid £500 for them, and they would be 12-15 years old at time of ownership. I would keep them for 1-2 years (usually to their graves!).
I owned 2 nissan bluebirds, 2 peugeot 406s, 2 citroen ZXs, a xantia, a vauxhall astra, a polo and a rover 75. Though i had an eye on the mpg, i was a high level pizza delivery boy(!), so was blasting these bangers round urban circuits, speedbumps galore, as fast as i could. Apart from that rover, none of them cost more than £500 a year in repairs. None let me down or would nt start (including winters with 6 and 4 weeks of snow). I ran most of them on heating oil, at 1/3 the cost of diesel at the pumps! So for me, (apart from the rover!), diesels were cheap and reliable - cheap to purchase, maintain and run. I seriously was the top driver for both my local domino's and several other take aways, and you only got there by being quick, so my old diesels were hammered, hence they were mainly sold to a scrapyard after i d finished with them! |
My present primary vehicle is a 2012 Toyota Tundra with the 5.7 V-8 and six-speed automatic. I expect it to be the last vehicle I'll have to buy. It cost me considerably less than any of the modern diesels available here, and is a whole lot more versatile. Those of us who sometimes have uses for pickups have difficulty imagining life without one. I have already looked at the option of acquiring another more economical vehicle for those times when the pickup is overkill, but the economics of taxes and insurance make them non cost effective.
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Most of those diesels listed above came with a 2 litre 4 cylinder engine, anr less than 100 horse power. Tax for the year is around £200 (it is zero on my current ride!). 4 of them were estates and 4 were hatchbacks, so though not as versatile load carriers as pick ups, they had the choice of 5-7 occupants, or perhaps a sofa, bed, wardrobe or selection of kids gokarts and electric jeeps!
They would give be over 50mpg, the equivalent petrol versions 30 mpg for the same type of routes. Petrol is slightly cheaper, but only by about 5%, and road tax the same. My first diesel car was forced upon me - when i replaced it with the same model, but the 2 litre diesel replaced by a 1.6 petrol, i watched my fuel bill double! I sold it immediately and have owned only diesels since, that was 2003. |
They were all 5 speed manuals too.
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When i see all the hard work, mods and hypermiling techniques people are using to get a 30mpg petrol car up to 40 mpg, i always think how much more benefit there would be if the starting car was already a 50 mpg diesel!
I am starting to understand the anti diesel sentiment in the US, luckily in the UK diesels are excellent, and high demand will continue innovation from manufacturers. |
I believe the future is with full electric and my favorite, plug in hybrids. The range on plug in hybrids is going up every year, there cost to run is very cheap, and they have a small gas engine for long trips or when you can't charge them. Supposedly about 1/4 the cost of a gas engine to drive around.
BTW I believe diesels are very inefficient when cold, but take very little fuel at idle when fully warmed up, they may not do so well on mpg when constantly started and stopped as a hybrid. https://badges.fuelly.com/images/sig-us/319192.png |
I agree plug in is the way forward, but doubt they ll be truly affordable and practical for a long while yet. I had one diesel citroen that was stopped and started 50 times a night driving urban pizza delivery and still giving me 55 mpg at the pumps!
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Plug ins are only popular in certain regions, urban areas where people can charge them, or people who travel alot on motorways where they can stop at service stations to charge them. If you live rural, like alot of Britains do, then you can't even make it to your nearest charge point. They make sense in London, they can save up to £3000 that's $4500 a year in congestion charge, a daily payment you need to make just to enter London city centre. I do still believe though that induction/wireless charging will make plug ins more appealing in the next few years.
Hybrids are OK as a concept, but I find having an extra motor, batteries and all the hardware that comes with it, a bit counterproductive. That's why I'm interested in the compressed air hybrids coming soon. One gas engine, two fuel tanks, one carries petrol, the other carries compressed air, filled by the momentum of the car when coasting and braking. Air is free and unlimited and is emission free, this concept excites me! |
Never heard of that compressed air, sounds very exciting! Maybe i need to keep my finger on the pulse more...
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The idea is to charge your hybrid at home. The uk overnment give a grant to install a dedicated charger at your home, although you don't have to have one, you can charge from any power socket.
If you don't have off road parking its not for you, but many people can do their daily commute without using any petrol at all. Its not where you live that matters, its the type of trips you take that make it worthwhile or not |
What sort of range does a fully charged light phev get from an overnight charge?
Would hills reduce it drastically? |
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