why no prius diesel hybrid?!

[arnoutterschure]

why are/will there be no diesel-hybrid prius?

1) diesel is standard 20-40% more efficient than gasoline
2) today's ultra clean diesel engines emit less (particles, CO2, NOx, other air pollutants) than gasoline engines
3) Diesel engines last longer than gasoline engines: less wear and tear due to for example lower RPMs and lower operating temperatures
4) Provide more torque and power compared to gasoline
5) Hybrid diesels combine all of the above with the good of the hybrid, e.g. Peugeot (another great European brand that was bought-out by america's BIG 3) will launch the diesel-powered 2010 Peugeot 308 Hybrid HDi, featuring an outstanding fuel economy of 83 mpg on the combined cycle and emitting only 90g/km of CO2. This is nothing compared to Toyota Prius Touring Edition with its 55 mpg on the same combined cycle and 104g/km of carbon dioxide: 2010 Peugeot 308 Hybrid HDi easily trumps Toyota Prius « Auto Review.

ps: I rented a 2.0 TDI VW touran (compact MPV, like the mazda5) last year and it did 5L/100km (~45mpg) on average, including doing 85mph on the german autobahn for some time...

[chrisspaulding]

I agree. And don't forget, runs on filtered fast food grease too!

[Gadgetdad]

Except for the weight and the noise, and the temperature requirements I think a hybrid diesel makes sense.

In '79 I bought a VW Rabbit Diesel 4 speed stick, waited in line to buy one because of the worse oil problem then (tripling of price, shortages, rationing, odd/even fill up days). My MPG was in the 45-55 range freeway and overall around 40. I got better than the EPA estimates!

VW did a stupid thing in 1980 when they started making them in the U.S. The quality went way down and ruined consumer satisfaction. My Wolfsberg edition was great, but my friends '80 was riddled with problems including vibrations so severe the steering wheel came off while I was driving his car on the freeway

I loved mine though and wish I still had it!

[jdenenberg]

Originally Posted by arnoutterschure

why are/will there be no diesel-hybrid prius?

1) diesel is standard 20-40% more efficient than gasoline

Nonsense, diesel fuel has a higher carbon content and therefore 30% higher energy content/gallon. It also ends to be more expensive in the US so the miles per dollar is the issue, not miles per gallon.

2) today's ultra clean diesel engines emit less (particles, CO2, NOx, other air pollutants) than gasoline engines,

Not true, They emit more co2 per mile and more NOX. The Prius (and some other cars) have a PZEV rating. There is no diesel with this clean an exhaust.

3) Diesel engines last longer than gasoline engines: less wear and tear due to for example lower RPMs and lower operating temperatures.

True, but not in stop/start mode as in a full hybrid.

4) Provide more torque and power compared to gasoline

Again true but the more torque at low RPM is not required in a hybrid as the electric motors have tons of torque.

5) Hybrid diesels combine all of the above with the good of the hybrid, e.g. Peugeot (another great European brand that was bought-out by america's BIG 3) will launch the diesel-powered 2010 Peugeot 308 Hybrid HDi, featuring an outstanding fuel economy of 83 mpg on the combined cycle and emitting only 90g/km of CO2. This is nothing compared to Toyota Prius Touring Edition with its 55 mpg on the same combined cycle and 104g/km of carbon dioxide: 2010 Peugeot 308 Hybrid HDi easily trumps Toyota Prius « Auto Review.

ps: I rented a 2.0 TDI VW touran (compact MPV, like the mazda5) last year and it did 5L/100km (~45mpg) on average, including doing 85mph on the german autobahn for some time...

The best use of a diesel engine in a hybrid would be in a series hybrid (like the Volt) where the ICE just drives a generator so that the battery capacity is not the range limitation.

Jeffd

[kevinwhite]

Originally Posted by arnoutterschure

why are/will there be no diesel-hybrid prius?

<...>
2) today's ultra clean diesel engines emit less (particles, CO2, NOx, other air pollutants) than gasoline engines
<...>
4) Provide more torque and power compared to gasoline
<...>

(2) Not true - currently there are no diesel cars sold in CA because they don't meet the emission standards. There will be MY 2009 cars sold but even then they are dirtier than the best gasoline cars, and there is controversy over the impact of the very fine particulates that they do produce but will be allowed.

(4) Not true - in general a diesel of the same technology level will generate less power and torque than an equivalent gasoline engine:

For example the figures for the 2006 VW Jetta are:

Gasoline(turbo charged): 200HP @ 5500RPM, 207ft-lb @ 1800RPM
Diesel (turbo-charged): 100HP @ 4000RPM, 177ft-lb @ 1800RPM

A gasoline engine can run faster and so its power peak will be at a higher speed. In part this is because the rotating parts of a diesel engine have to be made more stronger and heavier in a diesel engine. Often the peak torque of a diesel will be at a lower speed than a gasoline engine - this may give the impression of more torque as often a gasoline engine will tend to stall at low RPM (my BMW 328 was an example of this although a fine engine in all other respects).

Although I would like for someone to produce a diesel hybrid other items to consider are that diesel costs 10-20% more (in the US) and that the refinery can get up to twice as much gasoline from crude oil compared to diesel.

kevin

[arnoutterschure]

sorry for some of my slip ups, like on NOx emissions, and fuel efficiency (should be ~30% on average) but; diesel fuel indeed contains more carbon than gasoline so it releases more CO2 per gallon burned. Nevertheless, the diesel engine's greater fuel efficiency means considerably less CO2 is released per mile driven compared to a similar-sized gasoline engine.

Typically, gas engines make more horsepower, while diesels produce more torque. By design, gas engines rev faster and are able to reach higher rpm peaks than diesels. This allows them to attain greater horsepower numbers and quicker 0-60-mph times. However, because of the relatively high-compression ratio necessary to ignite the diesel fuel (17:1 diesel versus 9:1 gas), a diesel makes all its torque and power in the low rev range.

As an example, the GM 8.1L gasoline V-8 puts out 340 hp and 455 lb-ft of torque, while GM's 6.6L V-8 turbodiesel puts out 300 hp, and 520 lb-ft of torque...

In addition, I did some further digging and found that making a gallon of diesel fuel requires 25% more oil (not 200%...) and emits 17% more heat-trapping greenhouse gases than gasoline (reformulated with MTBE...). Similarly, diesel requires 17% more oil and emits 18% more heat-trapping gases than gasoline reformulated with ethanol. This means that diesel fuel's advantages from its higher per-gallon energy content and better performance on greenhouse gases are partially offset by the impact of diesel's fuel-production process.

Brings me to the next diesel issue: Synthetic Ultra-Clean Diesel from Coal to Liquid or Natural Gas to Liquid or Biomass to Liquid production. How would that compare?

[kevinwhite]

Originally Posted by arnoutterschure

s<...>

Typically, gas engines make more horsepower, while diesels produce more torque. By design, gas engines rev faster and are able to reach higher rpm peaks than diesels. This allows them to attain greater horsepower numbers and quicker 0-60-mph times. However, because of the relatively high-compression ratio necessary to ignite the diesel fuel (17:1 diesel versus 9:1 gas), a diesel makes all its torque and power in the low rev range.

As an example, the GM 8.1L gasoline V-8 puts out 340 hp and 455 lb-ft of torque, while GM's 6.6L V-8 turbodiesel puts out 300 hp, and 520 lb-ft of torque...

<...>

You are comparing apples to oranges - for the same size engine and similar technology a gasoline engine will produce more torque - you are comparing a naturally aspirated gasoline engine with a turbo-charged diesel. If you put a turbo-charger on the gasoline engine you could probably get more torque than the diesel.

A diesel engine limited in how much you fuel you can inject before smoke appears in the exhaust due to incomplete combustion (the smoke limit) - a gasoline engine can get to a stoichiometric mixture or richer without this happening.

These are also much larger engines than will be used in a hybrid Prius!

My example of a VW Jetta is much more appropriate.

kevin

[brighamwj]

Originally Posted by jdenenberg

Nonsense, diesel fuel has a higher carbon content and therefore 30% higher energy content/gallon. It also ends to be more expensive in the US so the miles per dollar is the issue, not miles per gallon.Not true, They emit more co2 per mile and more NOX. The Prius (and some other cars) have a PZEV rating. There is no diesel with this clean an exhaust.True, but not in stop/start mode as in a full hybrid.Again true but the more torque at low RPM is not required in a hybrid as the electric motors have tons of torque.The best use of a diesel engine in a hybrid would be in a series hybrid (like the Volt) where the ICE just drives a generator so that the battery capacity is not the range limitation.

Jeffd

All of your points are right on. However, there would be an obvious demand. The bigest issue would be the exhaust - scrubbers in the manifold?
The increased efficiency might offset the costs. But how would you constantly stop and start the glow plug based diesel thumper and how efficient would a tiny diesel (smaller than the Rabbit diesel) be mated with an electric motor?
Anyways, we need annual carbon taxes per vehicle to be paid with registration. i.e Charger SRT 8 = big tax, PZEV vehicle = small tax. Sorry that is a whole new thread.

[Stefx]

One note... diesels have a narrower range of operational rpm compared to gas engines... it wouldn't work with the current MG1/MG2/ICE integrated CVT system. A hydrid diesel would probably need a separate transmission.

[dbcassidy]

A diesel / electric combo (think locomtives) would give you instant torque and real good mileage. The emissions would have to meet the new standard coming out in 2010.

Also, how many of us would be willing to pay more for the diesel option as well as more $$$ / gallon of diesel?

Dbcassidy