Why are most hybrids based on gasoline engines? 1

[SomptingGuy]

Why is it that car companies are pitching gasoline-based hybrids as alternatives to diesel vehicles? Surely a diesel-hybrid has a similar advantage over a gasoline-hybrid as a diesel has over a gasoline?

Sure you can downsize your gasoline engine and run it more efficiently - possibly even without a throttle. But even then it's still going to be less efficient than a diesel as the main power source in a hybrid.

Or is it simply image? Hybrid=high-tech, Diesel=low-tech. Ergo, hybrids cannot use Diesel engines.

 

[GregLocock]

I am told that Toyota's intention was to make the hybrid as car-like as possible. Since diesels have a lousy rep in the USA, I guess that pushed them towards gasoline. Do Honda even make a diesel?

I agree, a diesel hybrid would be a much better idea, how do they handle being started and stopped repeatedly? I can imagine there would be emissions problems.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[SomptingGuy]

My view is obvious from the wording of my question and concurs with Greg's "lousy rep in the USA" statement. If ultimate MPG is the goal, I would say that diesel-hybrid sounds good. If high MPG without stooping to Diesel is the goal, gasoline-hybrid.

I'm not 100% sure about the emissions issues, but stop-starting a diesel is pretty simple, because of the fact that the diesel will be DI rather than port-injected, so there are no "bad" cycles.

 

[TheBlacksmith]

Diesel fuel is smelly. Diesels are noisy. Diesels are smelly. Diesels smoke. Diesels are hard to start in cold weather. GM rushed a diesel to market in the 70's oil crises. Oil companies rushed diesel fuel to the market without regard for cleanliness or temperature (#1 or #2) in the 70's. Today the big 3 all command about a $5000 premium for diesel power in a 3/4 ton pickup, which at roughly the same price per gallon and maybe 25% better MPG, will not be recouped by the original owner. True or not, these all contribute to a public perception that makes diesels barely acceptable.

 

[amorrison]

Diesel gives less HP per pound therefore less performance.

 

[NickE]

amorrison4 -- HUH? I had always thought that diesel has a higher energy density than gasoline. I thought the scale went like this:

Ethanol<Gasoline<DieselFuel

 

[MikeHalloran]

I suspect he meant to say Diesels give less HP per pound _of_engine_.

Given the extra weight of batteries in a hybrid, the rest of the powertrain has to go on a diet to keep the vehicle weight anywhere near acceptable.



Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA

 

[NickE]

ahhh... well that would be a problem, since making high efficiency diesels with aluminium blocks and heads might be kind of tricky.

I think that if I were going to make a ICE/electric hybrid I would try to use something completely new.

What is the best method to turn gasoline/diesel fuel into rotational energy to spin an alternator? thermodynamically speaking. This ICE would also have to be quick starting an stopping, while not suffering large efficiency losses and emissions problems. there should be an optimization of the differing goals.

This might of course just leave us with the answer that was given about most efficient ICE: It depends.

IE: Turbocompounded diesels won that discussion with apprx 50% thermal efficieny. But in this case the power to weight ratio is not very high. While turbines might be relatively light weight, they probably dont like to start and stop all the time, and have their torque peak at stall.

 

[MikeHalloran]

The problem with using 'something completely new' as a component of a complex product is that you have to develop the _component_ before you can develop the product.

Markets don't wait for compounded development cycles.





Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA

 

[drwebb]

Is this the Japanese OEMs 'pitching' or US? (I haven't noted mention of diesels in the marketing efforts myself) If the Japanese then they don't do much with diesels in the US so maybe can expand their vehicle portfolio. If the US then their reported strategy is to apply hybrid technologies to improve the mpg of their trucks/SUVs where non-hybrid diesels would be an alternative.

The Blacksmith has pointed out the purchase price premium of diesel vehicles, so from a marketing perspective a US consumer willing to pay extra for the different technology of a hybrid (i.e. Prius, Civic, soon Accord) might also be considering a diesel (Golf, Jetta, Passat).

 

[curious125]

Would you not be able to use a noteably smaller diesel engine versus it's gasoline equivalent? That alone should almost even the plain for the diesels "lower" HP to weight ration to the gasoline engine. Wouldn't it?

Most new TDI diesels don't make any more noise than a conventional gasoline engine in the low to mid RPM range.
After all it's not for racing purposes.

 

[SomptingGuy]

drweb:

I guess it's both.

Japanese OEM's have never really been that big on Diesels in the passenger car market. And they do excel in small, efficient gasoline engines, which are ideal for hybrids.

And I keep reading in the automotive engineering press that the advent of the hybrid in the US will kill off any future for diesels in that market.

Does diesel really command a $5000 premium over gasoline in the US? That's amazing - the difference is nothing like that in Europe for passenger cars (<$1000 difference generally).

 

[TheBlacksmith]

SomptingGuy-
Go to any of the big three's auto web sites and click on the build your own - first you must select a 3/4 ton pickup; F250SD, Ram 2500 or C/K 2500, which in itself costs more then the 1/2 ton pickups, then check the retail cost for the diesel option, it is right at or over $5,000. BTW, I work with big diesels and if the price difference was like Europe, I've have a diesel pickup, but I can buy a lot of gas for my 4.6 Triton for $5,000.

 

[SomptingGuy]

TheBlacksmith-

I forgot that you were probably refering to agricultural vehicles. The UK press often call them "Chelsea Tractors" here.

In the passenger car world, there aren't many diesels to choose from in the US. However, I did find that the list price of a Mercedes Benz E-class diesel is about $1000 more than the equivalent gasoline (E320 CDI - $51800, E350 - $50800). Not that different from Europe after all. I know which of the two I'd rather have.

 

[Paulista]

SomptingGuy has a good point there.

European car manufacturers are betting on the diesel.

There is a whole array of frugal consumption, low-noise, high-speed plus impeccable emission diesel engines that are being offered as alternatives to petrol-engines on a great deal of car models.

At the high-end of the market, Mercedes, Audi and BMW have introduced state-of-the-art diesel engines that are simply outstanding from any perspective.

 

[Azmio]

Here are the possible reasons why gasoline engines are preferred by Honda and Toyota: -

1) Hybrid is great for Japanese 10-15 cycle which has a lot of part throttle conditions. Therefore, it's suitable for Japanese market. Diesel powered cars on the other hand are not allowed to enter Tokyo city, it's a no no to have hybrid with diesel engine
2) diesel engine is not so good at high rpm. It is also heavy and requires bigger displacement for higher horsepwer. In this case, gasoline is favored for higher output and great for highway driving whereas electric motor will take care of the city driving

Honda has a 2.2 L TC diesel with Aluminum block. Good job by Honda considering it's their first diesel engine

 

[j2bprometheus]

Hi-
Here are the reasons for no diesel in the US for hybrids (in my opinion):

1. No low sulfur diesel fuel available in the US until 2006

2. US emissions regulations are written such that NOX emissions are heavily penalized compared to European regs. This makes meeting the US emissions regs a big development program for a diesel, especially when low sulfur diesel fuel is not available. Much easier to meet US emissions regs using a gasoline engine.

3. Toyota & Honda do not have much experience with diesels in passenger cars. European automobile manufacturers do have lots of diesel passenger car experience.

I would be pleased to see the Mercedes "bionic concept car" (diesel engine, not a hybrid) reach production. The claimed fuel economy for it is 84 MPG on the combined US test cycle.

j2bprometheus@aol.com

 

[TheBlacksmith]

SomptingGuy - I was referring to heavy duty pickup trucks (lorries?) and SUV's that people buy (1) to show off or (2) to pull 32 foot camping trailers or large show horse trailers uphill at speeds well inn excess of the posted limits. About one in ten are crawling through a construction zone or farm with a heavy load in the bed or on a trailer behind. Actually that seems to be the market in US today - about $50,000 - be it a loaded luxery US pickup truck or a Mercedes Sedan.

Blacksmith

 

[CCycle]

J2bprom.. Low sulfur diesel is in US now and has been for a year or more. It is giving us fits with the older engines. Bosh type injector pumps in particular do not want to run on it.
Your reason #2 is right on. They are doing all sorts of things like exhaust recirculation to lower NOx. This drops the efficiency advantage of the diesel.

The diesel took over large trucks because of its efficiency. It took over agriculture because of efficiency and the diesels pull better. But we have stumbled in getting them into light trucks and automotive. With present emission standards they probably will never supplant the computerized si catalyst engine in automotive.

Tell me, Why are we stuck on high molecular weight diesel fuel? It seems like the particulate level would be improved it we ran diesels on lighter fuel similar to a gasoline cut. Of course it would not be necessary or desirable to include additives and refining methods to increase octane. They would run on straight paraffins similar to the crude before modification.

 

[amorrison]

Diesel oil provides it's own lubrication in the injector/pump so wear in minimal.
A pump for none self lubricating "gasoline" to several thousand psi is probably not easy to design.