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Why are most hybrids based on gasoline engines?

Why are most hybrids based on gasoline engines?

Why are most hybrids based on gasoline engines?

(OP)
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.

RE: Why are most hybrids based on gasoline engines?

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.

RE: Why are most hybrids based on gasoline engines?

(OP)
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.

RE: Why are most hybrids based on gasoline engines?

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.

RE: Why are most hybrids based on gasoline engines?


Diesel gives less HP per pound therefore less performance.
 

RE: Why are most hybrids based on gasoline engines?

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

RE: Why are most hybrids based on gasoline engines?

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

RE: Why are most hybrids based on gasoline engines?

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.

RE: Why are most hybrids based on gasoline engines?

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

RE: Why are most hybrids based on gasoline engines?

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).

RE: Why are most hybrids based on gasoline engines?

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.

RE: Why are most hybrids based on gasoline engines?

(OP)
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).

RE: Why are most hybrids based on gasoline engines?

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.

RE: Why are most hybrids based on gasoline engines?

(OP)
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.

RE: Why are most hybrids based on gasoline engines?

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.

RE: Why are most hybrids based on gasoline engines?

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

RE: Why are most hybrids based on gasoline engines?

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

RE: Why are most hybrids based on gasoline engines?

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

RE: Why are most hybrids based on gasoline engines?

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.

RE: Why are most hybrids based on gasoline engines?


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.  

RE: Why are most hybrids based on gasoline engines?

For CCycle:

      Low sulfur diesel fuel is not yet widely available in the US.   

      Go down to the fuel station near where you work, take a small sample of diesel fuel & have it tested.  I'll bet that the test will indicate that the sulfur is high.
      
      Automakers want consistent fuel all across the US.  The EPA will not allow them to sell a vehicle that relies on low sulfur diesel fuel until low sulfur fuel is the only transportation fuel available in the US.
       

RE: Why are most hybrids based on gasoline engines?

Oops,   make that  "... only  DIESEL  transportation fuel..."

RE: Why are most hybrids based on gasoline engines?

Hi,

To my opinion there are several reasons to choose a gasoline engine in a hybrid car, but also some reasons can be found to choose Diesel!

Diesel cars develop a relative high torque, but a relative low amount of HP. In a hybrid car power is needed, because the torque is already supplied by the electric motor.

A turbo would solve this problem, but will only be effective a (relatively) high revs. A turbo doesn't like to start and stop continiously either.

Both Toyota (2.2 upto 175hp) and Honda (2.2) have excelent Diesel engines at the moment, so that will not be the reason to choose Gasoline.

The somewhat narrow view (to my opinion) of some people on Diesel engines is not completely correct. Carbon particle filters and catalic converters decrease the emision of modern Diesel powered cars enormously. Turbo charged Diesels have equal power, much more torque and a much better km/l (MPG) than Gasoline cars.
Ouside the US the development of the Diesel engine hasn't stopped....

Still the question remains... what is the best type of engine for a hybrid car..?

I'd choose (as Honda and Toyota did) a small gasoline engine with a high power (not torque) to weight ratio..

grtzz, Geert

RE: Why are most hybrids based on gasoline engines?

GM and others are making diesel hybrid busses.  Each one can save more fuel than 100 Prius.  I tried to talk my sister into buying a VW diesel instead of a Prius.  She said she didn't know anyplace to buy diesel near her house & didn't want to get the smelly stuff on her hands.  Besides, the Prius has that green high tech halo.

The main reason we don't have diesel hybrid cars at this point, IMHO, is that with the price premium of a hybrid already too high, a additional $1000 for the diesel puts it out of the question.  Add to that the weight, emmisions & public preception (in USA) and I'm sure the marketing guys went with the safer bet (again in USA).  Europeans actually prefer the diesels over the gas engines but their tax structure is heavily biased toward diesel so they have had decades of favorable experience.

RE: Why are most hybrids based on gasoline engines?

(OP)
Actually, the tax structure in the UK is biased against diesels.  As company cars they are taxed more.  And diesel costs more than gas these days.

RE: Why are most hybrids based on gasoline engines?

dgallup's sister may be onto something there.  In NJ where self-serve pumping is prohibited by law they seem to be selling quite a few TDIs.

RE: Why are most hybrids based on gasoline engines?

Im not too sure if this would affect the modern common rail diesel engines, but i imagine a diesel hybrid may have probs with engine temps being to low for efficient and clean running with continualy starting and stopping.

  I guess the ideal would be a diesel hybrid running on vegetable oils, no co2 probs......

Ken

RE: Why are most hybrids based on gasoline engines?

There are only a handful of production passenger cars on the market now (all gas) but many fleets of hybrid busses and prototype medium and heavy trucks (all Diesel).

It is probably a wash in terms of numbers of hybrid projects going on now. In terms of total number of vehicles in the hands of consumers, gas wins for now.

Best regards,

Matthew Ian Loew


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

RE: Why are most hybrids based on gasoline engines?

"Surely a diesel-hybrid has a similar advantage over a gasoline-hybrid as a diesel has over a gasoline?"

A gasoline engine is less expensive to produce than a diesel engine.  A hybrid drive train, with its electric motor and batteries, is already more expensive to produce than a conventinal drivetrain.  Adding the more expensive diesel engine option would make the hybrid cost prohibitive.

Of course, if one were to figure out a way to reduce the manufacturing cost of a recip diesel engine, then it becomes an economically feasible proposition.  I've been working hard on this.......

RE: Why are most hybrids based on gasoline engines?

Look at what San Diego State students developed over 6 years ago. It is a 1.2 liter diesel and a 200hp AC motor, with 28 sealed lead acid batteries. www.L3Research.com

RE: Why are most hybrids based on gasoline engines?

I think the question is not whether a diesel engine could work in a hybrid vehicle, but rather whether the electric hybrid system would add as much benefit to a diesel powered vehicle as it does to a gasoline powered vehicle.  

Gas engines develop maximum torque at high rpms, while electic motors have max torque at zero rpm.  Gas engines are also not very efficient at idle.  So, for stop and go driving, the electric motor complements a gas engine very well.

Diesel engines, on the other hand, develop maximum torque at much lower rpms compared to gas engines, and they are much more efficient at idle because they can run so much leaner.  Combine those two characteristics with the inherently more fuel efficient nature of compression ignition, and it becomes apparent that an electic motor would not give you the necessary gains in a diesel powered vehicle to justify the added cost and weight.

RE: Why are most hybrids based on gasoline engines?

I’m just the chemistry guy but get astonished to see how badly the rest of the world know modern Diesel engines produced here in Europe. Now we have an 1.2 liter 16v engine with 90bhp and 200Nm (constant within 1750 to 4000 rpm), produced by Fiat sold by GM on its Astra. The same engine can easily reach 110bhp. With the new biturbo technology it may well go to 120bhp(now it is VGT) without smoke...want smaller? 0,8 liter (Mercedes Smart), by the way, totally aluminium built, just 10kg heavier than its gasoline cousin...why can’t one of these engines be part of a hybrid...the main problem of Diesel is emissions while accelerating....why not let an electric engine share the burden during aceleration, keeping emissions low?  

RE: Why are most hybrids based on gasoline engines?

Indeed. Baffling isn't it?

Toyota say they are working on 10 hybrids. Maybe they are looking at a diesel electric.

Cheers

Greg Locock

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

RE: Why are most hybrids based on gasoline engines?

To TheBlacksmith...Gasoline is as smelly as Diesel, the difference is that gasoline “sweet” smell can cause you leukemia while refueling. When I’m driving my HDI engine at 150km/h I’m worried about that small aerodynamic noise, I almost can’t hear the engine...in fact Gasoline lovers now are saying the opposite, that they like hearing the noise when accelerating. Diesel smoke...only on hard acceleration and on Diesel engines without FAP... now there are a few special offers “buy a Diesel at the same price you would buy a gasoline”, as you can understand by this the price difference is not 5000€, mainly because of something Ford discovered a century ago(for some models you can only buy it Diesel, there isn’t enough demand to justify a gasoline engine)...Diesels are easier to start on cold due to heated high pressure(2000bar) common-rail....  

RE: Why are most hybrids based on gasoline engines?

(OP)
You know, 30-odd posts later and I'm still we engineers don't know the answer - I haven't heard a killer argument either way.

I used to travel from London to Plymouth almost every week on a massive diesel-electric hybrid.  Why would the rail operators use diesel as the power source if it wasn't optimal?

RE: Why are most hybrids based on gasoline engines?

You won't find an engineering explanation. The explanation is in marketing and costing

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Why are most hybrids based on gasoline engines?

Both gasoline and diesel engines have potential to be good hybrid engine. Even if diesel is generally good at lower rpm, it can also be tuned for good horsepower at high rpm. For example, the intake pipe length, port, valve lift and turbocharger can be tuned for high rpm rather than lower ones. next the vehicle can have relatively taller gear ratio if compared to gasoline engine in the hybrid vehicle.

Just like i mentioned before, the market perception toward diesel engine also carry weight when it comes to decision making on whether a diesel or gasoline for hybrid vehicle would be better.

RE: Why are most hybrids based on gasoline engines?

Someone hinted at it early on. Diesel engines are not made for start/stops as they require considerably more starting current. Therefore they would have to run longer to make up for that drain, defeating in part the reason to use them in the first place. Most farmers, truckers etc. start them once and run them many hours before shutting them down.

Gas and electric just seem to complement each other so very well. Sorry diesel lovers.

Life is what happens while we're making other plans.

Wally

RE: Why are most hybrids based on gasoline engines?

Oh, O.K. BigWallyB let me see...GM 1.248 ecotec cdti diesel engine -- about 10% more starting current than G.M. 1.364 twinport gasoline engine (same  power and 30% less torque)...now I'm pretty convinced (not to mention the generator could easily provide 10% more recharging current due to Diesel higher torque)...

RE: Why are most hybrids based on gasoline engines?

I really do think it comes down to diesels being noisy and smelly- which they undeniably are.  Much better than years ago, but still much louder than a comparable gas engine.

RE: Why are most hybrids based on gasoline engines?

Toyota Australia has offered every model here except corolla in diesel for at least fifteen years! I would expect only pugeot to have more passenger car diesels here than toyota.
Too much weight penalty having diesel hybrids, I'll bet hybrid car engineers would give their right arm for a spare 20kg for more battery

RE: Why are most hybrids based on gasoline engines?

Earlier this year EPA and Eaton announced a demonstration project where they would outfit a UPS delivery truck with a hybrid powertrain that includes a clean diesel engine and hydraulics. See http://www.epa.gov/otaq/technology/420f05006.htm

RE: Why are most hybrids based on gasoline engines?

Scootaroo claimed "Toyota Australia has offered every model here except corolla in diesel for at least fifteen years!"

Odd, Toyota Australia's site does not list any diesel options for Avalon or Camry (their medium/large cars). Autospeed doesn't list any secondhand ones.


Cheers

Greg Locock

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

RE: Why are most hybrids based on gasoline engines?

General Motors is currently selling busses in the U.S. that are diesel electric hybrids.

RE: Why are most hybrids based on gasoline engines?

I think Japanese OEMs are using gas hybrids not because they're more efficient than a diesel hybrid, but as has been said before they complement each other in terms of driving experience.

OTOH, 0-60 timies do not matter in a bus, where efficiency and longevity do.  Diesels can go 500K miles before a rebuild and are more efficient during cruising than a gas job.

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