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.

 

[j2bprometheus]

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.

 

[j2bprometheus]

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

 

[Sorex]

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

 

[dgallup]

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.

 

[SomptingGuy]

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.

 

[drwebb]

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.

 

[kenre]

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

 

[mloew]

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.

 

[tbuelna]

"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.......

 

[tireland]

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.

http://www.L3Research.com

 

[Northboundtrain]

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.

 

[rdd48856]

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?

 

[GregLocock]

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.

 

[rdd48856]

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....

 

[SomptingGuy]

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?

 

[patprimmer]

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

Regards

eng-tips, by professional engineers for professional engineers
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[Azmio]

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.

 

[BigWallyB]

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

 

[rdd48856]

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)...

 

[bobqzzi04]

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.