VERY cool new cars

[Wombat]

Hmm, I wonder why there are no hybrids available that are diesels?

Diesel's high operating temperature? I'm just guessing. You've got to keep diesel under heat/pressure, and that doesn't seem like it would work well with the instant on/off requirements of effecient hybrid vehicles.

[az]

Would the frequent restarts actually be necessary with a large battery and big caps? I thought what made hybrids superior was that their gas engine could always run at its favourite speed, not that it only runs part of the time.

[az]

But why are there no gas (and I mean gas, not gasoline) turbine hybrid concepts? There are even gas turbine production cars. Or biodiesel hybrids? Or Ethanol hybrids?

[Kooldino]

I was wondering that myself. And mazda should make a Wankel Hybrid

Haha, wankels are not known for their fuel economy. But I guess it couldn't hurt to play around with it.

[Kooldino]

Diesel's high operating temperature? I'm just guessing. You've got to keep diesel under heat/pressure, and that doesn't seem like it would work well with the instant on/off requirements of effecient hybrid vehicles.

Hmm, but they do seem to fire up as quickly as a gas engine does.

Perhaps if your guess is correct, they could make the engine run 100% of the time, but when on electronic assistance only inject enough fuel to keep the engine from stalling.

[Kooldino]

Would the frequent restarts actually be necessary with a large battery and big caps? I thought what made hybrids superior was that their gas engine could always run at its favourite speed, not that it only runs part of the time.

Not that I know of. Besides, an engine's favorite speed is only good for producing max torque. You don't always need that. It would be wasteful.

[Kooldino]

But why are there no gas (and I mean gas, not gasoline) turbine hybrid concepts? There are even gas turbine production cars. Or biodiesel hybrids? Or Ethanol hybrids?

Convenience.

Where are you going to fill a bio or ethanol car in the US? Diesel would be a more logical step to take.

[MultimediaMan]

Gas Turbines can be very efficient, but they do not scale down well. Also maintenance on them is a nightmare....there are very good reasons why a "little" (100-600 SHP) one costs $50,000+ USD.

The most efficient Gas Turbines in the world are stationary and used mostly to produce electricity from Natural Gas - I think they are almost 35% efficient for the biggest GE models.

The most attractive thing about them is that their duty cycles are extremely good...on the order of a year or so before they need to be taken out of service for an overhaul. Nothing else comes close to that long of a duty cycle in power generation other than Hydroelectric power.

[Edit] Gas turbines can theoretically burn nearly anything, so running ethanol, biodiesel, diesel or JP-A is not really much of an issue. Thermal efficiency of small gas turbines is horrendous, however. [/EDIT]

[Wombat]

Perhaps if your guess is correct, they could make the engine run 100% of the time, but when on electronic assistance only inject enough fuel to keep the engine from stalling.

You mean idling? That's what burns up your gas as it is. Even without electronic assistance, if your current engine could instantly, efficiently turn off at stoplights, and when coasting, you'd see a significant increase in fuel efficiency.

[Kooldino]

Sure, but idling the engine vs running it under load is night and day when it comes to fuel consumption.

[Wombat]

You missed my point. Your engine is ALREADY idling when not needed. But that's still a significant/majority of the time you're in the car. A hybrid with an idling engine would be just like a conventional car, and have the same lousy efficiency.

[Kooldino]

You missed my point. Your engine is ALREADY idling when not needed.

You missed my point - My engine is doing work and burning a lot of fuel when I'm cruising. If it was run off of electricity during certain situations such as that, it could be better off.

But that's still a significant/majority of the time you're in the car. A hybrid with an idling engine would be just like a conventional car, and have the same lousy efficiency.

I highly doubt that. On my average 20 minute commute to work, I probably sit at idle for about a minute. I probably spend another minute or so accelerating. That leaves 18 minutes of cruising that I could have improved economy with an electronic assistance, for instance.

[JTD]

Hmm, I wonder why there are no hybrids available that are diesels?

They are coming.

PSA Peugeot Citroen has prodcued a protype diesel/hybrid: http://www.greencarcongress.com/2006...ugeot_cit.html

[Brian Ellis]

Hmm, I wonder why there are no hybrids available that are diesels?

This is discussed at http://www.cypenv.org/smf/index.php?topic=71.0

I believe the French prototype is problematic because of pollution issues. I've heard that production is unlikely to start before 2008-2010 and this is probably an indication that there are still many bugs to fix, otherwise they would be starting on a winner by next year. I know Toyota has had what they consider insurmountable (for the moment) problems with diesel hybrids, but I think their difficulty was to find the compromise between engine weight and longevity on a start/stop regime.