# Diesel Electric Cars



## WhoozOn1st (Sep 18, 2009)

L.A. Times Pulitzer Prize-winning (for auto reviews!) columnist Dan Neil is at the Frankfurt Motor Show.

European carmakers rev up the electro-diesel concept

"The [Volkswagen] L1's marquee number: 170 mpg, or about four times that of a Honda Insight hybrid. If it comes to market as planned in 2013, the VW L1 could claim the title of most fuel efficient passenger car on the road.

"It would also be one of the cleanest. On a carbon-gram-per-mile basis -- that's the emissions metric that Europeans are most concerned with -- electro-diesels can outperform the thriftiest gas hybrids on the planet."

Volkswagen L1


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## Rumpled (Sep 18, 2009)

I saw the article this morning, but haven't read it yet. I'll get to it.

I've long thought that a VW TDi type engine with a hybrid would be very good. Since VW TDi's already get nearly 50 mpg before going hybrid.

You could probably make the engine as small as 1 liter to run a small car.

Comparing these concept cars to current production models may not be very like for like; it's more apples and oranges.

On "normal" cars; if they just had enough battery to power accessories (AC!) at idle and turned the engine off, we'd probably get about 30% better mielage in the city w/o paying $4K+- to go full hybrid.


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## WhoozOn1st (Sep 19, 2009)

Rumpled said:


> Comparing these concept cars to current production models may not be very like for like; it's more apples and oranges.


Often the case.

A major reason for posting the article is that I'm so often astonished that folks - even readers of these forums - are unaware that many Amtrak locomotives are diesel electric; laboring under the misapprehension that some sort of carlike mechanical/hydraulic transmission applies the diesel power to turn the wheels.

Here we have tried and true rail power principles being applied to automobiles: Diesel engines driving generators, alternators, what have you (very complex these days), which convert the internal combustion motion into electricity for further conversion to the tractive effort (motion) that pulls (or pushes) the train.


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## railiner (Sep 19, 2009)

WhoozOn1st said:


> Rumpled said:
> 
> 
> > Comparing these concept cars to current production models may not be very like for like; it's more apples and oranges.
> ...


The soon to be in production Chevrolet Volt is just that, except it's a gas-electric. Unlike the hybrids, the gas engine never is directly connected to the cars transmission. If fact there is no transmission. Rather, it is an electric car, that has a small gas engine on board to charge the traction battery, when its plug-in charge runs down, or its regenerative braking charge is insufficient to alone extend the charge. The engine does not provide additional boost to the cars performance like a hybrid engine does.

As for diesel powered rail equipment... years ago the Budd RDC was diesel engines driving a hydraulic transmission. There were no electric traction motors. This make these cars uniquely able to move thru flood waters in an emergency.

The UPRR for a brief period tested some German made diesel hydraulic freight locomotives. They were not successful.


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## Green Maned Lion (Sep 25, 2009)

While they happen to operate using the same equipment, they operate with different principles and for different reasons. The reason a diesel locomotive uses electric traction motors is: transmissions that can transmit 1500+ horsepower (like, say, 6000 horse power, for instance) while under a load of thousands of tons simply don't exist. Especially not reliably.

As for why that car is so fuel efficient, it is mostly the shape. Volkswagen's 1 Litre concept car from years back ran on diesel without the hybrid stuff and it got better economy than this. Actually, it exceeded its design concept, which was 1 litre of fuel per 100 kilometers. Tandem 2 seater. Made its debut at Ferdinand Piech's retirement party, if I recall correctly.

Still, the best economy this thing can get is 340 passenger miles per gallon. Still way under what a train can do. Or even what a 15-seat Sprinter can do- 375.


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## jis (Sep 25, 2009)

Green Maned Lion said:


> Still, the best economy this thing can get is 340 passenger miles per gallon. Still way under what a train can do. Or even what a 15-seat Sprinter can do- 375.


Assuming that the 15 seat Sprinter gets that pmpg with all 15 seats occupied, just as a comparison point my - now legacy hybrid technology Prius can and does get 250mpg regularly assuming all 5 seats are occupied.

A diesel-hybrid designed right would be very considerably better performer energy consumption wise in terms of yield per gallon. Afterall diesel *is* a richer source of energy since the enrgy density of diesel is significantly more that gasoline.

Every stage in the transmission costs some energy loss and hence the designers try to minimize the stages required. Also nothing comes close to the almost 100% efficiency of a mechanical link between the motor and the wheels. Hence designers of hybrids try to make the high speed run primarily on a mechanical connection. A car that has a drive train which goes motor -> electric -> wheel for all situations is unlikely to be as efficient as a system that is capable of doing motor -> mechanical + electric boost from battery -> wheel at low speeds, motor -> mechanical -> wheels at cruise (perhaps with some bleed charging of battery to emulate pumping loss), and regenerative braking charging battery during deceleration. Today's most efficient hybrids use the last combo.


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## DET63 (Sep 25, 2009)

railiner said:


> WhoozOn1st said:
> 
> 
> > Rumpled said:
> ...


Weren't some of the early TEE passenger trains in Europe diesel-hydraulic? At the time, there was no standardization of European power supplies (some countries used AC, either at 50 Hz or 162/3 Hz; others used DC, and voltages varied from 1.5 kV to 25 kV), so diesel was used instead. Once power supplies were standardized, or electric trains were developed that were compatible with multiple systems, the diesel TEEs were retired (or relegated to other services).


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