Invisible wrote:
> Actually, you laugh, but I did see a report about a car that has a giant 
> motor inside it that drives the wheels at low speeds, acts as a starter 
> motor to start the petrol engine when the car is moving fast enough, and 
> acts as an alternator to charge the batteries thereafter. Basically the 
> petrol engine only runs while the car is doing more than 20 MPH. The big 
> advantage being that waiting at traffic lights uses no fuel.
> 
> [Actually, having computed that my car uses 10^(-6) L of fuel per minute 
> even when it's flying down the road at 75 MPH, I wonder just how much 
> fuel it can possibly be wasting on tickover? And also, doesn't 
> repeatedly starting up a petrol engine waste fuel anyway?]
> 

I'm having trouble with that math, but it could be that I haven't looked 
at a diesel car in a while. My sisters car got, lets say 35 miles per 
gallon when running at mostly highway speeds. I'm probably 
underestimating it a bit, it was a small car. At 70 mph, that's 2 
gallons of fuel an hour. 3.78 liters in 30 minutes, gets .12ish liters 
per minute.

Unless you are coasting all the way downhill in both directions.

> Last I heard the car never came to market. They were still playing with 
> the control software to try to figure out the most optimal algorithms...
> 

They have gotten it working, the Toyota Prius does just that. It can run 
on the electric motors up to around 35 MPH, and cuts the petrol engine 
off when ever it doesn't need it. The batteries for the electric system 
charges off of both the petrol system and a regenerative braking system.

What's really odd is riding in one of these cars when the petrol engine 
cuts off at highway speeds. The car just decides that going down hill is 
easy, and the driver is braking anyways, so who needs the engine?

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