Russell McMahon wrote:

> Now start expansion.
> At zero stroke you have 300 bar. At 1/300th of the stroke you are down to
> 150 bar (already) as volume has doubled. At 2/300 of stroke it's 100 bar. At
> 3/300 or 1% of stroke its 75 bar. And so it goes on. At 50% of stroke
> pressure is about 2 bar ! You need a very special expansion engine to handle
> such wide expansion ratios efficiently.


Which is why turbines etc have rotors of differing
sizes as the gas reaches lower pressures and higher
velocities. Did they specifically say that the car
was piston powered?

A properly designed turbine may have other advantages,
ie; flywheel effect, which has already been considered
for electric vehicle use as it can give a bit of
"oomph" to a paltry 6kW average vehicle.

Slightly OT, but I once saw an "economy marathon" type
vehicle with variable-diameter flywheel, so energy could
be fed into it (or drawn out like a spinning ballerina)
-Roman

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