"Jon Elson" wrote in message
...
Ignoramus6950 wrote:
...
An internal combustion car, burns fuel inside cylinders and
produces
energy according to Carnot cycle. Say, it makes 28% of energy from
the
total BTU of fuel that it burns.

Not even close. A good Otto-cycle engine gets maybe 13% efficiency
at near wide-open throttle. At typical mid-throttle operation, it
is
much worse, maybe 5-8%. A semi-Atkinson cycle engine like in my
Honda Civic Hybrid does better at mid-throttle, as does a Diesel by
eliminating pumping losses.
Jon

My 1949 Aircraft Powerplant Handbook puts the typical engine output
power at 29.5% of the energy in the fuel at cruise, 60% of rated
power.
http://en.wikipedia.org/wiki/Brake_s...el_consumption
The R-3350 (B-29, DC-7) was better at 33.7%, close to the top of the
range for the most efficient gasoline car engines. It used an exhaust
power recovery turbine system that's much too complex and expensive
for an economy car.
http://en.wikipedia.org/wiki/Turbo-compound_engine

jsw