On Wed, 21 Dec 2005 23:00:38 +0000, Chris Bacon
wrote:

Ian Stirling wrote:
Current car engines are about 25% at best efficient, so 75% of power goes
out the exhaust pipe wasted.

I thought most was lost through the radiator.

Cars are about 30% efficient at peak, usual operation is about 25%.
Cooling power = engine power is reasonable rule of thumb and assume
the remainder (33% up to 50%) goes down the exhaust pipe. Some of the
cooling is direct to air from hot under bonnet surfaces. Not enough
heat goes down exhaust pipe to run ancillaries at town road speeds and
idle. 70mph only needs about 35bhp, so maybe as little as 35bhp or up
to 50bhp goes to exhaust. They claim to extract 15% extra giving
about 5bhp at 70mph which would just about do for the ancillaries but
not with air-con.