High MPG

Gary Derian gderian at cyberdrive.net
Mon May 4 17:44:07 GMT 1998


The efficiency, in terms of fuel used for power generated, of an internal
combustion engine has to do with expansion ratio, combustion temperature and
pumping loss.  2 valve, 4 valve, pushrod, OHC, etc have little or no effect
on efficiency.  High winding multi valve engines get more power per
displacement but not necessarily more power per weight or cost.  Maybe you
con't like pushrods, or they are aesthetically displeasing to you but they
are certainly not less efficient.

A gasoline engine wastes only 60% of the energy in gasoline when operated at
full throttle.  It wastes 80% at part throttle where it operates like a big
vacuum pump with a leak and it wastes 100% at idle.  Multi-valve and
overhead cams don't change these numbers.

Gas turbines, steam, rotary, etc generally do worse.  The road to
improvement is paved with reduced heat loss from exhaust and cooling.
Ceramic parts which operate without cooling and greater expansion ratios can
reduce this energy wastage.  None of which has anything to do with pushrods.

Gary Derian <gderian at cybergate.net>

<snip>

>I think pushrod engines waste something in the neighborhood of 80% of the
>available power in the gasoline.
>
>Frederic Breitwieser





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