SOLOMIATA@aol.com wrote:
>1) Compression ratio (volumetric effeciency).
Uhh, no. That would be _thermal_ efficiency. You improve volumetric efficiency
with changes to ports, induction systems, larger valves, different cam
profiles, exhaust systems, etc.
I have to disagree with Mark re: P vs SP motors. Even though _some_ P cars have
limits on valve and venturi sizes/number of carbs, that is more than offset by
the allowance for any camshaft, any valve springs/valvetrain gear, any pistons,
any rods of ferrous material, and crankshaft, unlimited porting, lightening,
etc. Ask the NASCAR tuners if they can't find a way to get a restrictor-plate
motor to work at very high rpm. It's tricky, but it can be done. In P, you can
make all the changes necessary for an engine to live at very high rpm, and you
can reduce reciprocating and rotating mass much more than you can in SP. You
can also spend a _lot_ more money on motors if you push the P rules to their
limits.
Jay
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