Justin,
The static compression ratio of an engine is worked out by using the total
volume of the cylinder at bottom dead centre / by the total volume at top
dead centre. It doesn't take into account the camshaft or valves. The
dynamic compression ratio is affected by the amount of overlap the camshaft
has since if both valves are open for a long period you'll get charge air
going straight out the exhaust (which is also a reason why you get poor fuel
consumption with a meaty cam) so the meatier the cam the less the dynamic
compression ratio is. Handy thing is a 74 degree cam when your compression
rings are on their last legs :)
- Tom
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Justin
Friedrichs
Sent: Friday, 16 March 2001 1:19 PM
To: '[EMAIL PROTECTED]'
Subject: COMPRESSION RATIO
HI LIST
Why would the compression ratio change with a different cam?
Isn't the CR measured when the valves are closed, so the cam shouldn't make
any difference. The only way I could see a different pressure reading would
be if the cam was opening one of the valves. But I spose the pressure would
be zero.
Justin
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