QUOTE(TimT @ Mar 17 2007, 07:22 PM)
QUOTE
The relationship of compression pressure to compression ratio is a complex one, and rather non-linear
Now thats not really scary at all..Im a math geek.. MS in engineering etc..
OK, then start doing some modelling... Figure out all of the factors that go into piston speed (battery, electrical path to and from the starter, etc.), figure all of the places you're going to lose pressure (cam overlap, valve-to-seat interface, rings, etc.). Then dig out the chem textbooks to look up adiabatic reactions, and grind through what sort of pressure increase you can expect with the volume reduction at a given rate minus the escaping gas at a given rate. Then remember that the air will heat up as you compress it, which changes the pressure... (Oh, and don't forget to take water vapor into account!)
That's about ten steps past where I get a four-alarm headache and say, "f--k this!"
If you have friends who design auto engines for a living, you may be able to get a decent model out of them. Otherwise, it's probably best to just say "high numbers good, even numbers better, low numbers bad". Which even a programmer like me can remember!!
--DD