#33858, "RE: lets answer this once and for all" In response to In response to 4
okay, i think the answer that is being looked for has not been addressed. compression is the ratio that the piston can compress the air fuel mixture in the cylinder during its stroke from bottom to top. On say a 10.5:1 compression you would be able to compress tha AF mixture to 10.5 times its original volume. So you would have say a compression pressure of say 210 psi during a compression test. On an 8.8:1 compression you are only compressing the AF mixture 8.8 times its original volume therefore only creating a compression pressure of say 160 psi. so taking these numbers into account with regards to power delivery. the 10.5 pistons will make more power while not in boost and require less boost to make a certain amount of power say 200HP. the higher compression ratio can compress more AF into one stroke than a LC can, but you can compensate for this by increasing boost. Say a HC cylinder can compress 10 parts of AF mixture at 0 psi boost. and the LC piston can only compress 8 parts of AF mixture at 0 psi boost. you can see how the LC will make less power because it is actually compressing less AF. now if you put some boost in say like 3 psi or something, it will raise the 8 parts AF to like 10 parts. then the 8.8 will be making the same power as the HC pistons at 0 psi boost. so you could ultimately make the same power on LC pistons as you do with HC pistons, but you would have to use more boost. that is why HC piston cars seem much faster, they have more low end torque due to the fact that they don't need as much boost to create a given amount of power, while a LC car would have to wait for the turbo to spool and build boost before it can reach the same given amount of power. now the reason it is much easier and safer to tune a LC car is because of the boyle's ideal gas law the more you compress the mixture the hotter you heat the air. so on a HC car you are producing intense cylinder temperatures just from compressing the air, while on a LC car you aren't quite heating the air as much from the compression. that's basically all my ramblings for now. it may or may not make sense. lates James
