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Originally Posted by getstroked
i might be confused here but how does piston speed affect compression? With the online calculators the motor should be running about 10.5:1. If so how come it runs fine on 87octane here is SD? I have always been told with the 76 cc heads that the ratio is about 9.2:1. Are the calculaors and what i am told be the difference between static and dynamic compression ratio?
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You can run a high compression engine on lower octane fuel with a large over lap cam as the dynamic compression ratio is much lower at low rpms, as the cam over lap reduces the the running compression, at higher rpms this effect diminishes and less timing and lower compression is required to reduce detonation.
04-29-2006, 02:42 AM
