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Old 01-14-2013, 11:08 AM
steeny steeny is offline
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Originally Posted by prostcelica View Post
Hey guys

I think I know the answer but I thought id ask the guys that will know for sure. Say you had a 13:1 SBC but had a huge cam in it that made your dynamic compression ratio between 8-8.5:1 would it run on pump gas with out detonation. it is to much cylinder pressure that causes detonation right?

PS Im not planning on doing this. I just want to fully understand DCR

Built plenty of em this way> Not for the street!

The answer to your question no. Now to answer the question in the terms your thinking of yes and no. It has to do with the SCR and DCR, moreso the realtionship of the 2 terms. The bleed off of SCR by the cam will bring the cyl. pressure down till the design parameters of the overall build come together with the cam being the determining factor in this conversation. Once the cyl. pressuer starts to rise, the engine builds heat and compression, the filling and emptying cycle is reaching designed parameters with RPM rise...better have higher octane in the gas to promote adequate detonation suppression or it will eat itself to death! And if you think just limiting ign. timing will take care of the flame front and travel, it does not work that way!!
I could go on and on with theoretical entropy and enthalpy of a heat engine, gas laws, etc... but that is WAY to involved for here.

In is all about pressure, flow, engine speed minimums and a controlled burning for an intended application. Just scratching the surface on this subject! Its the meaning to the whole.