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Dynamic compression doesn't mean anything on a race engine. Once the engine is up on the cam you'll have 100% compression if not more due to the ram tuning.


This also means that the crutch of using a "big" cam to bleed off cranking pressure to run lower octane w/ a higher CR only works up through a certain RPM range before the engine's static CR is driving the WOT octane requirement.

That's not my opinion, that's info that came from both a successful cam grinder and an engineer for a race fuel company.



If you run the numbers you'll see that most race engines have dynamic compression ratios down around 9:1 or so. Even Pro Stock engines. They certainly don't run those on pump gas.

The dynamic compression ratio doesn't mean anything when picking a fuel for racing. Once the engine speed gets into a range where the cylinder is getting a full charge of air then you need good gas.

Call any race fuel engineer and ask them or look on their websites. Nobody picks fuel by dynamic compression ratio when racing, all of the charts are static compression ratio.