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I completely disagree with the statement about 11.5:1 compression ratios. Nothing above 10:1 is compatible with pump fuel for many engines of the last 20 years, eg my BMW M635 with a Motronic 2 ignition and fuel system. Some exceptions for the very latest engines newer than 2003 or so and even then they still do not run at optimum perf with fuel less than 94 octane. Air cooled Porsches are even worse. Add almost one full point of compression for fuel requirements, eg 10:1 Porsche is effectively 11:1 water cooled for octane requirements.
As for real engines that run 12:1 and higher compression ratios, tetra ethyl lead added to make 110 octane or higher is what really cooks. Nothing smells better than racing gas, and nothing sounds better than REAL high compression engines, eg 16:1. And nothing RUNS better either.
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