I was thinking about performance mods for a 997.1S 3.8L M97 engine, and wondered how difficult it is to take advantage of a higher octane fuel.
Here in California, we only have 91 octane at most stations, even though the engine is designed for 93. Fortunately, 100 octane is readily available for a reasonable price (I don't commute with the car, so $9/gallon is fine).
To some extent, the ECU can increase the compression and produce more power with higher octane fuel by advancing the timing. However, there is a limit to this. With a custom dyno tune, how much could the timing be advanced to take advantage of a given octane? In other words, could you program an ECU map to extract power from 95 octane?
Secondly, let's assume you wanted to go all of the way and build an engine for 98 octane. To do this, I assume you need some way to mechanically increase the peak engine compression ratio. What is the lowest cost and/or least destructive way to do this? Can you just insert a thinner head gasket, or do you need to actually mill down the head? Or what?