My co-worker, a Geologist & Engineer with previous experience blending oils and small engine testing, said octane ratings are based on something called "Compression Ratios". He said the higher the compression the more octane would be beneficial. He also said you would only need a higher octane, like 91+, if the compression ratio was 10:1 or higher. He said that would be greater than 150psi. He said there's a lot of variables in determining compression ratios but that's a good rule of thumb. Not sure if this is correct with only chainsaws but this was his experience.
Short stroke high compression two strokes are a breed apart......they just don't detonate easily. Longer stroke two cycle engines are different though.....that's why what we learn on a motocross bike does not apply here. It about dwell time.......
We machine the squish band and cylinder base in a way that makes these engines even more resistant to detonation.
Even automotive performance engines have changed tremendously in these last few years. Now they have new engines from the factory making 10.5:1 compression ratios, and over 500hp that will run on ****** pump gas......even on ethanol based fuels.
How did they manage that? By running a tighter quench (squish) clearance, and smaller combustion chambers.
Proper squish clearances will increase squish velocity in a manner that resists detonation extremely well. Too wide and flat, or improperly tapered, and the crankshaft will die an early death though........
If you wanna go to school on this stuff........spend some time with your nose in the literature......it's everywhere these days.