I did some reading on Gami G100UL fuel that is working its way as a replacement for the 100 LL. This company has spent years developing a potential direct replacement for 100LL fuel. Reading their testing, they utilized a number of engines including a Turbo Continental TIO 550 with 8.7 to 1 compression ratio. This got me thinking about our experimental engines. I run 9:1 and I know there are engine that run up to 10:1, so I sent a question to Gami regarding how their fuel would work in higher compression engines. I received a response the same day, which I did not expect. Here is the answer received from Gami…….
The "lean rating" octane performance of the G100UL exceeds that of 100LL, so any engines that can run on 100LL will run well on G100UL.
That being said, the "rich rating" octane performance is WELL above that of 100LL (160+ octane equivalent). I don’t know what the limit of detonation-free compression ratio would be when full rich. That limit might be hard to find using currently available engine parts.