Just so you don't think Ed is picking on you, I'll chime in that I agree with him. 18:1 on any pump gas just ain't happening. 11:1 maybe...10:1 to be safe. Even if you did go to alcohol, 16:1 is about the max there. If any engine builder told me I could go to 18:1 on pump gas, I would be running away as fast as I could...if I could stop laughing long enough to run that is.
George