Well I finally was able to test some of the higher-octane fuel mixes. Still do not have the Shindawa ready to go, so I mounted the 35cc Stihl on the test stand. I made several runs on the following mixes:
1/3 ST glow, 2/3 93-octane w/10% ethanol.
1/3 ST glow, 2/3 93 octane w/ 10%ethanol and 10%toluene.
1/3 methanol, 2/3 93 octane w/ 10% ethanol, no nitro.
1/3 ST glow, 2/3 93-octane w/10% ethanol added 3 ml Permatex octane booster.

All of these mixes improved the overall vibration level to an acceptable level at 1500 to 2500rpm and 5000 rpm plus. Vibration in the 3000 to 4000 rpm range was higher than I would like it to be. The only run which significantly reduced the vibration in the 3000 to 4000 rpm range was the run with the Permatex octane booster added. However, as I suspected the MMT, which is an organo metallic (manganese) compound, fouled the glow plug after about 5 minutes run time.

I tried one other mix just to get the maximum octane level which was 1/3 methanol, 1/3 ethanol and 1/3 toluene. If my calculations are correct, this would give an octane number of 113. The engine would only run with the glow plug on. There was virtually no vibration in the 3000 to 4000 rpm range, but WOT rpm dropped from an average of 8200 on a 18 X 8 to about 5200 rpm.

I guess it is back to the drawing board since fuel mixes didn’t get me where I wanted to be.

Merry Christmas and Happy Holidays to all and may you have a great New Year.

Will