Aero Nut,

The testing was on glow plug. I had intended to use one of these engines on a plane which would have a lot of electronics and I didn't want any potential interference from an ignition. Both the Shindawa and the Stihl produced great power on the gas/glow, but had extremely bad vibration in the 4000 to 5000 range. After a lot of reasearch and comments from others that have been posting on this thread, I came to the conclusion that the problem was ignition timing due to very high compression ratio. The mixes I used were intended to increase the octane rating of the fuel to offset the ignition problem. I finally setteled on a Homie 25cc on gas/glow and it works great.. The other engines did not have the mid range vibration when run on EI with syncrospark. I am using the Stihl on a H9 Ultra Stick and the performance is great on EI.