ORIGINAL: pe reivers
the only gas engine that comes very close to 1.60 FX powerwise is the MVVS 1.60 (about 90% power). The modern ICU ignition uses LiPo ignition batteries, so the weight disadvantage becomes real small.
For flight, a 10 oz fuel tank will do. This cancels out the extra weight of the ignition. Add to that the lesser vibration of the gasser, so you need less vibration isolation, and the difference gets even smaller.
Is your 90% power reduction with both motors on pitts mufflers? You are saying that if my OS16FX pulls 18 pounds of thrust the MVVS 1.60gas will pull 16.2 pounds of thrust?
That is about the differnce between my OS160 and my OS108, both on pitts.