Mike there is a way around the petrol thing, this is the bit the model RC guys are convinced is over unity, i have just tried again and it isnt, True a glow uses more methanol fuel that a petrol engine, but a petrol engine is much heavier, also note a small diesel out does both by a long long way.
Now the over unity bit your just going to have to try yourself. You can run a 2 stroke GLOW engine with a GLOW plug and not a spark plug on petrol, seriously this is true because i have done it and done it again tonight, NO timing used no modifications to the engine except when power is applied to the glow plug at low rpm. If you know that Methanol burns on its own with platinum as a catalyst, then the reasons seem fairly clear, to lower fuel consumption i mix ethanol in. Its got more punch but dosnt burn as well on its own, also you need it bone dry, so 3A molecular sieves in the tank and fresh dried ETOH only.
Now add 3-5ml per 150ml of fuel of petrol, that 3-5ml of petrol adds some serious punch but the down side in a RC plane is speed, the engine cant run slow, in a quad it dosnt matter as your not landing with the prop. Heat is the big issue with this mix, I way trying all kinds of tings to try and negate the heat problem. Also the glow plug matters, i dont know the number of the one i used, i know its made by OS and i think its a number 3...... I need to buy a couple and try them again.
Engine size, i dont know much about RC engines, most the ones i tried (i got roughly 40 odd beat up ebay ones) range from .25 on the body to 10cc. The ones that work best are the medium ones, they have 65 on the engine body, no idea what that is in CC. I know its under 10cc because they are smaller. I will video my bench runs, GLOW plug and petrol and Glow plug and my fuel. Decent caps would help because my motor i use as the generator knocks out 75V, I dont remember the electric drive motors now, but they were from sil labs dev kits, i still have them. I do remember that full chat they pulled 14A and were nasty to get near. This is why i had to sequence them because the power consumption was high.
Let me get some work out the way, i will then do some videos. But i would honestly put my engine up against a petrol any day, I am positive fuel wise I would come out on top. Dosnt work with castor oil, not sure why but carbon is one issue and the burn isnt right, but normal mower synthetic oil works fine if mixed with a tiny drop IPA or Trichlor if i run out of IPA

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