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Something similar is gunpowder. I think alcohol works better with high compression. I believe alcohol burns slowly which would be why it can handle much higher compression ratios than pump gas.
Fast burning gunpowder versus slow burning gunpowder. If you use two powders of greatly different burn rates you can actually feel the hottest portion of the gun barrel move out towards the muzzle, versus the slower powder burning quicker and the hottest portion of the barrel would be nearer the breech of the gun.
I remember my brother loaded some 7.62 X 54 R ammo with 20 MM cannon powder that he got for $4 a pound surplus. The powder burned so slowly it would not completely burn in a 30 inch barrel. The chamber end was fairly cool while the muzzle was much warmer than a few rounds of normal burn rate powder.
That was what I thought about when he described the temp difference between the cylinder head and the exhaust. I would imagine it also had something to do with the actual amount of fuel that you have to deliver to the combustion chamber with alcohol, with that volume of fuel actually contributing to the cooling of the combustion chamber.
Christ, I think it is actually the alcohol burns slower, and the much larger volume of fuel keeps the combustion chamber cooler by absorption, but it is really only a guess on my part.
regards
Mech
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