ORIGINAL: Konrad
So are you saying that the European engines that use low or no nitro are not in danger of over heating from the alcohol flame? That the danger is from friction. Over heating in my definition is where the high temperature allows systems to fail. In the case of our engine the seal between the piston, cylinder, ring or the film strength on the rod journals. Over temp is not limited to changing of the material characteristics (size, grain structure or oil film strength).
Correct, the lean condition does not cause the flame temp to rise to cause the overheating, but the lack of oil increases friction causing overheating. But as I said there are exceptions. High nitro is one because it makes its best power the richer it is, but will burn an engine up at its ideal mixture. I will add that I was refering to overheating in the context of permanant damage to parts. Of course it would be reasonable for you to consider getting hot enough to burn out plugs, or to run rough, as overheating, even if the mixture is not lean and no parts are damaged. Then in that contextthen your original thought is probably correct.