Originally posted by tcodi
Why is a lean mixture more prone to detonation?
Why does a lean mixture burn hotter?
Combustion needs 2 ingredients to occur. 1 Is a hydrocarbon like gas, the other is oxygen. Oxygen is found in the air around us, but only in a small percentage. (about 15-20 % oxygen). the rest of the "air" is made up of nitrogen which doesn't burn. the optimum ratio for the best combustion is about 14.5 to 1 or so. ( That's 14.5 parts air to 1 part fuel). more like 12.5 to 1 if your building a race engine. I could be off a little on those numbers but that's fairly close I believe.

So, to answer your question. Oxygen burns really hot. Maybe a chemist can stop by here and tell you why that is, cuz' I'm not 1. But, if you run your engine below the 14.7:1 meaning too much (Hot) oxygen it will run (Hot) just like an acetylene torch does when you hit the oxygen lever. More oxygen = more complete burn of the fuel = more heat. If you run a richer mixture you in turn have a lower oxygen % in the mix and more fuel so a less complete burn = lower combustion temp. Don't know if that answered your question, but it sure got me confused.