Have had this thought rolling around in my mind for a bit. I think we touched on the subject years ago. Can't find the thread though.
an AFR is stoichiometric, then presumably all the oxygen in the air is reacted with all the fuel in the air and there's none of either left over.
Any AFR richer OR leaner than stoich is actually cooler in the cylinder than it would be at stoich...
Why is max power achieved at AFR's slightly richer than stoich? In thermodynamics, for a given mass of gasses in a given volume, more heat is more pressure.
I'm curious what your thoughts are.