Well my memory didn't serve me farther then remembering the book to look the facts up in.
From:
Motorcycle Tuning for Performance, by Carl Shipman Copyright 1973
"The reason power is reduced" (my note: And therefore temperature) "is a complexity. The chemical reaction between gasoline and air requires some elevated temperature to start it, after which it should generate enough heat to maintain the burning process.
Combustion moves outward from the point of origin (the spark plug) just like a grass fire spreads from the burning match that started it. Each part of the periphery of the flame front raises the temperature of the adjacent fuel to the combustion temperature. If the grass is green, wet or not present, it won't burn.
Similarly, if there are an overabundance of fuel (gasoline) molecules in the combustion space, they tend to insulate one set of burning fuel-air molecules from the next set and prevent the transfer of heat outwards to unburned mixture. This leads to unburned" (My note: un-used) "pockets of the air and possibly pockets of mixture that never burn at all.
There are other factors. The vaporization of excess droplets of fuel tends to cool down the entire combustion volume, reducing the effective pressure. The fuel vapor exerts part of the total pressure in the cylinder, during induction, reducing the pressure which the air can attain, and thus the weight of air in the cylinder." (My note: reduces the overall amount of fuel air charge, read heat potential)
"The net effect is that power" (My note: and therefore heat potential) "is reduced when the mixture is made rich..."
"Major internal cooling results from evaporation of the fuel droplets..."
Just remember _YOU_ asked. <VBG>
HTH!
