It doesn't cool the b|00dy engine, nitrous oxide injection is
very much like a supercharger or a compression ratio increase in
that, during combustion, it can dramatically increase the dynamic
cylinder pressure in the engine, due to its higher percentage of
oxygen content than does the air in the atmosphere.
If you feed nitrous to the engine without enough extra fuel, the
lean air/nitrous to fuel mixture will make the detonation problem
even worse. Combustion temperatures will skyrocket and catastrophic
failure is certain to occur. If the proportion is such that too
much fuel is delivered, the power advantage degrades rapidly.
