Without going too deeply into this, I have always understood the main reason water injection worked is the heat required to turn water into super heated steam during combustion did 2 things:
1. It lowered the temperature of combustion thus lowering the flame front speed and therefore detonation, and for the same reason it reduced NOX emissions.
2. Superheated steam, takes up more room than the water that was used to create it, and therefore actually raised the compression ratio during combustion, allowing the engine to make more power, even though it has slightly less oxygen to burn.
It is because of these two effects engines run smoother and make more power when supplied with cool moist air.
Regards,
W.B.
