Re: Water Injection
Atmospheric humidity has a net decrease effect on engine power output. But fluid injection has a net positive effect. Here's the difference:
Atmospheric humidity results in less mass flow of the working fluid through the engine heat cycle. Also, fraction of combustible oxygen is reduced in the working fluid.
On the other hand, water/alcohol injection significantly increases mass flow of the working fluid, AND heat is required to vaporize the injected fluid (while atmospheric humidity is already vaporized), thus reducing engine temperature significantly and thus allowing more fuel input, thus more power.