MW50 -Secondary effects were cooling of the engine .

[Letum]

Due to the cooling effect of the water, aircraft engines can run at much higher manifold pressures without detonating, creating more power.

I think this is wrong.
My understanding is that it's the methanol that causes the engine to run cooler, not the water. The water is just there to prevent the methanol from causing premature detonation.

edit: Looks like I'm wrong.