OK, I appreciate that there is a lot of history behind water injection making power and keeping motors from blowing up at high power densities.
That said, what the water really does is cool the incoming charge, retard the burn rate in the combustion chamber to reduce pre-ignition, and provide an additional quantity of working gas for the engine to expand and produce pressure. In any installation and technique listed here, we need to separate these three effects.
I could go into a long explanation of the physics and my own experience with large bore engines, but it would be better to have you guys talk about your own experience within these three categories.
Specifically, cooling the intake charge without affecting anything else has advantages and effects equivalent to running on a cooler day. Retarding burn rate to reduce pre-ignition (as opposed to detonation) is a separate effect that requires a higher amount of water. Reducing pre-ignition through TBC's, smoothing sharp edges, or other chamber effects has to be compared to water injection without the penalties of injection. Last, the best use of water is to absorb excess heat where we know we simply have too much heat in the combustion chamber and need to stuff some more inert mass in there (beyond the nitrogen in the atmosphere) to absorb it and push the piston down instead of melting it.
All of this has to be understood independent of the addition of methanol (a fuel) and all of its issues.
LSR has lots of good information, and lots of mythology on water injection. To understand when and how much water to inject, we have to separate all these effects and turn the mythology into fact.