-The proper ratio of spray to fuel:
Generally speaking, you want to be around 20 - 25% spray to fuel. any more and you could potentially (so I've heard) wash water down the cylinder walls and contaminate your oil sooner than you change it. Personally, I don't put too much faith in this since we squirt a lot more fuel in there, and the methanol burns too, so it should (in my head) just depend on how much water you're shoving down there. I have about a 25% spray to fuel ratio on average in my power band (less than 25 at 8500 rpm, more than 25 at 6k rpm.) You can determine the proper amount by calculating the fuel you use by multiplying your injector size * 4 then factoring in your duty cycle. Injectors are rated at 43psi from rc, and we run around 51 pounds of fuel pressure, so the injector flow is a little under what it's rated, but that changes with your boost curve, so close is good enough. For example, if you have a duty cycle of 60% on 650cc injectors in the middle of your powerband (say 7400 rpm), that's 650 * 4 * .60 = 1560 cc/min of fuel, so your methanol jet should be spraying at 1560 * .25 = 390 cc/min. If you are unsure about your jet, it's easy to flow test -- just take an empty oil bottle and point your jet there, trigger your pump, let it go for 30 seconds, let the foam settle, then multiply the ml by two for ml/min and there you have it (one ml is one cc, for those who didn't know).


-The proper air/fuel ratio to run:
First, understand that I'm about to use "air/fuel ratio" totally incorrectly here just because we're used to the gasoline air/fuel numbers. When you added the methanol, kmanager no longer reports the actual air/fuel ratio, but you can tune with the numbers just as if nothing has changed. You can run a much leaner air/fuel ratio now because the water removes 6 times as much heat as the fuel you were leaving behind, and the methanol will allow for a leaner mixture without detonation, and any remaining methanol will remove heat twice as well as the gasoline that remains as well. I generally tune for low to mid 12s on my car. I could go leaner. I don't. There's not much power leaner than low to mid 12s, so why risk it. Hell, just tuning n/a cars, 12.8 makes for practically peak power. Just to give you an idea how much cooling the water alone is providing, I'll calculate the air/fuel ratio you'd have to run with gasoline alone to compare to the heat removing properties of the water.

Latent heats in J/g
Water: 2257 J/g
Methanol: 1100 J/g
Gasoline: 350 J/g

Mass in Kg/m3
Water: 1000
Methanol: 737.22
Gasoline: 786.51

-If you are running 1560cc of fuel to 390cc of spray at 50/50 mass, that means about 44% of your volume of 390cc is water. That leaves 172cc of water to remove heat. If you were running
a 11.7 air/fuel ratio gasoline only combustion event, it has 80% fuel burned, and 20% remaining (.8 lamda.) This leaves .2 * 1560 = 312cc of gasoline with the 650cc @ 60% duty example. Using the above charts you can see that water weighs 1 gram per cc (you should know this from school), and gasoline weighs .737 grams per cc. 172cc of water weighs 172 grams. 312cc of gasoline weighs 230 grams. This means the water removes 172 * 2257 = 388,204 joules, where as the gasoline removes 230 * 80,500 joules. The water removes 4.82 times as much heat as the gasoline.

This means that if you wanted to remove as much heat as running just the water alone, you'd have to have 4.82 times as much fuel left over. With the 650cc @ 60% duty @ 11.7 a/f example from above, that means that 1560 * .8 = 1248cc of fuel is consumed and 4.82 * 312cc = 1498cc would need to be left over. That would put your air/fuel ratio at 1248 / 2746 = .45 lambda or an air/fuel ratio of 6.62:1. Not only would that not run well, if even run at all, you would need 820cc injectors, or larger!

Conclusion:
-Water cools best.
-Methanol increases octane.
-Extra octane from a higher methanol percentage comes at the expense of losing the heat removing properties of the water you replaced with methanol.
-Pick the mixture that works for your requirements.
-You can continue to tune with gasoline a/f as reported by kmanager.