The following charts are calculated based on:
10Kg of air, Gasoline's latent heat capacity of
350KJ/Kg
Water's latent heat capacity of
2256KJ/Kg
Methanol's latent heat capacity of
1109KJ/Kg
Injection water at different ratio to fuel at 100% water and 75% Water/25% Methanol. You can see the at 100% water injection, only 3% of w/f fuel ratio is enough to replace 2.5 point of a/f ratio (dotted line). As soon as 25% of Methanol is added, the a/f ratio is dropprd to 12.0 - loosing some cooling capacity
Each of the following chart show a 25% percent increase in Methanol concentration of the mix.
lastly, just methanol is added and no water. The chart on the right is 100% water
The two charts show (first and last) that you will require to inject twice the amount of methanol to equal the latent heat of water alone. Methanol is relatively low cost and very effective as a coolant so what is the problem?
When higher concentration of methanol is injected, you need to lean your engines a/f ratio to accommodate the extra fuel or your engine will bog down and loose power. Consequentially - one runs the risk of putting the engine into heat stress if the supply of methanol is suddenly interrupted. Injecting water does not affect the a/f ratio. It appears that 50/50 mix has the best of both worlds.
In either cases, having a good w/a injection system with reliable "system fault" diagnostic capability is essential especially if you are running a high concentration of Methanol.