Here are some comments about the various alcohols by John Estill and Carl Ijames..both of whom know what they are talking about when it comes to such things.
John Estill's calcs:
Water injection: 0.40 lb/min of water will vaporize, cooling the air down from 150 F to 109 F.
100%: 1.08 lb/min of methanol will vaporize, cooling the air from 150 F to 96 F.
50%: 0.55 lb/min of methanol/water will vaporize, cooling the air from 150 F to 107 F
100%: 1.26 lb/min of ethanol will vaporize, cooling the air from 150 F to 100 F.
50%: 0.57 lb/min of ethanol/water will vaporize, cooling the air from 150 F to 108 F
70%: 0.76 lb/min of alcohol will vaporize, cooling the air from 150 F to 107 F.
91%: 1.14 lb/min of alcohol will vaporize, cooling the air from 150 F to 104 F.
100: 1.50 lb/min of alcohol will vaporize, cooling the air from 150 F to 102 F.
From the above, I gather that methanol actually works better than water when it comes to cooling due to its lower vaporization pressure even tho water when it boils releases more heat. I may be wrong as I am not a chemist.
Alcohol is an oxygenated fuel, not an oxygenator like nitrous. Nitrous
absorbs heat as it vaporizes, cooling the intake charge, and also
decomposes to release nitrogen (basically inert) and oxygen gases. This
oxygen can then react with extra fuel and thus release more energy than was
consumed in the decomposition step. Also, the bulk of the nitrous enters
the combustion chamber as a liquid before it vaporizes and decomposes,
which acts like a supercharger - it increases the total oxygen in the
cylinder above what would normally be drawn in.
Alcohol, on the other hand, can be viewed as a partially burnt hydrocarbon.
It does not release free oxygen gas in the combustion chamber, and because
some carbon-oxygen and oxygen-hydrogen bonds have already been formed,
fewer will be formed during combustion and so less energy will be released
(skipping a few chemical details ). That lower energy (heat of
combustion is about half that of gasoline) is why oxygenated fuels give
lower gas mileage - 2 to 4 mpg less on my car. Alcohols do have much
higher heats of vaporization than hydrocarbons which means they will cool
the intake charge better. For comparison, hydrocarbons are about 70-80,
methanol is 262, ethanol is 204, isopropanol is 159, water is 560, and
nitrous oxide about 40, so methanol absorbs about 3.5 times more heat than
gasoline as it vaporizes. Also, the alcohols have high octane ratings,
about 98 (R+M)/2, and wider flammability limits than gasoline which
probably gives more complete combustion. My guess as to why you can go
faster without turning up the boost is that you were slightly too rich
before to suppress detonation (and were probably still getting a little
timing retard). The octane boost and charge cooling let you lean it out
some and keep the timing a little more advanced to make more power and
still be safe.