Let me clear up a few misconceptions y'all seem to have, as far as fuel is concerned.
Alcohol is often used in high performance engines, NOT because it burns hotter or contains more energy, but because it requires less air to achieve the proper stoichiometric ratio. Gasoline engines require 14.7 parts air to 1 part gas. Methanol engines run 6.42:1. So what does this mean? Although gasoline actually contains more energy than methanol, methanol requires less air to burn, and so we can cram a whole lot more methanol in the combustion chamber.
This site sums it up pretty well.
Now, about testing your methanol engine with 93 (or any other octane gasoline). DON'T! You're dumping nearly 3 times the amount of fuel into the combustion chamber that's needed. It wastes fuel, leads to increased carbon build up, and can damage piston rings if run that way for too long. Methanol also burns much slower than gasoline, and as a result, methanol engines run more spark advance.
Also, read one of my previous posts about octane ratings:
Not this again...
OCTANE is a rating which describes the temperature at which a substance ignites. There are several rating systems, but here in the states, we use the Anti-Knock Index (AKI). The OCTANE rating has ABSOLUTELY NOTHING to do with the energy content of the fuel.
If you don't believe me, let's look at an example:
Regular (87) unleaded has an octane rating of 87 on the AKI scale. One gallon of this fuel contains 114,000 BTU.
Pure ethanol has an octane rating of 99.15 on the AKI scale. Although the octane rating is higher, one gallon of ethanol only contains 76,100 BTU.
Converting an known alky carb back to gas forget it. B&S flatties that are setup to run alky, theres more to it than a jet change in the carb. Carbs setup to run alky have the cat eyes behind the jet opened up and a different size jet. Therefore when trying to run gas you are dumping way to much fuel for the engine to run correctly. If you want to run gas, best to change to a carb. that is kown to have to run gas. Best way I have found to check if it is a alky carb, pull the needle valve and the jet and look down in the hole and look at the cat eyes. Gas carb, one small cat eye and one large cat eye. Alky carb to large cat eyes. Or compare a known gas carb cat eyes dia. agaisnt a carb that you think has been run on alky.
