Another Subaru mapper (Andy Forest) says:IIRC, methanol is about 50% oxygen by weight. So if you add 10% by weight to the fuel you're running you'de have 5% by weight oxygen. All things being equal you might expect to see another 5% power, but of course if you're knock limited to start with, the octane number improvement from the methanol will permit you to run closer to MBT and thus improve thermal efficiency, thus realising >5% increase in power.
It seems to be used regularly by top uk subaru tuners:I have found that adding up to 10% methanol will increase power, improve the safety threshhold to detonation and have zero effect on EGT.
It primarily depends on how lean the car has been mapped on petrol as to how well it responds to a methanol mix. If its on the edge with petrol it will not like the additional leaning out experienced when adding methanol.
If Bob mapped your car then he knows your set up and you are right to follow his advice in this case.
Generally any std factory map car or any of the cars I have mapped will make immediate and safe gains by adding 10% methanol. Specific remapping will pull another few bhp but then you are resigned to continuous use of that mix.
Bob Rawle
Paul Blamire from Zen Performance
Andy Forest
Simon (aka Jolly Green Monster)
Zak @ Mocom
All adding around 10% mix to the tank before filling up or 1 gallon to make it easy. This is for track or drag use rather than everyday use afaik
:)