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Aircooled engine going to methanol

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Hi guys. Its not a car. But it is an engine. Ive got a harley engine in a ducati frame circuit racer. Been running 100 octane leaded avgas so far. My issue is engine temp. Rear head temp gets upto 233 celcius / 450 f. Im going to swap to methanol for the cooling effect. Any idea what sort of temp drop could be expected on an air cooled engine? What sort of exhaust gas temp should i be aiming for when tuning? Its fuel injected. Naturally aspirated. Any info would be greatly appreciated

I'm not sure on your system that you are running on the bike, but temp change will be based on how hard you run it.. I was seeing 1150-1200F EGT in my drag bike with spikes to 1300F at the end of the 1/4 mile. The probe was about an inch away from the flange. My bike was air/oil cooled (1990 gsxr1100).

FWIW: Haltech has a meth wideband that puts out 0-5v and my MaxxECU can read it as standard o2 readings.

Im using the factory ecm with harley pro tuner program. A pretty basic ecm reflash & data recorder. It does not have provision for a egt input. Im going to have to use a separate sensor / gauge. Im happy to keep using this tuner as the bikes setup is pretty simple with no launch control. Turbo. Etc. Want to keep bike weight complication to the minimum so egt would be use & remove. Any suggestions on brands available in NZ

The other question is what is a safe maximum engine temp for an air cooled 4 stroke engine???

Might be worth taking a look at flat rack forums? I know a lot of those guys run methanol.

I cant answer the methanol specific question, but can give some info on Cyl head temp. The Harley heads are made from a common aluminium alloy known as A356 and heat treated to T6 condition. The T6 properties will start to deteriorate from about 165°C. The higher you go above the aging temp the faster the over-aging happens. The original design intent would have been to keep the cyl head below 165°C at all times. Depending on how accurate your CHT sensor is and where it is placed , if 230°C was the general bulk temp I would estimate you are now probably already down to less than half its original strength. As the metal loses strength you will typically start to see the areas under the washers/bolts mushroom out and the head gasket sink into the aluminium and valve seats start to move around or come loose.

I would suggest getting the heads hardness tested to see how affected they are. Original hardness would be around 120HB, typically anything less than about 80HB wont work well on a performance engine.