924Board.org

AFRICA DEE

Question 1, If one normally run your 1980 931 on 95 unleaded and the tank has 20 liters left and you fill up with an extra 20 liters of 102.6 octane , do you get an average octane rating of 98.8??
Question 2, with FMIC but standard timing set up running normally on 95 octane, and one wants to now and again use 102.6 octane for a track day, do you have to alter any timing settings etc. Are there other things to worry about when you alter/mix between fuels??
_________________
1980 924 N/A Ex-931 Track car: My cash guzzler
2004 996 4S: My Weekend plaything
2012 VW POLO GT: My daily commuter

Peter_in_AU · Joined: 29 Jul 2001 Posts: 2743 Location: Sydney, Australia

Not a chemist. Your timing advance should be increased for higher octane fuel. Two reasons; first because you can and second because higher octane fuel burns slower than lower octane fuel.
_________________
1979 924 (Gone to a better place)
1974 Lotus 7 S4 "Big Valve" Twin-cam (waiting)
1982 924 (As featured on Wikipedia)

Learn to love your multimeter and may the search be with you