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higher octane does not burn nore complete, thats why it often burns cooler (the rich mixture I was talking about)
I you have a bike that was set up perfectly for racing on 87 octane, dyno tested and EGT dialed in and all the spark plugs carefully tested and have the same light tan coloring.. the run that same engine on race fuel... oxygen sensors will show a rich condition, EGT temps will drop way down and the plugs will be much darker.
The reason is because the fuels with the higher flash point and additives in the fuel that prevent detonation/knock have slightly slower flame fronts making it harder to burn the fuel... thats why you need the higher compression.
if you want to see the difference its simple....
dyno your bike
run it hot on 87, then drain the tank and carbs and run it again on 93+ or race fuel.
With the same jetting you will lose power.. THAT'S FACT.
An efi bike or car it won't make as much difference as the fuel delivery and timing will be adjusted on the fly to compensate for the extra rich mixture picked up the the oxygen sensor.
I have had many race bikes dyno tested and EGT?CHT dialed in. this allows me to show the owner and myself what fuel is needed to run the best and prevent detonation. I prefer using the EGT/CHT's and reading plugs on smaller engines or air cooled because I can watch whats going on. If the EGT's drop but CHT spike I know that its detonating even if I can't feel/hear it. if EGT and CHT are low I know I need to lean it out etc etc Once I get the bike set withing a decent heat range with the EGT then I start plug testing to see if its safe to lean it out anymore. Once I have the jetting dialed in perfectly reading plugs (the ONLY way to properly dial in jetting) then I can use the EGT/CHT to monitor the engine.
I you have a bike that was set up perfectly for racing on 87 octane, dyno tested and EGT dialed in and all the spark plugs carefully tested and have the same light tan coloring.. the run that same engine on race fuel... oxygen sensors will show a rich condition, EGT temps will drop way down and the plugs will be much darker.
The reason is because the fuels with the higher flash point and additives in the fuel that prevent detonation/knock have slightly slower flame fronts making it harder to burn the fuel... thats why you need the higher compression.
if you want to see the difference its simple....
dyno your bike
run it hot on 87, then drain the tank and carbs and run it again on 93+ or race fuel.
With the same jetting you will lose power.. THAT'S FACT.
An efi bike or car it won't make as much difference as the fuel delivery and timing will be adjusted on the fly to compensate for the extra rich mixture picked up the the oxygen sensor.
I have had many race bikes dyno tested and EGT?CHT dialed in. this allows me to show the owner and myself what fuel is needed to run the best and prevent detonation. I prefer using the EGT/CHT's and reading plugs on smaller engines or air cooled because I can watch whats going on. If the EGT's drop but CHT spike I know that its detonating even if I can't feel/hear it. if EGT and CHT are low I know I need to lean it out etc etc Once I get the bike set withing a decent heat range with the EGT then I start plug testing to see if its safe to lean it out anymore. Once I have the jetting dialed in perfectly reading plugs (the ONLY way to properly dial in jetting) then I can use the EGT/CHT to monitor the engine.
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