I have an 06 MR, has been dyno tuned by Buchur on 93 octane fuel. My question is since it was tuned on 93 will performance be affected at all if I run 101 or even 110 octane on the track? Is the tune now a solid state that will not change? Or will the engine continue to advance timing as far as the higher octane fuel will allow? Im planning on racing quite a bit this year and figured higher octane is at least safer for running it hard for a day straight but Im just not sure how much performance will be affected if any at all

 

No, your performance should not change with increased octane. As long as it was tuned right for the octane you normally run, it shouldn't be running in the lower octane maps, so you shouldn't see a difference in performance and timing. The ECU does not just add more timing.
Once a car is right and the tune is right, it's set. Running the higher octance will only be safer or allow you to change parameters that will increase performance; more boost, more timing.

 

Thats what i was thinking but wasnt sure. Thanks for the reply

 

your tune would definitely need to be changed if youre going to be running 100-110oct fuel. the race gas will richen your afr by a lot and you will make your car slower just by running that fuel without a tune for that octane.

 

Running a higher octane fuel raises AFR? Please explain or elaborate.

 

I dont know the reasoning behind it but if you go fill your tank up with 100oct your aif fuel ratio will probably go from an 11.5 down to 10.7-11.1 probably, atleast that is how my car reacted to the fuel. When I tuned my car with the 100oct my fuel map had to be leaned out almost a full 1.0 and increased the timing a several degrees

 

Hmmm? The only thing I can think of that causes shifts like that would be the ECU going back and forth between between high and low fuel maps. The car is pretty much constant unless there's something mechanical. I keep my fuel maps the same, keep different high and low octane timing maps for safety, and tune very conservatively. I kinda though most tunes were like this. What do your fuel maps look like? When you log your car what octane percentage is showing?
b18c5crx you might just have to log your car and see what goes on then.

 

the car is not jumping back and forth inbetween high and low octane because the car isnt knocking. when i run race gas its a mix of 5 gallons 110 leaded with 7 gallons of 93 unleaded. my a/f ratio is pretty much a flat 11.7 from 3500-7000 on the wideband