Quote:
Originally Posted by pbonsalb
You are just adding octane for consistency unless the tune is designed to be flexible (Carbahn claims its tune will adapt). How you add a little octane is up to you. Race gas is a waste in my opinion since it has about $10 per gallon. Mixing in some E85 is the way to go if it is readily available in your area. Even a stock tune can handle a little E85.
If you really want to add more performance through octane, you need a tune for that octane. Otherwise it is just a safety device to ensure the tune performs as expected. Most tunes are conservative to start with.
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Hmmm. From what I have seen, tunes use up the timing and boost buffer BMW leaves in, therefore reducing safety margins BMW purposely left in. I believe the F90's DME is better at handling and correcting tune issues (read: pull timing) before catastrophic engine failure occurs then the F10 M5 did but IMHO I think it's still wise to run at least 93aki on any tuned turbocharged BMW. Safety margin aside, It nearly always results in a net performance increase in my experience. 95ish seems to be the sweet spot, anymore is usually a waste of money unless it's a stage 3 type tune and pushing turbo effectiveness to the ragged edge.