higher octane fuel runs leaner??
 

Tuned a few cars today, but only 1 ran 101 octane.

I initially tuned him on 8psi on normal 92 octane pump gas. The car ran great, no misfires, no detonation, plugs looked sweet and had AFR's go from 12's down to 11.7 at WOT redline(6.5k).

He decided he wanted to run 101 octane because he just wanted to take extra precautions and wanted to run a bit more timing and up the boost to 11psi.

Well, we fill up and the AFR readings turned almost an entire point leaner. I'm really lost as to how that happens. :S It was a long ass weekend, so it might be an easy answer but it's just not hitting me right now. :-[

Tuned it out tho. It's an EF hatch with a stock f22a1. 60 trim t3/t4(too big for the engine and psi he's running, imo), ran a best of 14.3 at SIR. Had a horrible 60'(2.4) and couldn't really hook up. He'll be making some tractions bars for it soon. :y

Re: higher octane fuel runs leaner??
 

higher octane fuels if anything would read richer.

Re: higher octane fuel runs leaner??
 

That's exactly what I've learned with all my experience and reading.... This one really ------- stumped me.

Spiker, where were you this weekend? I was expecting you to be at the track nig