It takes like 7 miles of driving after a fillup for the computer to figure out the alcohol % and adjust to the higher octane tune tables.
Did you have a custom tune done or just using stock? If custom, did they do anything to the E85 spark tables?
Sent from my SM-G930V using Tapatalk
Right. I just cruised after filling up on I-10 for eight miles before commencing any "testing".
I do have a custom tune for the cam and raised compression. I had it tuned on 93. My thought, since E85 is nowhere nearly as available as 93, was to have it tuned to the max on 93 and let the PCM advance it from there when it detects the elevated alcohol content. I went this route since the actual net alcohol content varies wildly (or so I've read) from source to source. Had I tuned it to the max on E85 (or whatever % I netted), it'd retard the timing should I get a lower % of alcohol, including running E10 with 93. Also, it adjusts for time elapsed between refueling events due to fuel losing it's octane rating as it ages. My Tahoe sits a LOT and I usually fill up once every month or two. All considered, the amount of available power is more stable, I have a reduced chance of detonation, I'm really not sacrificing a whole lot of power at all, if any and I still have the convenience of running 93 if E85 isn't within range.
...I am kinda tempted to get my own tuning program and playing/learning, though.
