[hardk0re]

Alright, now my car was running real nice at one time (1 week ago)....idle/cruse was a 14.7 A/F or there about, and at WOT it was pretty much bang on at 12 A/F.

Now this was when I was running Sunoco 94, now given gas prices I switched it up and started using Shell VPower 91, now I'm noticing that at idle/cruse it still seems to be 14.7 but at WOT it starts off at 12 A/F and then near the top of the gear drops off the charts (below 11 A/F)....


Now when I was running Sunoco 94 I was finding my A/F lean so I got Randy to add fuel. With 94 it was running 13's and then randy brought me down to 12's and now with 91 i'm running 11's.

I guess what i'm asking is would the 94 be causing it to run leaner than the 91, or would the 91 simply not be burning well and showing a rich condition?????

Has this happened to anybody on here? (limited FI base here but maybe its something weird with our cars...???)

[darkpuppet]

Sunoco has ethanol in it, which runs leaner than non-ethanol brands... so yeah, switch to regular gas and your a/f may get skewed when you go into openloop.

I also know from reading around that ethanol produces less power per volume than gas, so I wonder if the knock-reduction properties of the higher octane would offset the power loss with the addition of ethanol... I tend to tune for 91 regular..

[edit]I also know (especially from r/c racing) that alcohol tends to love bonding with water, and has an increased tendancy to do so and separate from the gasoline as temperatures decrease. Yet, i'm sure that they put alcohol in the tank to act as a gas line antifreeze? I honestly don't know what explains this paradox..[/edit]

[darkpuppet]

another side note...

I originally tuned with 94 sunoco, but on a borderline tune, I found that when I switched to regular gas, it would throw the fuel trim corrections into the wall, and caused some issues with me... a properly tuned MAF transfer function would avoid this of course (only took me a year to get it right).