GT Bob

On an NA car, 12.8 is fine. I've set countless customers in that area and it's always been good, and the 2 GT's I tuned seemed to like that general area as well. 12.3 is about as rich as I have ever gone on an NA car (and that was a 11.5:1 compression LS2 with enough cam for 2 cars...), and 13.2 was the leanest. Once you add forced induction or a dedicated Nitrous tune, thats when you start going into the richer mixtures (below 12:1). Generally, I stay in the 11.5 to 11.9 range with forced induction, unless the setup or conditions demands a richer mixture.

The reason you go richer in the FI and nitrous tunes is because of the higher cylinder pressures. The higher the cylinder pressure, the more likely detonation is to occur. To keep from having to pull extra timing (because timing makes more power than AFR usually), you throw more fuel at it, to cool the charge and slow combustion and leave the timing alone. Since in an NA car, this isn't an issue as much, you can leave it leaner.

There is a point where less timing and less fuel works better as well, but thats why a good tuner is worth his weight in gold. He'll be able to figure that out pretty quickly and set ya up. Tuning isn't as simple as setting an AFR and calling it Miller Time. There are countless things in the tune that you can change that will have a multitude of effects. Less fuel, more timing may give ya top end, while more fuel and less timing may help your bottom end, and on the next car you tune, it will be a completely different ballgame.If you had your car tuned professionally, then I would say leave it alone. Chances are that this guy, who does this for a living, will have it set up alot closer to where it needs to be (he does have a dyno to help after all) than you will be able to get it with your ever so finely calibrated Seat-o-the-pants-o-meter.

GT John

Since your running N/A anywhere betwen 12.8 and 13.2 at WOT is good. Mine dyno'd out at 12.8.

S/C's are generally set at 11.8.

mac10chap

thanks guys...i just wanted to see if there was any way i could safely draw more HP out of my car just by adjusting the A/F ratio. I guess i am just gonna have to go buy the ZEX kit and delete plates now.