I am running a Comptech SC that is tuned with a VAFC (... I know) on an otherwise stock S. This is a weekend car that sees spirited runs and an occasional track day (I'd add/mix higher-octane fuel on track days).

This week I stumbled into a conversation about my a/f ratio with a respectable local tuner. When he looked at my a/f graph he immediately said, "That's too high! Don't push the car, you really need to lower the ratio."

This is my graph (the colors may be hard to discern; look at the line at starts at 13.8 AFR that declines, not the line that starts at 14.2):


What I have difficulty gauging is: How concerned I should be?

I don't have a good sense as to whether I need to take immediate action because I'm driving a ticking bomb, or to just note that it is running a bit lean and to retune or to upgrade the VAFC at my leisure. I'd appeciate your constructive comments and suggestions.

TIA.

Oh, and yes... he did advise me to ditch the VAFC.

 

I agree with your tuner completely. You're running dangerously lean.
fltsfshr

 

Thanks fltsfshr.

I keep going back to this thread for reference: When is LEAN TOO LEAN? AFR

It seems that 13:1 is the target range for FI cars which makes me wonder why my VAFC tuner felt comfortable with my afr graph. At higher RPMs where lean fuel can be most damaging my afr is kinda sorta safe?

 

You should have UL tune your car. 13.5 is a good aim for NA cars, but the number should be lower (richer) for SC cars.

 

yes you should be between 12.1 and 12.5 to run safe. You're actually running lean all the way across. Tough on your motor.

fltsfshr

Only way I could get that kind of fuel curve was to go to an aem ecu.

 

[QUOTE]Originally posted by spider
You should have UL tune your car.

 

[QUOTE]Originally posted by Hitman

 

I would actually try not to go over even 12.2 for the A/F (WOT). I noticed in my car I'll get knock even at 12.3.

Honestly, when I'm WOT, my A/F parks at 11.0. I feel much more comfortable there. I would definitely baby your car around until you can get that changed.

Dave

 

[QUOTE]Originally posted by bgbfflochp
I would actually try not to go over even 12.2 for the A/F (WOT).

 

[QUOTE]Originally posted by kane.s2k