Quick question about a/f's

[Supra0089]

Hey everyone. Right now as my build sits, under WOT the car, according to my aem wideband and a/f gauge, starts at about 11.5 and then slowly drops down to 10 (minimum reading level on gauge) as it approaches 16psi. Is this normal for not having a tuning device? I've leaned out the fpr a little (30 to 28) and it doesn't seem to help much. I'm not going to mess with it anymore cause I'm afraid of blowing something up until i get on a dyno and have a turning device. My buddy at the performance shop I work with is saying that the computer is responding to the afm and compensating for the air flow by creating more rich conditions. Thoughts? Opinions?

Here is my setup:
50 trim ct
FMIC and piping upgrade
aermotive afpr
aem wideband
lex afm w/ screw out
walbro 255
550cc's
3" turbo back exhaust
intake
boost controller set for peak psi at 16
other gauges
new motor/head w/ hks 2mm metal HG

Another side question, I'm shooting for 350whp. Is this doable with my current setup with a tuning device and a good tune?

 

[Nick M]

Hey everyone. Right now as my build sits, under WOT the car, according to my aem wideband and a/f gauge, starts at about 11.5

During normal driving at operating temps? No, that isn't normal.

and then slowly drops down to 10 (minimum reading level on gauge) as it approaches 16psi.

That is normal.

My buddy at the performance shop I work with is saying that the computer is responding to the afm and compensating for the air flow by creating more rich conditions. Thoughts? Opinions?

The AFM doesn't respond to a rich condition. It measuers the volume of air entering the engine. Under boost, the volume is higher and faster, and the AFM shows this. The ECU then enrichens the mixture over the standard amount for engine speed and normal load. The oxygen sensor is what compensates for conditions in closed loop. If you are running 11:1 in closed loop under a normal load, you might have an exhaust leak creating a false lean signal.

 

[Supra0089]

Sorry wasn't clear. Normal load is 15-16 af, WOT is 11.5.

Thanks for clearing up the dropping to 10 as normal. Makes me feel a little better.

 

[CajunKenny]

My recommendation is to back your boost down to 14 psi until you can tune.

Trying to "Tune" by adjusting your fuel pressure is just silly.

Set it back to the TSRM spec and let your FPR do it's job.

 

[Nick M]

You should not be lean, unless you have pulled fuel with a pressure regulator. The further out the bypass screw on the AFM is, the less air the ECU thinks you are getting, and the less fuel it will deliver.

 

[Supra0089]

Thanks for the suggestions. Makes sense.