Strange fuel cut at 8 psi
 

Hey guys. I'm stumped trying to figure out what just feels like fuel cut symptoms.

If I'm WOT, car revs fine up until load is about 8 psi then the afr spikes up for no apparent reason as if there was some sort of fuel or boost cut.

Now, I'm new to the microtech, just going through the manual and doing a coarse tune on my car.
The car has LT-10s ecu with the X4, single BorgWarner T3 turbo, aeromotive fuel pump and fpr, 4x 550cc secondary injectors, cant tell what the primaries are.

Car starts, idles, revs great.
In neutral the car will rev happily to redline.
Under light throttle, the same will happen.
However under heavy throttle, hitting 8 psi regardless of speed, will cause the problem.

My load map is smooth through the entire RPM range, I tried spiking fuel incrementally while driving, but it made no apparent change. Change the load map is not fixing this.

Is it grounds?
Is it my injectors?
Is it my fuel pump?
A leak?

I checked the BSTcut and it's set to 22 psi. Previous owner said it was running 18 psi.

Any help or ideas would be greatly appreciated.

Can you monitor fuel pressure? What happens at that point?

Does anything change in the status display on the Microtech when this happens? Like going from "RUN" to something else?

Always at exactly 8 PSI?

As an experiment, set the boost cut to 4 PSI and see if the issue now moves to 4 PSI.

Thanks for the reply Aaron.
Before I saw your post, I set the dialed the boost cut back while the car was idling to 15'' which is was the idle vacuum was and it immediately killed the car, so I don't think that is the same thing I was experiencing. I set BSTcut OFF after that.

My timing map was kinda flat after 6 psi, so I fixed that and that was making me go lean before, but I'm still having the exact same issue at about 8 psi. BUT I CAN see my AFR now and it is staying rich. Right about 10.5-11 and the just starts bogging/hesitating, and wont build anymore boost. AFR stays right where it should, which makes me think fuel pressure is fine yes?

What else should I check within the ecu? or is this some kind of other problem? like a coupling flexing apart at 8 psi and then holding fine under that lol

I didn't look at the status display, I can check that next time I'm in the car.
And yes, it is always right about 7.5-8 psi

Even at 0 degrees of timing, the AFRs shouldn't show lean.

Have you checked fuel pressure? Remember, a wideband doesn't read air fuel level, it reads exhaust oxygen content. Misfires will cause it to read wrong.