Commanded AFR leaning out in PE

[skalor]

I've been tuning my friend's turbo 4.8 2010 Silverado and I've come across something weird that I can't figure out. Sometimes while in PE the commanded AFR will go from the 11.29 that I'm commanding via the PE EQ table to a 12.24. It happens at frame 15,500 in the attached log. I'm thinking it must be time related because it only seems to do it on longer runs. Right now I have the AFR spark table set to start taking timing out a 11.7 so that when it goes lean it doesn't see knock but I want to correct this so I can up the timing again without having to worry about it.

[IDRIVEAG8GT]

Fuel Pressure? I think that it is reaching the limits of the fuel system. Is the boost spiking in that area? I would max out the fuel pump since your DC max is at 90%

[skalor]

IDC is only at like 63%(14 msec) so I don't think there's anything wrong with the fuel system. It has 80 lb injectors and dual 255s in tank for reference. Besides, if it was the fuel system I would think it would still maintain the same commanded AFR. What happens is that the commanded AFR actually leans out to a 12.24.

[IDRIVEAG8GT]

Wow never mind that suggestion then :O let me check back through your tune. Could be a Commanded AFR error.... If I see nothing wrong I'll ask one of the Geniuses on this forum. for Geniuses.

[skalor]

No one knows why the commanded AFR is changing while in PE?? Here's a screen cap of it happening. The commanded PE AFR is set to 11.29 from 3000 to 8000 rpm.

[Chris@HPTuners]

it is most likely the LTFT Purge Reduction Factor, i can't remember if you set it to 1.0 or 0.0 across the board and it should fix it.