Hey all,

I was just curious why GM builds in a PE delay into some truck PCM's that makes them run super lean at full throttle. Quite a few trucks I tune will be at 16 to one A/F until I shut off the PE delay then they hit 13 to 1 or close to it nicely. The 6 liters pcik up 20 RWHP just by deleting the PE delay with no other changes.

 

The delay might be programmed in there to try and cushion the shock to the drivetrain. I supposed it revolves around trying to save the transmission.

 

I could see that but I would think the engine is more important than the transmission. Why are we all trying to stay so close to 13.1 tuning N/A cars if GM is running them at 16.5 to 1 from stock? I can't believe these things are not burning out valves and pistons at that A/F.

 

BTW, it is a 60 second delay so it basically is meant to never let the truck go into PE mode.

 

I never have figured out a reason for it and
killing it seems to help trucks a whole lot.
Better than trying to sprint whilst gargling.

 

Does anybody have any idea what the effect on engine longevity would be on an engine running so lean under WOT? They must have a reason for doing it this way at Gm, I just can't understand why.

I wonder if an LS1 in a F-body or vette would last under these A/F's. It obviously would not be the best for power but in theory?