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Old 12-02-2005, 08:26 PM
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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.
Old 12-03-2005, 03:22 PM
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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.
Old 12-03-2005, 05:19 PM
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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.
Old 12-03-2005, 05:20 PM
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BTW, it is a 60 second delay so it basically is meant to never let the truck go into PE mode.
Old 12-03-2005, 07:55 PM
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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.
Old 12-04-2005, 06:13 PM
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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?




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