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Thread: Went to a 2 bar, now the trans line pressure is maxxed out

  1. #1
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    Default Went to a 2 bar, now the trans line pressure is maxxed out

    As the title states, I went 2 bar because of the blower on my 1500 I just installed and now every gear snaps your neck (part throttle and WOT alike). It's going to snap hard parts too if I don't figure out what's wrong. What do I need to capture to figure this out? There are no large vacuum leaks that I can see and the MAF is plugged in in its original home (Whipple) so no changes to its characteristics. Still has the screen too.
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

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    And after dropping the IFR from around 4.9 to 4.5 the truck is happier, AFRs are better, response is better, LTFTs are much closer to where they were before the swap, and now the trans shifts normal? Was it the IFR change, did the MAF decide to play ball, or was it me finally getting the blower bypass valve vacuum line situation right? Either way the truck is awesome now! Just need to give it a calc.vet so I can unrape the PE. Only seeing small amounts of KR on the initial guesstimated tune, I'm very pleased with how it's turning out so far though I am ready to pulley down now.
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

  3. #3
    Joe (Moderator) joecar's Avatar
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    Post your before and after tune files and any logs (identify them as from which tune they came from).

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    There are max pressure enablers in the transmission segment that have to be disabled. Might want to confirm they are done. It should be the custom os tutorial.
    00 Silverado Z71, LQ9 w/ LS3 heads, BTR cam, Whipple 2.9@8#, 4l80E

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    I don't remember the max pressure enablers being in that COS tutorial but that doesn't mean I missed them. I should say I'm not MAFless. Here are the tunes and logs. I know I'm way off, it seems to pull a lot at low load and less at higher loads. Odd. Tune 1 goes with log 1 and tune 2 goes with tune 2. I still have the calc.vet parameters loaded but can't do one until I settle on an IFR. Problem is, when I set the IFR correctly the truck has such a terrible tip in off idle it's basically undriveable. Once off idle, tip in is fine. I can watch the wideband go full lean when I poke it from a stop, I'm totally lost on that one.

    411 Whipple V1.tun
    411 Whipple V2 IFR Change.tun
    Whipple Log 1.efi
    Whipple Log 2.efi
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

  6. #6
    Joe (Moderator) joecar's Avatar
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    Are you seeing any DTC's...?

  7. #7
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    Just the evap and something else that isn't hooked up.
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

  8. #8
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    I guess I'm not worried so much about the trans now that it only did it that one run. I'm now far more concerned with how to kill this off idle lean spot I have because it prevents me from settling on an IFR which prevents me from running a calc.vet, going after the timing, and tweaking the IAT as I suspect I'll need to let it pull timing more aggressively.
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

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