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Thread: gmpp lt4 e92 no boost/not opening throttle

  1. #1
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    gmpp lt4 e92 no boost/not opening throttle

    hoping someone can help me out with this lt4 swapped chevelle- It will not go over 45% actual throttle so it never shuts the bypass valve and never makes any boost. It does it with the stock gmpp file as read, and I havent been able to improve it with any driver demand increases. I've attached a log and the file, it doesn't exceed axle torque requested it's actually inverse of that. I'm wondering if its trans related- I've tried mapped gear as 0,1,2, etc- It is a TKX with no feedback and I've also shutoff vss torque to rule that out. I've lowered PE to make sure it's in early and tried it with and without a clutch switch. There has to be something I'm missing- Any help is appreciated.
    Should note there's some oddball stuff in the file like idle torque maxed at 830 and max torque at 6040 across the board- this was as shipped from gmpp, though I have tried actual tables from a pulley only zl1 I did last year and it didn't make a lick of a difference.
    Also- don't mind the ridiculous amount of PIDs in the log, I just started adding anything and everything map/tps/torque related looking for a discrepancy.
    Attached Files Attached Files

  2. #2
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    Take a look at your dtc's.
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

    ~Greg Huggins~
    Remote Tuning Available at gh[email protected]
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  3. #3
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    Quote Originally Posted by GHuggins View Post
    Take a look at your dtc's.
    Thank you, not throwing any though. The GMPP file has a ridiculous amount of them set to no error reported. I actually re-enabled a bunch just to find a misfire that was a mis-pinned injector high voltage signal. Maybe I ought to reenable the rest. I may have answered my own question in the meantime though- the gmpp manual explicitly states it needs a 40 pulse per revolution vss or it'll limit the throttle. The tkx is 17 pulse, I'll find out tomorrow if the pulse correction fixes it. I cant find anywhere in the file that connects the two though so we'll see.

  4. #4
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    This is from the log you posted. No fuel control/correction, both pre-cat o2's non operational and throwing boost control codes. These should pass and not show permanent if everything was operational. I can tell you from experience if an lt4 doesn't have fuel control or see's any sort of fueling issues they will try to limit boost and yes it needs the vss input although there are OS's that can work around that.

    Posted lt4 log.jpg
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

    ~Greg Huggins~
    Remote Tuning Available at gh[email protected]
    Mobile Tuning Available for North Georgia and WNC

  5. #5
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    Quote Originally Posted by GHuggins View Post
    This is from the log you posted. No fuel control/correction, both pre-cat o2's non operational and throwing boost control codes. These should pass and not show permanent if everything was operational. I can tell you from experience if an lt4 doesn't have fuel control or see's any sort of fueling issues they will try to limit boost and yes it needs the vss input although there are OS's that can work around that.

    Posted lt4 log.jpg
    Thank you. I should have have clarified it doesnt have any DTCs that are relevant currently, it doesn't have a bypass valve solenoid (it's a gmpp crate setup they just get a vacuum line to the port under the TB and a foam filter over the vent), and it's single bank in this log with bank 1 set to 0's in both heater and general tables, and feedback is single.....my wideband is in bank 1. I usually tune them this way since I street tune and these need VVE done first so I dont have to keep putting it back in the air to pull my sensor out, I can just pull the negative sign off the readiness voltage and go back at the maf curve with trims off one bank and that usually gets me close enough.
    I will try putting the bank 1 sensor back in the loop and see if the vss doesnt solve it but this issue is why I have the car in the first place. It showed up with the problem with both o2's and everything as it was shipped from summit.
    I get they're sensitive but I've never had one not make boost in open loop though I have seen a few threads about them being picky in SD.
    Thanks for your time in looking the log over, your responses on here are paramount. Think this is the first gen v issue I've had that you havent solved for someone else yet. Can usually find what I need in a ghuggins reply somewhere!

  6. #6
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    Well it?s sorted out, vss wasn?t the culprit it was the lack of a bypass valve- needed to disable it under torque management, sc/tc. suspect it was supposed to be disabled as confirmed from another gmpp lt4 file i found here on the forum, just got missed with whoever set up this e92 before it was shipped.

  7. #7
    Quote Originally Posted by wicked_z71 View Post
    Well it?s sorted out, vss wasn?t the culprit it was the lack of a bypass valve- needed to disable it under torque management, sc/tc. suspect it was supposed to be disabled as confirmed from another gmpp lt4 file i found here on the forum, just got missed with whoever set up this e92 before it was shipped.
    There are 3 Chevrolet Performance calibrations
    The 1st one was for the older engines with the 4 wire analog fuel rail pressure sensor 2015-2017 I think
    The 2nd is for the 3 wire digital fuel rail pressure sensor 2018-2021
    The 3rd is for the 2022+ VVT valve change and removal of the bypass valve on the supercharger. I was told by GM if the incorrect controller was used on the newer engine it will kill the VVT actuator over a shorter amount of time.
    2009 Maverick Silver G8 GXP M6 - 586hp
    Engine Mods: TVS 2300 Magnacharger ARH 1 7/8" long tubes with catted x-pipe
    Drivetrain Mods: Ram Dual Disc Clutch
    Suspension Mods: Pedders/Wretched basic drag pack - BMR trailing arms
    Misc Mods: Jamesbiz Catch can - GRRRR8 Heater hose relo kit

  8. #8
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    Quote Originally Posted by radrace19 View Post
    There are 3 Chevrolet Performance calibrations
    The 1st one was for the older engines with the 4 wire analog fuel rail pressure sensor 2015-2017 I think
    The 2nd is for the 3 wire digital fuel rail pressure sensor 2018-2021
    The 3rd is for the 2022+ VVT valve change and removal of the bypass valve on the supercharger. I was told by GM if the incorrect controller was used on the newer engine it will kill the VVT actuator over a shorter amount of time.
    Any chance you could post all 3?

    Is the bypass disable switch only in newer hpt versions or something. I don't see the switch - only settings to ignore it. Unless the earlier years didn't have it in hpt. I think that's the issue with the one I'm looking at right now. Ok..... Doesn't have the supercharger tab, so more than likely
    Last edited by GHuggins; 12-03-2024 at 07:38 PM.
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

    ~Greg Huggins~
    Remote Tuning Available at gh[email protected]
    Mobile Tuning Available for North Georgia and WNC