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Thread: LFX not going WOT until 4300 RPM

  1. #1
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    LFX not going WOT until 4300 RPM

    I can't find this information anywhere.

    My 2013 Impala with LFX V6 will not open the throttle blade to 100% until about 4300 RPM. It is bone stock mechanically. How do I remedy this in the tune? Do I have to modify virtual torque tables? I believe the engine torque is being limited by a table I don't have access to. It bogs really bad on launch until I hit right around that 4000 RPM mark.

  2. #2
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    How much is it opening? People will want you to post a tune and log so they can see it.

  3. #3
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    Apparently this is a known issue on these cars which is why I didn't post my particular tune, but here it is. It's not really dialed in at all because I've been trying to fix this throttle issue before I work on any fine-tuning. I've also attached a log. With pedal at 100% from a stop the commanded throttle actuator only starts at about 75% and then slowly ramps in to 100%.
    Attached Files Attached Files

  4. #4
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    No external throttle controller. I'm saying when I push the gas pedal 100% of the way down, the computer is only commanding the blade on the throttle body to open 75% at first.
    Last edited by derpyimp; 08-30-2020 at 12:47 PM.

  5. #5
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    Yes, my misunderstanding. So this V6 is bone stock and the tune is original as well?

  6. #6
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    The car is mechanically stock. The tune is not stock. I have disabled most torque management and made basic adjustments to the driver demand table to improve throttle feel. I've also modified the shifts a bit. But the throttle problem has been there through all of it.

  7. #7
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    I'm no pro, but I would flash the stock file in since the car is stock. If the problem persists, then you know it's a mechanical issue. Possible the TPS or TB is screwed up?
    Last edited by marksrig; 08-30-2020 at 01:58 PM.

  8. #8
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    It's not mechanical. This is a known issue in the stock tune on the 3.6 Impalas around this time. I believe it has something to do with the torque model limiting engine torque output until the revs move higher, but I don't know how to fix it because I am not an experienced tuner, especially with the torque-based systems.

  9. #9
    Tuning Addict 5FDP's Avatar
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    If the engine is stock do not change the peak torque TM table. That table must be in line with what is really happening. You can't say it's making 500 ft lbs of torque when it only makes 300ft lbs. Be careful with the other TM tables too, you can't just max them out or disable them all if you want this torque based computer to play nice.

    I wish I knew more about that specific throttle problem to help more.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  10. #10
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    I changed the peak torque table due to the suggestion in this thread, which is actually the only thing I've found that made any difference at all. Before making most of the changes suggested in the thread, my throttle was taking until over 5000 RPM to open all the way.

  11. #11
    Advanced Tuner ZeroBoostBuick's Avatar
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    5FDP is pointing you in the right direction.

    The Peak Torque table when it's overshot it tends to close the throttle.

    My brother has a Verano with the E39a and noticed the stock tune in the scans would open the throttle all the way starting around 3,200 rpm. Then I changed the peak torque and now it doesn't open all the way until passed 4,200 prm, sometimes even 4,700 prm.

    Car's driving great and he doesn't want me to fine tune it anymore because he's very happy with it right now.

  12. #12
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    Okay, I will try it.

    I live at about 4500 feet altitude where the air pressure is only around 85% of sea level. Do you think it would help to actually reduce that table a bit below stock to bring it more in line with actual torque output due to reduced air intake?

  13. #13
    Advanced Tuner ZeroBoostBuick's Avatar
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    I can't say because I haven't tried going less than stock.

    Everything at 4,267 rpm and lower I'd put back to stock... then do at least 3 or 4 runs to see if the throttle opens up all the way earlier than now.

  14. #14
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    I set the peak torque table back to stock and now throttle is not opening fully until 5200-5300 RPM. So it made it worse.

    Anybody have other suggestions?

  15. #15
    Advanced Tuner ZeroBoostBuick's Avatar
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    At least you know now... but it can take a couple full throttle pulls before it allows the throttle to open sooner.

  16. #16
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    Bump. Still can't figure this out. I know the answer is out there but I can't find it.

  17. #17
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    Ever find an update/solution here? Really the only reason I haven't swapped to the Delphi ECU yet.

  18. #18
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    This is actually by design. The ECM only opens the throttle body as far as it needs to in order to reach maximum intake manifold pressure.

  19. #19
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    Different year but here is a tune i did on a 2016 impala. You may try turning off stall tq mgnt and brake tq management as well, it helped this car quite a bit on a launch and in 1st and 2nd gear.
    Attached Files Attached Files

  20. #20
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    But wouldn't physics say that not opening it all the way would then almost certainly cause more pressure drop than if it was opened all the way, irrelevant of the engine rpm/flow through the TB? Meaning if there's a point of great VE, the engine could actually be ingesting higher than ambient pressure, so any closing of the TB would then drop that back to ambient pressure? Unless I'm missing something about other functionalities (actual EGR, cam timing caused EGR, etc.) I cannot envision a reason this not opening the TB to 100% would be beneficial. I'm here to learn though, so I'm quite accepting that I have this wrong in my head. Looking forward to further discussion. Thanks!