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Thread: Throttle closing on gear changes

  1. #1
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    Throttle closing on gear changes

    went to the track this weekend, tack prep was not that good, but noticed that that the car seems to be closing throttle, shutting the injectors and pulling timing in all the shifts, making the car sound like a manual car, but checking videos on faster bolt on cars i noticed that they all sound like automatics, with no pause in gear changes making me think there is still some improvement to be made.

    the car has a intake, airforce intake manifold, 2'' long tube headers, no cat and some borla npp exhaust, a circle D 3500rpm stall converter, i was racing on VP X85 fuel, it puts down 469whp and its gone 119 mph pretty consistently on full weight trim (except drag pack)

    This pass the car had a 1.8x 60ft, with pretty bad traction on 1st gear so that could explain why so big of a dip in the throttle there, 2nd gear onwards it had good traction but still pulled some throttle.
    2dapuntuable 3.hpl

    This is the tune, i changed the shift points to a higher rpm to take advantage of the intake manifold and tried some of the stuff i normally did on the 6l80 which i know its a totally different animal
    cachalote setup2.hpt

    Could this throttle closing be blamed on my transmission tuning or is some tuning lacking on my engine and torque side of things?

  2. #2
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    All of those record passes you see are cars with tqm turned off.

    That being said, if you work on the torque model and trans tune it's very much possible to make the car pull timing and fuel only and leave the throttle open. You aren't logging enough pids to get any sort of decent assessment of the torque model, but if engine torque is going over max torque (and trans tq management is allowed to have free reign) you'll get shifts like you have currently.

  3. #3
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    You can also try disabling the control method under fuel/cutoff/dfco. Ive had that cause some issues with closing the throttle during shifts but what Sevinn said applies as well. These new gen ecms being torque based require more finesse

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    Quote Originally Posted by sevinn View Post
    All of those record passes you see are cars with tqm turned off.

    That being said, if you work on the torque model and trans tune it's very much possible to make the car pull timing and fuel only and leave the throttle open. You aren't logging enough pids to get any sort of decent assessment of the torque model, but if engine torque is going over max torque (and trans tq management is allowed to have free reign) you'll get shifts like you have currently.
    well i didnt log any toque stuff on the track, ill keep that in mind next time i go, but i did log them at the dyno, dont know if its any use in this situation.
    dynoc856.hpl

  5. #5
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    Judging by that log alone I don't think it's closing due to limiting, that being said early in the pull engine torque did end up over max torque.

    I think your trans tune could be worked on a little to get the shifts working a little closer to what you are expecting. Your reported torque also decreases dramatically as the run goes.

  6. #6
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    I noticed you didn't disable the "high volt test" in engine diag section. The pcm will pull power if it sees too much of a drop in map. Worth a try.

  7. #7
    Senior Tuner eficalibrator's Avatar
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    ...or you could calibrate your airflow and torque models correctly and let the system work as designed. If you do that, it only pulls the torque necessary to avoid destroying the clutches on the shift and no more.

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    Quote Originally Posted by eficalibrator View Post
    ...or you could calibrate your airflow and torque models correctly and let the system work as designed. If you do that, it only pulls the torque necessary to avoid destroying the clutches on the shift and no more.
    Is there anything in particular that jumps at you from the logs?

    I do want the system to work as designed

  9. #9
    I don't have any Get V experience at this point. Lots of Gen IV. Gen IV transmission torque management only uses ignition timing, right? Am I understand this thread correctly, that Gen V is using throttle, fuel and ignition to limit torque during shifts?

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    Quote Originally Posted by griffincox View Post
    I don't have any Get V experience at this point. Lots of Gen IV. Gen IV transmission torque management only uses ignition timing, right? Am I understand this thread correctly, that Gen V is using throttle, fuel and ignition to limit torque during shifts?
    Yes because of the way the torque based controller handles torque requests, and how quick or how dramatic of a change in delivered torque needs to be made. It will use a combination of the three.

  11. #11
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    This is all in your torque tables. Really simple actually.

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    I guess I should explain the high volt test disable. The MAF cannot compensate for the sudden drop in pressure from a performance based tune. At least that's what the Tuning School books say. I never tried tuning a gm without this step. I drive a 2017 silverado as my daily so yes, I cut my teeth on Gen V.

  13. #13
    Quote Originally Posted by Mbrowning View Post
    I guess I should explain the high volt test disable. The MAF cannot compensate for the sudden drop in pressure from a performance based tune. At least that's what the Tuning School books say. I never tried tuning a gm without this step. I drive a 2017 silverado as my daily so yes, I cut my teeth on Gen V.
    Any more details? This seems like a high voltage (high pressure) diagnostic. If I have a LS9 (3 Bar) map on an L86 running 7-8 psi boost I image this is irrelevant? It won’t get anywhere close to the top of the range

  14. #14
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    try this

    load this up and give it a shot see if helps it shift quicker and with out so many limits going on. And I didnt touch the trans tables at all. This was all engine stuff.
    Attached Files Attached Files
    First 9 second 6th gen lt4 zl1 stock blower SHC SBE boost only.

    2013 cadillac ats 2.0t Big turbo-gone
    2007 tahoe 5.3 lsa blower on 14 lbs boost 6l80e swap 2009 os
    2017 zl1 a10 big gulp/2 inch headers/ 9.55 lower/ e85/bigger hx /103mm tb / Synergy trunk tank and underhood kit/methanol injection with torqbyte controller and prometh pump / Jokerz performance R&D ported stock blower/ lme cnc heads /GP tuning custom cam. So far 9.30@150