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Thread: Is this Limiting?

  1. #1
    Senior Tuner Higgs Boson's Avatar
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    Is this Limiting?

    According to:
    https://www.hptuners.com/help/vcm_ed...vanced_e78.htm

    "For the throttle to remain 100% open and the turbo wastegate to be fully closed, the driver demand (predicted) torque request must always exceed the calulated engine torque."

    AND

    "Maximum Engine Torque: The maximum possible engine torque, this should be higher than Predicted Engine Torque Cmd otherwise it is limiting."

    So, Predicted Torque must exceed Calculated Torque otherwise the throttle won't be 100% open.
    However, Maximum Engine Torque must exceed Predicted Torque, which mine does not.

    Am I being limited and if so, how and where??? Please see attachment.

    TqPic.jpg

  2. #2
    Advanced Tuner Road's Avatar
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    Etc is not limiting. I saw your other post about no power increase remember pe enrichment is not linear with throttle position its torque bias so you may need to adjust or make sure it's coming on when you want. I am curious have you made any improvements to fuel economy?

  3. #3
    Senior Tuner Higgs Boson's Avatar
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    I do get a power increase when pe conditions are met. I also disable the torque based enable table for PE. My PE is only activated on Pedal position.

    My other post is about ETC Position jumping to 100% when pedal is still at 50 or 60 but the blade is not actually at 100% (I can tell because the truck does not change it's power delivery (even if it stayed at stoich it would at least increase acceleration a little).

    I agree that in the pic above ETC is not limiting. I am also getting my commanded spark. So my question is, What is limiting? If I am basing it on the E78 instructional guide, something is being limited..... ;-)

    Or is the guide misprinted? <--- I think that is my real question.

    edit: with regard to fuel economy, you can make a little progress with trans shift points. imo, that's the biggest improvement. command shifts at 2000 rpm for TPS up to like 40% and you can really roll into the throttle to get up to your cruise speed more quickly but also keep RPMs low while doing it.
    Last edited by Higgs Boson; 04-08-2015 at 07:12 AM.

  4. #4
    Advanced Tuner Road's Avatar
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    I was thinking maybe spark but it's hard to help without the tune. I have noticed the same on V8 Camaros

  5. #5
    Senior Tuner Higgs Boson's Avatar
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    I made a log for spark on the way to work today but I can't post it until this evening. I don't see any spark limiting at all except for during shifts, which is because I left it in......

    To me, it seems like the guide is either not clear or is misprinted.

    Hopefully Keith or Chris or Bill or someone will weigh in!

  6. #6
    Senior Tuner Higgs Boson's Avatar
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    Any info on this from anyone?

    Another example:

    Predicted Engine Torque Command - 480 ft lbs
    Engine Torque - 360 ft lbs
    Maximum Engine Torque - 350 ft lbs

    Is this limiting?

  7. #7
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    Have you tried increasing your maximum engine torque to 5% above predicted torque to see if it makes a difference? I would imagine that a torque request exceeding your maximum engine torque would produce a DTC.

    Since I'm ASSuming that "Torque" is just a table that references desired output in lb/ft, it is possible the PCM is generating output based not on driver demand, but another torque table?

  8. #8
    Senior Tuner Higgs Boson's Avatar
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    There is a Peak Torque Table and a Driver Demand table.

    None of the above three numbers are directly (yes indirectly) correlated to the PT or DD tables.

    My throttle is not closing and no spark is being pulled by TQ Mngmt.

    As my OP states, based on the link in the OP, Maximum Engine Torque needs to be higher than Predicted Cmd or it is limiting. But is it??? How? Not by spark, fuel, or air.....So how?

    Or is the guide wrong or am I misreading it?

  9. #9
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    Really reaching into the dark here... let's say there's nothing wrong with anything. If the vehicle is on an eddy current dyno, is the dyno set to not allow the vehicle past a certain RPM/MPH? I noticed that the vehicle's speed and RPM are very consistent unlike what I'd imagine if you were bouncing off a limiter.

  10. #10
    Senior Tuner Higgs Boson's Avatar
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    It's a street pull in the OP. 4th gear is 1:1. I believe the straight line is an illusion based on a wide range in the chart coupled with a 7 minute log.
    Last edited by Higgs Boson; 05-12-2015 at 04:25 PM.

  11. #11
    Senior Tuner Ben Charles's Avatar
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    Higgs I have noticed what you have seen on the throttle opening to 100% and actually not be at 100% yet. Still playing with WHY.

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  12. #12
    Senior Tuner Higgs Boson's Avatar
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    Yes, that is ETC Position....opens prematurely.

    I think we need a better list of what to log vs what. It's not as simple as just logging one PID per variable anymore. You have to log the four PIDs that control each variable.

    Progress is wonderful.

  13. #13
    Senior Tuner Higgs Boson's Avatar
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    bump......

  14. #14
    Advanced Tuner Road's Avatar
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    I have found torque limiting is not the only thing that controls throttle opening. Under high load conditions/high map conditions 100% throttle is not needed for the commanded AFR. If torque is not limiting you and your afr is where it is supposed to be then you should be good go. Test a pig rich pe and see if that helps keep the throttle open longer but it seems to me the closer map gets to 100 kpa the more it closes throttle.

  15. #15
    Senior Tuner Higgs Boson's Avatar
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    my throttle is not closing and no spark timing is being pulled. i am only asking from the standpoint of the help file/page statements listed above.

  16. #16
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    I saw the other thread on the pedal vs ETC. All this time I've been messing with driver demand thinking that is what my issues were. '15 2500hd, heads, cam, 2.9whipple, circle D stall. I thought with the upgrades on mine something in the tune was causing this issue. But anything over about 52-55% throttle pedal position, and ETC position jumps to 97%.

    To the current topic, I notice the same things as you mention in the first post, though I can never get ETC Position to go past 97% at WOT. I'd actually just sent you a PM requesting a stock file if you had one Higgs, as I do not have mine. Now that I have HP Tuners I'm curious to compare mine to a stock file and try to see if I can get to 100% ETC position. Hopefully see just what is limiting.

  17. #17
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    Setup a config to log roughly the same things. In hindsight reviewing them, wish I'd have logged ETC Area % to see where it was instead of desired.

    Attached is 2 logs and the config I used. First log is getting onto the interstate (~2:30) and another 70ish WOT hit (~4:08). Second log is cruising on interstate, some downshifts and rolling just enough into boost seeing what pedal % was doing.

    Though I did just go back to stock DD tables and strictly raised the 100% column.

    JasonW-Config-Pedal-And-TqManagement.cfg
    log_5-31-2015.hpl
    log2_5-31-2015.hpl

  18. #18
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    Did we ever figure out the hard rules as to what has to be higher than what has to be higher than what here?
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  20. #20
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    Good question! I’m glad I happened to come across this thread as I have been beating my head against the wall with the “max engine torque” PID reading low/lower than actual delivered engine torque on my Cruze. Which it appears it is limiting me as far as boost is concerned........possibly.


    The car runs strong, much stronger than a little 1.4 tiny turbo motor should but this whole thing with this max engine torque reading is driving me a little crazy. More than anything just wanting to know and understand every square inch of these operating systems these days. I know asking an awful lot! Lol.
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