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Thread: what parameters control Max Engine Torque values?

  1. #1
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    what parameters control Max Engine Torque values?

    Hi guys,

    Ive been trying to dial in my 2014 5.3l GMC Sierra with a Whipple 2.9 running 13.5psi of boost and as with every other supercharged 2014 truck ive come across power surges at part throttle cruising. Now I know whats causing it and its NOT simply modifying driver demand unless you want the truck to drive like crap with very bad throttle response. It seems the solution lies within being able to control the Max Engine Torque values WITHOUT effecting Delivered Engine Torque, meaning that simply bumping up the Torque Coefficients randomly isn't going to help.

    I tried increasing "Peak Torque" however it seems that this table does absolutely nothing on my truck, and doesn't even mess with PE, I tried 5000lb-ft with no luck, so does anyone have any idea WHAT tables increase or decrease the Max Engine Torque only?

    Since I spent SO much time on this, I could write some kind of tutorial on how to get rid of the throttle surges with forced induction for anyone who has problems with it granted I find what im looking for to begin with!

  2. #2
    Senior Tuner Higgs Boson's Avatar
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    Max Torque Timing also influences your torque calculation

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    I too would love to understand what "drives" the Max Torque PID. It seems that the "Peak Torque" PID is always higher than "Max Torque" and I've also noticed that sometimes the "Delivered Torque" is higher than "Max Torque" (but never higher than Peak Torque).

    Just don't understand how Max Torque and Peak Torque are related to each other and how to use these PIDs to make decisions about tuning. Also curious if there is any way to alter the Max Torque or not....

  4. #4
    Senior Tuner Higgs Boson's Avatar
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    Airmass A,B,C,D Tables
    Max Torque Timing Table
    these are known to alter Delivered Torque

    I've gotten to the point where I just get all the torque based tables as close to what the combination is really making and then just verify it isn't pulling spark or closing throttle and A/F is correct. After that, how could it be limiting power?

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    Where do you find the "Max Torque Timing" table? Don't believe I've seen that one anywhere before....

    Thanks.

    EDIT: DOH! I see it now - not sure how I missed that one before! It's under Engine->Spark->Advance, under the "General" heading in the right-hand column.
    Last edited by jtrosky; 06-23-2015 at 12:25 PM.

  6. #6
    Senior Tuner Ben Charles's Avatar
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    Higgs I've seen that on the max tq timing too. I usually set that table a little higher than my high octane and noticed I was getting timing from the max tq timing table.

    Max tq timing under the spark tab

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    Quote Originally Posted by Higgs Boson View Post
    Airmass A,B,C,D Tables
    Max Torque Timing Table
    these are known to alter Delivered Torque

    I've gotten to the point where I just get all the torque based tables as close to what the combination is really making and then just verify it isn't pulling spark or closing throttle and A/F is correct. After that, how could it be limiting power?
    Well what you're doing sounds right for WOT tuning and to make sure it isn't limiting, however on a Forced Induction application, part throttle drivability suffers and will cause throttle surges unless you lower Driver Demand significantly, after which you have almost no throttle response left and would require 30% pedal just to keep the car at a steady speed etc...

    Whats happening is the following:

    youre driving in 3rd gear at 2500rpms and requesting (Driver demand) 40KW of power. At this RPM that equates to 150nm of torque, however Max Engine Torque is at 250nm, everything is fine. Now as soon as the car shifts into 4th gear and revs drop to 1250rpms (while you are maintaining the same pedal position) meaning you are still requesting 40KW but at 1250rpms that equates to 305nm while Max Engine Torque is at 200nm. The fact that you are requesting MORE than what the ECU thinks the max engine torque is causes it to swing the throttlebody open to "meet" the requested torque only to be hit with a big surge in power, overshooting the requested torque and then brought down via the intergral and proportional torque controls to where they should be.

    The same thing happens anytime a sudden change in throttle position causes a large sudden rise in driver demand torque, approaching or exceeding Max Engine Torque.

    The only way around this problem is to lower driver demand so it doesn't approach or overshoot the Max Engine Torque values which sucks, or find a way to INCREASE Max Engine Torque WITHOUT consequently increasing delivered torque.

    In this case if my supercharged truck gives me a Max Engine Torque value of 300nm at 2000rpms and a high TPS, then I want to be able to change it to say 700nm without altering anything else.

    Editing the Airmass torque tables unfortunately increases Max Engine Torque but also increases delivered torque (hence the reason why shifts become firmer).
    Last edited by ayousef; 06-23-2015 at 01:04 PM.

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    Quote Originally Posted by jtrosky View Post
    I too would love to understand what "drives" the Max Torque PID. It seems that the "Peak Torque" PID is always higher than "Max Torque" and I've also noticed that sometimes the "Delivered Torque" is higher than "Max Torque" (but never higher than Peak Torque).

    Just don't understand how Max Torque and Peak Torque are related to each other and how to use these PIDs to make decisions about tuning. Also curious if there is any way to alter the Max Torque or not....
    I cant understand the recurrent use of words with similar meanings like peak or max however I also think that there are more tables in the ECU that HPTuners are still not giving us access to for one reason or the other. Changing the Max Engine Torque values is essential in tuning any FI application on vehicles that have a VSS vs Pedal position Driver Demand table. I know that the C7 Z06 tables use RPM vs Pedal position which helps a lot.

  9. #9
    Senior Tuner Higgs Boson's Avatar
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    Quote Originally Posted by ayousef View Post
    Well what you're doing sounds right for WOT tuning and to make sure it isn't limiting, however on a Forced Induction application, part throttle drivability suffers and will cause throttle surges unless you lower Driver Demand significantly, after which you have almost no throttle response left and would require 30% pedal just to keep the car at a steady speed etc...

    Whats happening is the following:

    youre driving in 3rd gear at 2500rpms and requesting (Driver demand) 40KW of power. At this RPM that equates to 150nm of torque, however Max Engine Torque is at 250nm, everything is fine. Now as soon as the car shifts into 4th gear and revs drop to 1250rpms (while you are maintaining the same pedal position) meaning you are still requesting 40KW but at 1250rpms that equates to 305nm while Max Engine Torque is at 200nm. The fact that you are requesting MORE than what the ECU thinks the max engine torque is causes it to swing the throttlebody open to "meet" the requested torque only to be hit with a big surge in power, overshooting the requested torque and then brought down via the intergral and proportional torque controls to where they should be.

    The same thing happens anytime a sudden change in throttle position causes a large sudden rise in driver demand torque, approaching or exceeding Max Engine Torque.

    The only way around this problem is to lower driver demand so it doesn't approach or overshoot the Max Engine Torque values which sucks, or find a way to INCREASE Max Engine Torque WITHOUT consequently increasing delivered torque.

    In this case if my supercharged truck gives me a Max Engine Torque value of 300nm at 2000rpms and a high TPS, then I want to be able to change it to say 700nm without altering anything else.

    Editing the Airmass torque tables unfortunately increases Max Engine Torque but also increases delivered torque (hence the reason why shifts become firmer).
    MAF only or properly tuned VE?

  10. #10
    Senior Tuner Higgs Boson's Avatar
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    Quote Originally Posted by ayousef View Post
    I cant understand the recurrent use of words with similar meanings like peak or max however I also think that there are more tables in the ECU that HPTuners are still not giving us access to for one reason or the other. Changing the Max Engine Torque values is essential in tuning any FI application on vehicles that have a VSS vs Pedal position Driver Demand table. I know that the C7 Z06 tables use RPM vs Pedal position which helps a lot.
    you can change any of them to pedal vs rpm if you are so inclined. just enable it right above the DD tables.

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    I'm just curious, did your tune originate from whipple? Only reason I ask is because I've got one I've got to tune, that I already fixed some trans issues on and it's had this surge durring cruise since day 1 with the whipple tune. With what little I know about these new platforms, I can tell whipple didn't tune it anywhere near correctly with only modifying "A" mapped driver demand tables and not doing all the rest equally? Fueling was also way off and sd was untouched...

    Anyway, was just wondering. Hopefully hp can get the datalogger fixed very soon so I can start working on this thing
    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

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    whats wrong with the data logger? works fine with me lol. Anyways the surge thing has nothing to do with Whipple, with that said a canned tune is what it is. I don't use the Whipple tune though, infact my truck is making 14psi I verified tonight, and is running on 93 octane gas and no meth so I guess Im waiting for the motor to blow up?

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    Quote Originally Posted by Higgs Boson View Post
    MAF only or properly tuned VE?
    MAF only

    Quote Originally Posted by Higgs Boson View Post
    you can change any of them to pedal vs rpm if you are so inclined. just enable it right above the DD tables.
    So you enable that then edit the VSS axis into RPM values? I doubt that's how it works but what do I know?

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    Senior Tuner Ben Charles's Avatar
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    Post the tune and I'll take a look

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    Senior Tuner Higgs Boson's Avatar
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    Quote Originally Posted by ayousef View Post
    MAF only



    So you enable that then edit the VSS axis into RPM values? I doubt that's how it works but what do I know?
    seems like you might want to tune the VE for reference purposes....?

    yes, enable NV, change the axis, then you also have to change the values in the table of course..... maybe start with the Z06 data?

  16. #16
    Nobody tunes VE tables on these things Higgs. Not that this guy hasn't but I bet I tune 1 vehicle a month that comes from a "tuner" with a mild cam and stock VE tables. They put out good numbers on the Dyno but surge and labor down the highway.
    2.25 looks like it has a nice feature that will make it a lot less cumbersome too👍

  17. #17
    Senior Tuner Higgs Boson's Avatar
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    Quote Originally Posted by mm_n_p View Post
    Nobody tunes VE tables on these things Higgs. Not that this guy hasn't but I bet I tune 1 vehicle a month that comes from a "tuner" with a mild cam and stock VE tables. They put out good numbers on the Dyno but surge and labor down the highway.
    2.25 looks like it has a nice feature that will make it a lot less cumbersome too��
    exactly.

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    How do you tune VE for these new vehicles?
    what tables do you change and what PID's do you use?

  19. #19
    Senior Tuner Higgs Boson's Avatar
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    in your Editor go to the Edit Menu and choose VE Table Configurator or Editor of whatever it says and it will display your VE table based on your VVE tables. You can scan for error in a histogram and apply it, then export coefficients.

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    I haven't tuned VE and don't understand why I have to, its disabled anyways and the only time I would need it is if my MAF sensor fails.

    The issue at hand however is completely different, what happens is if predicted torque goes HIGHER than Max Engine Torque, the ETC surges. The only way around this is to lower driver demand (a lot), or to limit predicted torque by reducing Peak Torque table (which also makes part throttle drivability suck), OR the real solution would be to find out how to increase the "max engine torque" values only WITHOUT increasing delivered torque. Changing the torque coefficients seem to increase/decrease both max engine torque and delivered torque.