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Thread: Is there a reason to optimize true vs actual driver demand torque after mods?

  1. #21
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    Quote Originally Posted by TriPinTaZ View Post
    I adjusted your VT a little more. Give this one a try. As a general rule, I have found that if you increase Virtual Torque you must also increase Driver Demand in those areas. 30% increase should still be adequate for this revision but if you see throttle closing again go ahead and bump the 100% Pedal Position by +5% or so.

    Attachment 99704

    Usually if Driver Demand is too low, the ECU resorts to closing the throttle. But there have been some strange things the ECU does in certain situations when the Torque Model is off. To SUPER SIMPLIFY what Howard quoted above, if the Torque Model is off, the reverse lookup that the ECU does will show too large of an error to make sense of. As a response the ECU will resort to random shenanigans including closing the the throttle and random Torque Management Advance(timing pulls).
    So you are right, I took my current tune and flashed it with the VT increases you made and it made the throttle close:
    Capture.PNG

    I reflashed it again but put the increased driver demand tables that you had and it seems good now except it is still showing a very slight timing pull but not in every WOT run only on this one for some reason, however its not enough to worry about:
    Capture2.PNG

    Also I read the entire patent for one of the torque based controls, I couldn't really fully comprehend most of it but I did get out of it that it dose have 4 "modes" of operation and it does have a driver pedal filter and other things (which GM didn't seem to program to well since I can still take off from stoplights and the pedal feels so twitchy, especially with the car as stiff as it is).

    I was hoping to figure out more about what kind of behavior it will have if there is a sudden immediate torque reduction request (WOT upshift), most "tuners" really like to increase the minimum spark advance table. I think they use this as a half way attempt to reduce torque reduction on WOT upshifts. However one really good thing about this (it will break the tires loose since all the engine inertia plus engine torque is allowed to go to the tires at once) is it stops the extremely bad poppy, rattling, fart noise of the exhaust that sounds incredibly bad. When I try to increase the min timing table I get inconsistent behavior, sometimes it will cut throttle (since it can't accomplish the torque reduction through timing retard because of the limit) and sometimes it won't. I also have seen it cut fuel injectors off as well. It would be nice to understand how it does this so we can get rid of the awful fart can exhaust noise but still have proper torque reduced shifts?
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  2. #22
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    Quote Originally Posted by cmitchell17 View Post
    So you are right, I took my current tune and flashed it with the VT increases you made and it made the throttle close:
    Capture.PNG

    I reflashed it again but put the increased driver demand tables that you had and it seems good now except it is still showing a very slight timing pull but not in every WOT run only on this one for some reason, however its not enough to worry about:
    Capture2.PNG

    Also I read the entire patent for one of the torque based controls, I couldn't really fully comprehend most of it but I did get out of it that it dose have 4 "modes" of operation and it does have a driver pedal filter and other things (which GM didn't seem to program to well since I can still take off from stoplights and the pedal feels so twitchy, especially with the car as stiff as it is).

    I was hoping to figure out more about what kind of behavior it will have if there is a sudden immediate torque reduction request (WOT upshift), most "tuners" really like to increase the minimum spark advance table. I think they use this as a half way attempt to reduce torque reduction on WOT upshifts. However one really good thing about this (it will break the tires loose since all the engine inertia plus engine torque is allowed to go to the tires at once) is it stops the extremely bad poppy, rattling, fart noise of the exhaust that sounds incredibly bad. When I try to increase the min timing table I get inconsistent behavior, sometimes it will cut throttle (since it can't accomplish the torque reduction through timing retard because of the limit) and sometimes it won't. I also have seen it cut fuel injectors off as well. It would be nice to understand how it does this so we can get rid of the awful fart can exhaust noise but still have proper torque reduced shifts?

    You need to tune your TCM to reduce Torque Management on upshifts. It is definitely worth it if you haven't done so. The immediate torque reduction request is to allow the transmission to shift. You can tighten up these areas and reduce the amount of torque drop but you will need some to safeguard the transmission. Minimum Spark is essentially the "floor" that Torque Management Advance is allowed to reach. You can easily create poor drive-ability by altering this table incorrectly. It is no longer the proper place to adjust your timing drop on upshifts since the TCM's can now be tuned.
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  3. #23
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    Quote Originally Posted by TriPinTaZ View Post
    You need to tune your TCM to reduce Torque Management on upshifts. It is definitely worth it if you haven't done so. The immediate torque reduction request is to allow the transmission to shift. You can tighten up these areas and reduce the amount of torque drop but you will need some to safeguard the transmission. Minimum Spark is essentially the "floor" that Torque Management Advance is allowed to reach. You can easily create poor drive-ability by altering this table incorrectly. It is no longer the proper place to adjust your timing drop on upshifts since the TCM's can now be tuned.
    This is what I have changed currently on the TCM side:
    Capture.JPG

    The "limit torque management" seems to have some effect on some sort of ramp in and out before and after the shift, especially on downshifts. Which I actually like because the car seems way too overly violent on downshifts, but it does seem to give the placebo effect of increasing power when you turn these off. Either way I believe the TCM ignores most of these tables since when you change them to use "throttle" or "no throttle" it doesn't have any effect because throttle (predicted) torque control is never used its all timing (immediate) based. Unless that's not what they mean here by "throttle"?

    I have tried adding a progressive (as torque increases > decrease) adder modifier and negative 1 values for the shift adder which would subtract a percentage of shift torque on upshifts. This had no effect and I believe the TCM ignores these tables:
    Capture.JPG


    Do we have access to anything to properly tune torque reduction on upshifts? I know everyone accuses the torque reduction to be way over excessive, which it does seem to be that way, given the way GM is calibrating things now with spark maps and other stuff, I would still think the torque reduction is optimized pretty well for long term durability and minimized shift timing? Maybe instead of it reaching almost -5 or -10 degrees of timing at peak reduction, maybe it should be more like 0 or 5 degrees positive?
    Last edited by cmitchell17; 05-24-2020 at 12:34 PM.

  4. #24
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    Here is the Tune I have right now so far.
    Attached Files Attached Files

  5. #25
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    Quote Originally Posted by MartyB2017SS View Post
    Here is the Tune I have right now so far.
    Do you have a cam and valvetrain upgrades? What other mods do you have?

    Also do you have your log file?

    You can put your timing where ever you want to, but its more important to have proof that its better that way, without a OEM level engine lab with multi million dollar equipment and a load bearing engine dyno you are basically in the dark. I don't trust "tuner shops" and there dyno runs to be controlled enough in a way to prove more is better when it comes to timing. However, I do trust, and a lot will disagree on this, is the stock GM calibration, we have torque output as a function of timing defined in the virtual torque tables right in front of us. I personally trust this 100 times more than I would a "tuner" a lot of people wont agree though. Also keep in mind that the HP Tuners shows the virtual torque as a series of different tables based on their "interpreted" spark advance value, however, I believe this isn't actually the current value of spark advance but more the difference from MBT (mean best torque or mean best timing bascially the theoretical perfect timing value given the load and conditions). Either way it dosent' really change anything the concept is still there.

    For a quick reference you can look in the MBT table in the timing section and see the theoretical "best" timing. I would assume (and this is a very big and important assumption) that this is MBT timing for standard air conditions (around room temp, sea level, etc.). Note that there is also a alcohol modifier table. I will admit I am being hypocritical since I would never run 16 degrees of timing at WOT and think I'm making the best power (since at max airmass (.88) the MBT table is indicating around 25 degrees of timing minus 9 from the alcohol table gives you 16 degrees). All that being said the stock high octane spark table (as long as you don't have KR) I think its the optimal tune. Now things change if you have changed the combustion system or increased compression.