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Thread: Any idea what the torque demand numbers mean?

  1. #1

    Any idea what the torque demand numbers mean?

    I'll give you the short version: I have been experimenting with the driver demand torque tables and the numbers are confusing. HPT says they are axle or engine torque depending on the application but on a stock Buick GS, the highest number is 215 and that is much lower than engine or axle torque. The bottom numbers are -11, how can it be negative torque? As an experiment I set the whole table to 10 and the throttle was totally dead but the idle would go up with speed and wouldn't come back down until the car stopped moving. Any ideas what the numbers mean?

  2. #2
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    That table basically tells the engine how much power you are requesting and throttle control ... setting it to high in the lower pedal regions will make the throttle uncontrollable and setting it too low will kill the power because its limiting the ecm ... you mostly just want to raise the settings in the upper end like from 70% and up ... maybe increase the mid section a little to help with part throttle but again dont get carried away

  3. #3
    Yes, I understand what the table basically does but If I am going to create a perfect table for my use, I need specifics. I need to know what exactly the numbers mean and what they relate to. Here is a map I use in dry conditions

  4. #4
    Senior Tuner cobaltssoverbooster's Avatar
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    before you open the table hover over its access button with your mouse. bellow a description will appear for that table. HPTuners always puts the table limits in there and units. If the units are not there (like ve table units dont exist for lsj or gen3 ls ecu's) then the values are deemed to be unit-less placeholders.

    it may be one of those things your going to have to accept as having unknown dimensions or unknown reference sensors. Welcome to coefficient based tuning...it pisses a lot of people off because of shit like this.
    2000 Ford Mustang - Top Sportsman

  5. #5
    Though they're for LNF's, it's worth reading these previous threads on optimum spark tables to get am understanding of how torque based ecu's use what I call "urgency tables".

    They are higher in terms of their ability to supercede other tables. Their absolute values are not as important as are their relative values.

    It's also very important to note that setting a value in a cell to its maximum possible value in a torque based ecu will cause a non-linear response. In other words, if the available scale is from -100 to +1000000, once you exceed the ecu's understood linear responses to achieve your request it reacts with an exponential response since it can't achieve the relative scale change rapidly enough. This results in runaway WOT situations.

    I have tested this extensively with many tables with the understanding of what could occur and what to do if it did occur. If you don't have another reference table which supercedes the one you are modifying in authority for final output and you set that table to maximum value you can end up in a runaway engine scenario.

    https://forum.hptuners.com/showthrea...-tables-how-to

    https://forum.hptuners.com/showthrea...K-Really-Works

  6. #6
    Quote Originally Posted by cobaltssoverbooster View Post
    before you open the table hover over its access button with your mouse. bellow a description will appear for that table. HPTuners always puts the table limits in there and units. If the units are not there (like ve table units dont exist for lsj or gen3 ls ecu's) then the values are deemed to be unit-less placeholders.

    it may be one of those things your going to have to accept as having unknown dimensions or unknown reference sensors. Welcome to coefficient based tuning...it pisses a lot of people off because of shit like this.
    Yes, I addressed this in my first post. HPTuners says it is engine or axle torque depending on application but it is clearly not either of these things. It looks like I'll just have to experiment to figure this out.

  7. #7
    Senior Tuner cobaltssoverbooster's Avatar
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    it could be calculated torque. values higher produce no resistance to output. lower values that are within the range of the actual calculated torque could produce a restrictive output result. therefore anything set super high would produce a full power output without interference.
    it acts as a torque demand request which makes perfect sense.

    i only made my general comment about no units because i didnt have access to a file i could open and verify what they put as units. remember the values will seem high because its a calculation not a direct measurement of torque.
    2000 Ford Mustang - Top Sportsman

  8. #8
    I think this table is overlooked a little, at least in terms of vehicle performance. I have tried dozens of different settings for this table and you are correct that too high of numbers down low produces an almost uncontrollable car. That first table I posted is what I used in the torrential downpour at the SCCA Solo Nationals last week and it made for a very easy to drive car. The second table is what I ran when it dried out the next day and it had the punch I needed. My wife in the rain and me in the dry


  9. #9
    Senior Tuner cobaltssoverbooster's Avatar
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    nice car!
    2000 Ford Mustang - Top Sportsman

  10. #10
    Quote Originally Posted by cobaltssoverbooster View Post
    nice car!
    Thanks. I finished 3rd and my wife was 6th

  11. #11
    It was fun to watch. Couldn't quite make up for the rainy day 1 that mixed up a lot of classes.

  12. #12
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    I was told that in the driver demand table on the LTG e39A ecm it is in kW of power Makes sense. In the 2016 newer LTG it is in axle TQ

  13. #13
    Quote Originally Posted by raflyer View Post
    I was told that in the driver demand table on the LTG e39A ecm it is in kW of power Makes sense. In the 2016 newer LTG it is in axle TQ
    I think I finally have an answer-Thank You!! Although, come to think of it, Kw is another way of measuring horsepower, not torque. Now, why are some numbers negative?
    Last edited by marksawatsky; 09-18-2018 at 02:00 PM.

  14. #14
    Ok, maybe this is a stretch but hear me out. The top number on the torque table for the 2012 Buick Regal GS is 215. If this is torque in kg/m it works out to 1555 ft/lbs. If the 215 is supposed to be torque at the axle, and you take the torque multiplication of a Regal GS in 1st gear, suddenly that 1555 ft/lbs seems entirely reasonable and the math works.

  15. #15
    Senior Tuner cobaltssoverbooster's Avatar
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    torque in the metric system is N*m so it would be Kg*m^2/s^2 and in imperial it is lbf*ft
    Torque (τ, Tau)= radius(m or ft) x Force (Newtons, Pounds Force)

    if this table was N*m then 215 would equate to 156 lbf*ft
    the conversion factor is .738 lbf*ft = 1 N*m

    depending on the dyno graph output of a stock file which im assuming makes closer to 215 at the axles, i would assume the table is axle torque in lbf*ft
    Last edited by cobaltssoverbooster; 09-19-2018 at 01:50 AM.
    2000 Ford Mustang - Top Sportsman

  16. #16
    Negative TQ is motored. Every time the wheels are spinning the engine the TQ is negative. You want to allow this to happen. For example, if you have zero tq at max engine speed and zero throttle it means the engine is still running in order to generate a net zero tq. You would basically be asking the engine to idle at 7000rpm.

    Daniel
    Last edited by TurboWood; 09-21-2018 at 11:38 AM.

  17. #17
    Can you explain this further? Does having negative numbers result in more engine braking when off the throttle? My throttle, even at idle is never lower than 22%, if I made all the cells below 22% negative numbers, would it try to drop the rpms every time I took my foot off the gas pedal?

  18. #18
    Senior Tuner cobaltssoverbooster's Avatar
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    trq engine - trq wheels = value table.

    table value will only be negative when the deceleration value is less than the wheel torque.
    if you have a hang issue then it could be commanding air to do what you experience now. its free to change, go test it if you can.
    2000 Ford Mustang - Top Sportsman

  19. #19
    Quote Originally Posted by cobaltssoverbooster View Post
    trq engine - trq wheels = value table.

    table value will only be negative when the deceleration value is less than the wheel torque.
    if you have a hang issue then it could be commanding air to do what you experience now. its free to change, go test it if you can.
    Are you sure about this? I'm still new to this, but engine vs. wheel tq will be gear dependent. If we ignore the trans/rear-end multiplication of TQ then really all we are talking about is the efficiency of these which doesn't seam important to me. In such a case I don't see how you would arrive at negative TQ. It seems more likely to me that these values are just engine.

    If I'm right, then a more negative value will result in more engine braking. Negative TQ should just be the FMEP and PMEP of the engine (again, if my understanding is correct). The only parameter we can impact is PMEP by closing the throttle. The zero-fueling TQ will become more negative as engine speed increases due to FMEP. It would be interesting to know if anyone has figured out what this is because I would think you would basically want that to occur at a fixed pedal position. Typically I would think this would be calibrated to be near zero pedal, but it might be interesting to have it occur at part throttle at higher engine speeds so that engine braking could be modulated.

    Daniel

  20. #20
    Engine braking is pretty important in a race car and next time I get a chance, I will be testing negative values to see if I get more engine braking