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Thread: Whats the torque/ inverse calculation?

  1. #1
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    Whats the torque/ inverse calculation?

    I've been getting asked this question by a lot of people. So I figured Id just make a post.

    Its popular and yes you can use angle error and modify the torque values then calculate the inverse of the load tables. I do not suggest it as calculating the inverse for the top inverse row the torque is 0 is impossible.
    Heres why:
    Its an inverse relationship which is y=1/x.
    x being air load and y being indicated torque.
    It can also be x=1/y. This is where dividing by that 0 is impossible.

    If you look at the inverse relationship Y will go to infinity before x is 0 and x will go to infinity before y goes to 0.
    If you look at the inverse relationship indicated torque will go to infinity before air load is 0 and air load will go to infinity before indicated torque goes to 0.
    ETC torque/desired torque/ driver demand torque can all go below 0. basically you need to use this as your 1 or the "constant" to establish your base air load and indicated torque.

    inverse.png

    The way I suggest to do it is start by modifying the load values. I first find my desired/ETC/driver demand torque in the torque tables. The PIDs read nearly the same when things are not way off.
    To find our values to replace that 1 and get our desired torque values we can multiple the load and torque of the Y axis of the torque and inverse tables. X*Y=1 As long as your maximum driver demand falls somewhere near the bottom of the tables everything should work out. And because ETC goes below 0 we end up with a load floor for that 0 torque row. All you have to do is setup a Graph with these values in the rows and using PID ETC TQ. Then set the columns to the RPM range in your tables. I suggest making them slightly higher than your red line. Then have the table fill with your air load. Drive around trying to hit every RPM and every load to fill in the table. Filter the graph by MPs so you can apply the load to the correct MP. After applying the new load values you will need to click smooth the entire table a few times to get it smoothed out. You can then take these new values and apply them in to the attached sheet to get the new torque values. The torque values in the top table do nothing(except the top row) in this sheet so it cant be used for the angle error method.

    shouldn't take to long for all IPC error to clear up and the car driving much better. .

    inverse.xlsx
    Last edited by murfie; 08-04-2017 at 02:50 AM.

  2. #2
    You really helped me out a lot with this, and it's great information. Having graphs to populate your torque tables and take the guess or dyno work out of it is really useful.

  3. #3
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    The ECM has 3 different torque values that I've noticed:Engine Brake Torque, Engine Indicated Torque Reference and ETC Torque Request. There are a couple more but the values are always the same as one of the 3 I listed first.

    If I understand what you are saying you are logging ETC Torque Request for various loads and rpm and then updating the Torque Tables with these new values. Then the inverse tables are updated from the new torque tables?

  4. #4
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    Quote Originally Posted by Plimmer View Post
    The ECM has 3 different torque values that I've noticed:Engine Brake Torque, Engine Indicated Torque Reference and ETC Torque Request. There are a couple more but the values are always the same as one of the 3 I listed first.

    If I understand what you are saying you are logging ETC Torque Request for various loads and rpm and then updating the Torque Tables with these new values. Then the inverse tables are updated from the new torque tables?

    Nope you misunderstood. I do not find the new torque values I base the inverse off ETC and load as they come from sensors. The torque values are a calculated number. The 0 torque row gives it away that the rows are not part of the inverse as infinity is inverse of 0.

    ETC torque request is the row PID of my graph. Multiplying the load rows and torque rows of the tables in the editor gives you the values to use in the rows of your graph. Yes eco boost have 2.4 load and you get a value of over 1000 which you never get close to for ETC torque. It still works out.

    The columns of the graphs would be RPMs. The values are directly from the tables in the editor. Rescaling is easy for higher revving motors.

    The parameter to populate is air load.

    These values get copied in to inverse tables. Smoothed. Then the final values are used in the sheet above to get the inverse calculated torque. The 0 torque row stays the same torque values. The new load values become the base load for zero or negative ETC request.

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    Awesome, thats clear, I'm going to give it a try. Car is twin turbo and GT350 TB and IM, so I'm seeing loads over 2.0 and rpm is up to 8,000 Everything needs to be rescaled, its running great now, but I'd like to refine it

  6. #6
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    Your tables under general and air charge section of the speed density tab should be as accurate as possible for best results.

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    Thank you for writing this up. Reading all your other post I learned this is what I needed to learn to get the torque tables set correctly.

    I'm still learning the scanner. Any chance I could get you to post screen shots of your graph setup? I do not yet know the syntax for filtering the MP tables and other stuff for correctly setting up graphs.

    A MAF transfer graph setup would be awesome too. You understand this stuff to a level I wish to achieve someday. I have a good understanding of what to do, now I have to learn how to do it.

  8. #8
    Advanced Tuner Auto-Hentzschel's Avatar
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    here is a good description, how the torque tables works and how to calculate them.

    http://www.masterenginetuner.com/201...e-maps-p1.html

  9. #9
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    I read that article when it came out. I did not gain any thing from it on how to tune these tables, other than I needed a dyno. They didn't explain a few things. How ETC relates to these tables, just that it does, being a major one. I know you can get your dyno numbers and correlate them to RPM and load in your log, but not everyone has a dyno or the money to rent one. Also partial throttle load/RPM values and torque values from a dyno would not be easy to correlate and thats where most people get their surging they can't fix.

    What you can get out of a log is load. This should be the variable used to base torque off not the other way around. When you know an inverse relationship is y=1/x and not x/y=y/x its easy to figure out you need to know how demanded torque relates to these tables to fix the load they call for.
    Last edited by murfie; 08-06-2017 at 06:33 PM.

  10. #10
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    murfie

    Pretty cool you can set this up to do the math for you. I got numbers not sure if they are right. I could not add Air Load to a graph chart or gauge. No matter what I did it just won't show numbers using Air Load. I used Absolute Load, which looks almost like Air Load numbers most of the time. Close enough to play with how it works anyways.

    Did I get close?
    Attached Files Attached Files

  11. #11
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    Not sure why you couldnt get air load to work. All I did was select it instead of absolute in your table.xml.

    They are not that much different. I think if you turned up or matched their polling speed they would be the same.

    Airload v Absolute.PNG

  12. #12
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    Whats the torque/ inverse calculation

    Murfie, see below instructions and let me know if this is the right way to do what you are suggesting with Torque Table Tuning. Assuming this works for Torque error, would this also help with throttle angle error as well? I am still battling the tuning of my GT350 TB on my GT and was planning on trying this method soon.



    Bill
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    Last edited by R8Bill; 08-09-2017 at 05:45 PM.

  13. #13
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    Do not paste new torque values into rows in editor. Leave what you had.

    They are only for the ETC TQ in the graph.

    Only values you are changing are in the tables.

    The only time you would need to modify row values are to resale for peak air load and peak ETC torque.

  14. #14
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    gotcha! I will try and let you know how she works

  15. #15
    His method works very well. My torque errors went from the 400s to 40s with just one log. I haven't been able to drive my car much due to working a lot, but the more I drive, the more I will smooth it all out.

    As with any histogram, the more data you can gather, the better it will be when you copy over. Just a few cells will cause it to be all over the place.

  16. #16
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    R8Bill - Nice job so far. Could you make the changes that murfie suggested (keeping row values the default values for the torque tables) in your tutorial? The final could be a sticky that would clear up this contentious issue for many. Thanks for the effort and thanks to murfie for the direction.
    2012 Mustang GT with S/C
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  17. #17
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    Quote Originally Posted by 15PSI View Post
    R8Bill - Nice job so far. Could you make the changes that murfie suggested (keeping row values the default values for the torque tables) in your tutorial? The final could be a sticky that would clear up this contentious issue for many. Thanks for the effort and thanks to murfie for the direction.
    Here I updated instructions....Need Murfie to confirm

    Murfie Torque Table Instructions-1.jpgMurfie Torque Table Instructions-2.jpgMurfie Torque Table Instructions-3.jpgMurfie Torque Table Instructions-4.jpg

  18. #18
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    Thx again for doing that.
    2012 Mustang GT with S/C
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  19. #19
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    Murf, I did the following and modified my torque tables per the attached spread sheet which is similar to yours, but my torque errors doubled. Here is a below and after histogram showing torque error increasing. Is there something wrong here? I followed the steps in the aforementioned instructions I posted.

    Murfie inverse-81017.xlsxTorque Error.jpgTorque Error-After.jpg

  20. #20
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    Why do you have 2.6 load or higher in some MPs in the lower left corner? Thats obviously wrong and will cause the entire table to be off after smoothing. When you get close or only entered a few cells of data smoothing just spots and not the entire table is needed.
    Last edited by murfie; 08-12-2017 at 12:50 AM.