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Thread: What exactely is Force motor current?

  1. #1
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    What exactely is Force motor current?

    Is there any benefit to changing the Force motor current in the trans tables?
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  2. #2
    Advanced Tuner n0dih's Avatar
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    Lower FM current is higher trans line pressure (main line)

    Quote Originally Posted by Turbo Tim
    Is there any benefit to changing the Force motor current in the trans tables?

  3. #3
    Potential Tuner slowhand's Avatar
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    Quote Originally Posted by n0dih View Post
    Lower FM current is higher trans line pressure (main line)
    Then why do tuners change the 100% col.to (1245) if lower FM is more line pressure??

  4. #4
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    Tuners don't do that, GM does it and it's retarded. It presumes
    you aren't ever going to go over the "max line %" factory number
    in the tune file. If you did then you'd start to blow off line pressure
    when you need it most. Set the 100% column to 0 or the same
    as the 96% column.

  5. #5
    Advanced Tuner Programmer's Avatar
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    Bill -- this is something that really should be fixed in HPT.

    That's an error with the table interpretation...100 isn't '1245'...although HPT shows that it is. It's not a GM error at all.

    If it was a real value, you'd pretty much have an instant trans failure.

    The transmission PCS positive and negative table is 17X17, not 18x17.
    Last edited by Programmer; 12-14-2008 at 11:55 PM.

  6. #6
    the table is actually 18x17 in the code, GM limits the lookup so that the 100 column is never looked up (96 is the max). You can change the 100 column to anything and it will never be used.
    I count sheep in hex...

  7. #7
    Advanced Tuner Programmer's Avatar
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    I'm just making a suggestion. Those FM tables have always been 0-96 (conversion of pressure to force motor current).
    Yes, in hex--the table appears as 18x17 ... but the code shows 17x17.
    EOL fix.

  8. #8
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    Interesting, or at least odd, thing about this extra column.. It is the max value on certain years of Grand Prixs, and all 0 in others.

    I have changed it from one extreme to the other and have yet to see an effect. However, if you change the Maximum Line Pressure from 96 to something higher, this should have an effect right? Or are these bins really hard coded somewhere to limit it to 96 even if you change the value higher?
    97 Grand Prix GTP (not going to bother listing mods in detail) 1 messed up 97 PCM with about 30-50% of a 2003 calibration and parts of a few others.

  9. #9
    the pressure is limited to 96 (hardcoded)
    I count sheep in hex...

  10. #10
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    hmm. the value in the editor doesnt have much use then does it.. (the max line pressure settins that is 96 on every v6 bin I have looked at). Not that the 1 extra column is would add that much resolution anyway.
    97 Grand Prix GTP (not going to bother listing mods in detail) 1 messed up 97 PCM with about 30-50% of a 2003 calibration and parts of a few others.

  11. #11
    Advanced Tuner n0dih's Avatar
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    I don't think I have seen any that haven't been higher except 4L80E's. Not sure if it is right, but my 99 K2500 allows me to go to 1024 in the base shift pressure table. But normally this is max of 96... Have to see if that needs fixing....