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Thread: How the Formula in the EIO section Works

  1. #1
    Senior Tuner S2H's Avatar
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    How the Formula in the EIO section Works

    the Formula in the EIO(AUX) section is called a transfer function
    it works by you teling it a step value and then telling it an offset from 0

    things you eed to know to figure out the formula for you device you are trying to use in the EIO section

    A) Voltage Maximum of the Device being used
    B) Value Represented by the (Volts=0) of the Device being used
    If the device doen not output 0 Volts then you need to used math to figure out what value 0 volts would equal.
    C) Value Represented by the Voltage Maximum of the Device being used



    then its (A)/(C-B) +B



    Example #1
    Wideband O2 Sensor (LC1)
    0 Volts= 7.35 AFR
    5 Volts= 22.39 AFR

    Volts Max = 5
    AFR represented by 0 Volts = 7.35
    AFR Max = 22.39

    so 5/(22.39-7.35) +7.35
    or in our EIO Formula
    Volts/ 0.3324 + 7.35




    Example #2
    Autometer P255 Fuel Pressure
    0.5 Volts= 0 PSI
    4.5 Volts= 100 PSI

    to get back to 0 since we do not know it yet

    (4.5-0.5) / (100-0) = 0.04
    0.5/0.04 = 12.5

    0 volts = -12.5 PSI
    4.5 Volts = 100 PSI

    Volts Max = 4.5
    Fuel Pressure Represented by 0 volts = -12.5 PSI
    Fuel Pressure Max = 100 PSI

    (4.5)/(100-(-12.5)) = 0.04

    Volts/ 0.04 + (-12.5)
    Last edited by S2H; 04-22-2007 at 11:20 AM.
    -Scott -

  2. #2
    Advanced Tuner MikeGyver's Avatar
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    With my new NGK/NTK wide band, .5V=9.00 afr, 4.5V=20.00 afr

    When I use my data, I come up with (4.5-.5)/20-9=.045
    .5/.045=11.11
    0v=11.11
    4.5v=20
    4.5/(20-11.11)=..506
    volts/.506+11.11


    What am I doing wrong?
    2000 GMC 2500 2-bar SD
    Stock LM7, LTs, TBSS intake manifold

  3. #3
    Senior Tuner LSxpwrdZ's Avatar
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    Instead of the transfer function just use the list instead. It's a simple define 0.00v, xx.xx afr and 5.00v, xx.xx afr. Cuts the figuring out the equation out of it.
    James Short - [email protected]
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  4. #4
    Advanced Tuner MikeGyver's Avatar
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    Thanks, but they did not provide a list, only a graph and the .5V and 4.5V AFRs. My problem stems from trying to figure the 0V AFR. It is obviously not 11.11 if .5V is 9.0 AFR
    Last edited by MikeGyver; 06-13-2014 at 06:56 PM.
    2000 GMC 2500 2-bar SD
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  5. #5
    Advanced Tuner MikeGyver's Avatar
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    2000 GMC 2500 2-bar SD
    Stock LM7, LTs, TBSS intake manifold

  6. #6
    Advanced Tuner MikeGyver's Avatar
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    When I first entered my two V/AFR into the list in scanner, instead of putting the .5 volt afr into the .5 v column, I changed the first entry from 0 volts to .5, and tried entering the 4.5 volt afr somewhere else wrong, too.
    When I did it the right way, it worked. Thanks.
    2000 GMC 2500 2-bar SD
    Stock LM7, LTs, TBSS intake manifold

  7. #7
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    what was the right way? I see two different tutorials

    http://www.hptuners.com/help/demos/custom%20EIO.swf

    When I use the tutorial I get this:

    (4.5-.5)/(20-9)
    4/11 = .3636

    SO I use that in the Volts box .3636 + 9

    Is that correct? Its done per the tutorial.





    and this thread and they seem to be different ??
    Last edited by 79 z28; 07-20-2014 at 02:01 AM.

  8. #8
    Advanced Tuner umrjmac's Avatar
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    I think I just responded to your other post

    The old AFX box would run 3 different voltages at startup representing min, max, and stoich voltage output. I don't know if the new ones do that, but if they do, it gives you a really easy way to check your transfer function to see if its right. You can also log the voltage value from that EIO input directly if you want to validate that it really is .5 and 4.5V for min/max as read by the device.
    Kenne Bell Supercharged 2003 Corvette Z06

  9. #9
    Advanced Tuner
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    Must have had a digit wrong or something... installed 2.24 and used the new PID and it seems to work fine now

  10. #10
    Tuner in Training
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    So this is the same for lamda? The 10-11 Camaro V6 tables are lambda, not AFR. So would this be correct?

    Wideband O2 Sensor (LC-2)
    0 Volts= .65 Lambda
    5 Volts= 1.65 Lambda

    Volts Max = 5
    Lambda represented by 0 Volts = .65
    Lambda Max = 1.65

    so 5/(1.65-.65) +.65
    or in our EIO Formula
    Volts/ 1 + .65