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Thread: Problem with TPS% reading 30 at idle

  1. #1
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    Problem with TPS% reading 30 at idle

    Hello all,

    im having an issue with my TPS% reading 30% at idle.
    It also reads 204% at pedal to the medal.

    heres my info:
    -AMC 304 V8
    -using 5.7L throttle body with 65lb/hr injectors
    -1227747
    -$42
    -IAC is 18 steps
    -TPS voltage is .57V
    -idle 800 RPM
    -open loop idle AFR 13.9
    -elevation 5000'
    -using 42.xdf from tunerpro's website.

    I pulled the power to the system overnight, but nothing changed. Is there something I'm missing?
    Last edited by AlpineCJ5; 02-22-2015 at 09:32 PM.

  2. #2
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    IIRC, to read TPS% correctly with a 7747, there is a datastream value that needs changed.

    TPS voltage seems fine, so nothing odd there. the TPS% value shouldn't be capable of displaying above 100% though.
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


  3. #3
    Super Moderator Six_Shooter's Avatar
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    TPS percentage is not a native part of the '7747 datastream, and ADX values are usually a fudged range that doesn't always work out to be accurate.

    The only TPS value that is in the '7747 datastream is TPS voltage.

    IIRC Mark had mentioned that there was a change that could be done in the bin to send out a proper TPS percentage value but it still wasn't 100%correct, just closer than trying to manipulate the TPS voltage value.
    The man who says something is impossible, is usually interrupted by the man doing it.

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    Quote Originally Posted by Six_Shooter View Post
    TPS percentage is not a native part of the '7747 datastream, and ADX values are usually a fudged range that doesn't always work out to be accurate.

    The only TPS value that is in the '7747 datastream is TPS voltage.

    IIRC Mark had mentioned that there was a change that could be done in the bin to send out a proper TPS percentage value but it still wasn't 100%correct, just closer than trying to manipulate the TPS voltage value.
    great info! I figured it was simply a calc based on TPS volts, but it didn't make sense how it could be so wrong.

    so knowing this, how should I tune stuff dependent on TPS%? for example, I'm tuning my PE circuit now, Is it okay to tune PE by offsetting MIN TPS% for PE by 30%? So I'd set PE to 100% instead of 70% for a true 70%.

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    Super Moderator Six_Shooter's Avatar
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    Ignore TPS % in the ADX, it's not valid.

    I can't give you any solid answer on how to tune parameters that use TPS %, other than feel and trial and error. You can guestimate what the TPS percentage would be, based on volts, and the pedal under your foot.
    The man who says something is impossible, is usually interrupted by the man doing it.

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    Quote Originally Posted by Six_Shooter View Post
    Ignore TPS % in the ADX, it's not valid.

    I can't give you any solid answer on how to tune parameters that use TPS %, other than feel and trial and error. You can guestimate what the TPS percentage would be, based on volts, and the pedal under your foot.
    Alright. This is what I'll do. Thanks guys!

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    There should be no need to guess or do manual calculations. Try editing the adx to get what you want. In the editor you find it under the Values. Basically, the TPS Volts and TPS % should be the same on the General tab except for the upper range and alarm (5 vs 100) but the formula on the Conversion tab would change to scale it differently. I believe the raw data goes from 0-255 for 0V to 5V. Once you open the adx editor and take a look it should be fairly clear how you can edit it.

    Or, try the file from this site and see if it works to give you what you want,

    http://www.gearhead-efi.com/Fuel-Inj...2&d=1375131735

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    Super Moderator Six_Shooter's Avatar
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    Quote Originally Posted by lionelhutz View Post
    There should be no need to guess or do manual calculations. Try editing the adx to get what you want. In the editor you find it under the Values. Basically, the TPS Volts and TPS % should be the same on the General tab except for the upper range and alarm (5 vs 100) but the formula on the Conversion tab would change to scale it differently. I believe the raw data goes from 0-255 for 0V to 5V. Once you open the adx editor and take a look it should be fairly clear how you can edit it.

    Or, try the file from this site and see if it works to give you what you want,

    http://www.gearhead-efi.com/Fuel-Inj...2&d=1375131735
    There's one huge flaw with that idea, TPS voltage never goes to 0, even at idle, so any conversion done on the TPS voltage is going to be incorrect. Even adding an offset does not work properly. I tried for a good long time to get an accurate TPS % on a '7747, but never got it close enough to be useful.
    The man who says something is impossible, is usually interrupted by the man doing it.

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    I'll try this tonight! Thanks for the pointers.

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    Does that PCM have an internal %TPS value? If yes, how do the 0% and 100% values get set? For example, does a routine use closed throttle voltage to set 0%?

    At any rate, I wouldn't call it a huge issue. That number will be closer than guessing based on your foot position....

  11. #11
    Super Moderator Six_Shooter's Avatar
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    Quote Originally Posted by lionelhutz View Post
    Does that PCM have an internal %TPS value? If yes, how do the 0% and 100% values get set? For example, does a routine use closed throttle voltage to set 0%?

    At any rate, I wouldn't call it a huge issue. That number will be closer than guessing based on your foot position....
    That's the thing the internal calc stays internal and It's not fed to The ALDL datastream. Trust me guessing will be As accurate as trying to calculate based an incorrect formula from TPS voltage. Although If you go back and read what I wrote, you'll see that I suggested oobserving the TPS voltage along with knowing where your foot is.

    Another part of the problem It's that you might be able get what seems like an accurate range on one vehicle probably won't be on another. The '7747 does not auto calibrate the TPS at start up like newer ECM/PCM do.
    The man who says something is impossible, is usually interrupted by the man doing it.

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    Observing the TPS voltage (which is already a scaling of the raw value) and figuring out what %TPS it is or just scaling the raw value to show as percentage do the same damn thing.....
    Last edited by lionelhutz; 02-23-2015 at 03:41 PM.

  13. #13
    Super Moderator Six_Shooter's Avatar
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    Quote Originally Posted by lionelhutz View Post
    Observing the TPS voltage (which is already a scaling of the raw value) and figuring out what %TPS it is or just scaling the raw value to show as percentage do the same damn thing.....
    No, no it's not.

    The TPS voltage != TPS %

    The TPS rests at between .4 and .56 volts IIRC , and at WOT will range between 4.5 and 5 volts, both of which are a pretty large range of discrepancy.

    .4 volts != 0.

    4.5 volts != 100%, when 5 volts can also be WOT.

    There is a vast difference between TPS voltage and TPS % as reported by newer ECMs, and is not based on the same ADX value.

    As I have already stated the '7747 does not report TPS % through the ALDL datastream, it only reports voltage. I believe there is a modification that can be done to the bin to enable the internal TPS % scaling to be reported on the ALDL datastream, but it is NOT something that happens in OEM form.

    Newer ECMs, such as the '7730 (and all codes that run in it) will auto calibrate the TPS voltage to 0 at start up even though the TPS voltage is not at zero, typically, like the '7747 between .4 and .55 volts, though I have not seen below .48 volts personally (at least not without a TPS error being reported). The '7747 does not do this.
    The man who says something is impossible, is usually interrupted by the man doing it.

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    It'll just be an approximation. You are recommending to watch voltage and guess at the %TPS because just throwing in a calculation to get a direct approximation of the %TPS isn't good enough? What the fuck is the difference?

    There is no %TPS. You have to basically make a best guess at it. The easiest way is to throw a calculation into the adx file and get a number. It won't match exactly what that ECM is using internally but it's at least an easy starting point. There, does that suit you?

    Now you're throwing in arguments about how newer PCM's work, which have no bearing on using a '7747....
    Last edited by lionelhutz; 02-23-2015 at 04:05 PM.

  15. #15
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    Quote Originally Posted by lionelhutz View Post
    It'll just be an approximation. You are recommending to watch voltage and guess at the %TPS because just throwing in a calculation to get a direct approximation of the %TPS isn't good enough? What the fuck is the difference?

    There is no %TPS. You have to basically make a best guess at it. The easiest way is to throw a calculation into the adx file and get a number. It won't match exactly what that ECM is using internally but it's at least an easy starting point. There, does that suit you?

    Now you're throwing in arguments about how newer PCM's work, which have no bearing on using a '7747....
    Look, I've used the '7747 quite a bit, I've tried a lot of things, one of which was to get an accurate TPS % value in the datalog. After many, many attempts to get something that was even a good approximation, nothing ever was, not even close. Changing the formula, adding removing offsets, etc. It was pointless in the end.

    To understand how TPS % output works, referencing other GM ECMs is most certainly valid, to contrast how things work, to help further explanation, since it seems that you only have experience with newer ECMs that have this ability built in.

    Keep it civil, or you will be taking a break from the site, we try to keep things nice here and don't tolerate hostility.

    I'm trying to explain things to you nicely, but you don't seem to be able to grasp that it's just not as simple as you believe. I too thought that it would be simple to put a formula in manipulating the TPS voltage, but after attempting it myself (going against what other people had said), I confirmed that it's just not that simple.

    So in your recommendation, when the throttle is closed and you get a TPS% value of around 12%, how is that helpful? Ok add an offset, now the rest of the range is off, reading low, because you have to take away what ever it was over at the beginning. So now change the formula, oh wait, now the offset is wrong, readjust that, and the range is off again. So now we look at the other end of the scale, and see that it's not reading 100% when the throttle really is, play around with the formula to get that right all while trying to get the other end to stay the same and hoping that the scaling through the middle actually works as well...

    Go and play with it if you want, I won't waste my time any more and will not recommend to anyone else to waste their time trying to set up a TPS % value based on the stock ALDL datastream of the '7747, it's an exercise in futility. If if someone was to get a TPS % value that worked right for that truck at that particular point, then the TPS needs adjustment or replacement, the whole process starts all over again.
    The man who says something is impossible, is usually interrupted by the man doing it.

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