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Thread: Question on a 2013 GT

  1. #1

    Question on a 2013 GT

    2013 GT
    Boss 302 intake
    Kooks LTubes
    Ford Racing 47# injectors


    Why does it have 14.08 as a value for stoich and not an actual stoich value for gasoline?
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  2. #2
    Advanced Tuner Witt's Avatar
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    Quote Originally Posted by The Shop Inc View Post
    Why does it have 14.08 as a value for stoich and not an actual stoich value for gasoline?
    That's E10 Stoich which is pretty much standard across the country now.

  3. #3
    Maybe I'm not understanding how the fuel calculation works with the Ford stuff then. I assumed that the Stoich pid was the main fueling constant. SO if I command .85 lambda the desired afr would be 14.08x.85= 11.968. but the ecm closed loop corrects it to 12.5 as it would if the desired stoich was actually 14.6. Im asking as I am going to do an E85 tune and thought it would be like the GM stuff where I just change the stoich value but something is not adding up.

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    That's exactly how it works, multiply the the stoich value by the commanded lambda. How are you measuring a/f ratio? Also, any other fuel system mods such as BAP or otherwise?

  5. #5
    Quote Originally Posted by toyoguru View Post
    That's exactly how it works, multiply the the stoich value by the commanded lambda. How are you measuring a/f ratio? Also, any other fuel system mods such as BAP or otherwise?
    No other mods. Im measuring with my wideband in the left tail pipe. Shouldnt the Stoich value be 14.6? When tuning the MAF based on long/short term trims the a/f ratio shows 14.6+/-. So im confused why its correcting to "stoich" for gasoline when it has a value for e10 as "stoich"
    Ive looked at a couple tunes from the repository and they also have 14.08 as stoich.

  6. #6
    Advanced Tuner Witt's Avatar
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    Quote Originally Posted by The Shop Inc View Post
    No other mods. Im measuring with my wideband in the left tail pipe. Shouldnt the Stoich value be 14.6? When tuning the MAF based on long/short term trims the a/f ratio shows 14.6+/-. So im confused why its correcting to "stoich" for gasoline when it has a value for e10 as "stoich"
    Ive looked at a couple tunes from the repository and they also have 14.08 as stoich.
    Its not the car or tune that's the problem, its your wideband that's converting 1.0 lambda to stoich for pure gasoline. All o2s measure stoich, your wideband is converting 1.0 lambda to 14.7 pure gasoline stoich.

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    Quote Originally Posted by The Shop Inc View Post
    No other mods. Im measuring with my wideband in the left tail pipe. Shouldnt the Stoich value be 14.6? When tuning the MAF based on long/short term trims the a/f ratio shows 14.6+/-. So im confused why its correcting to "stoich" for gasoline when it has a value for e10 as "stoich"
    Ive looked at a couple tunes from the repository and they also have 14.08 as stoich.
    Because if your wideband is calibrated for straight gasoline, then your stoich will not jive with "true" stoich. The sensor doesn't know the difference, oxygen content is oxygen content, so if you don't have a wideband that can read lambda or a way to recalibrate the voltage versus AFR transfer function, it will always be a little off.
    Jaime

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    Quote Originally Posted by Witt View Post
    Its not the car or tune that's the problem, its your wideband that's converting 1.0 lambda to stoich for pure gasoline. All o2s measure stoich, your wideband is converting 1.0 lambda to 14.7 pure gasoline stoich.
    Witt treed me.
    Jaime

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    Bing, Bing, Bing....we have a winner in Electech. When calibrating, you should always have your sensors/meters reading in lambda. It'll save so much confusion with the variability of fuel, etc. The ECUs think in terms of lambda, as calibrators you should too.
    Jeff Chambers, Owner
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    Performance Parts, Service and Dyno Tuning Specialists

  10. #10
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    Looks like the others have helped you figure it out. And to reassert, the 14.08 is absolutely correct for running e10 (straight from almost any pump in the US). You should be able to swap the stoich value for e85 and go from there with tuning off of the lambda table For the fuel side of the tune.

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    Does this happen when using the factory wideband?

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    Quote Originally Posted by txcharlie View Post
    Does this happen when using the factory wideband?
    They should already read in Lambda.

  13. #13
    HPT Employee Eric@HPTuners's Avatar
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    The 13/14 (with in dash display) shows AFR based on the stoich entered into the PCM. So stock, if you command and get .85 lambda, the display will show ~11.9 AFR
    Eric Brooks
    HP Tuners, LLC

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    Quote Originally Posted by Eric@HPTuners View Post
    The 13/14 (with in dash display) shows AFR based on the stoich entered into the PCM. So stock, if you command and get .85 lambda, the display will show ~11.9 AFR
    Good deal! Thanks!

    So, to tune for e85, I would change stoich, injector data and add spark to take advantage of the added octane?

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    Quote Originally Posted by ElecTech View Post
    They should already read in Lambda.
    Thanks!