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Thread: 2020 sierra commanded AFR VS ACtual Knowledge request please

  1. #1

    2020 sierra commanded AFR VS ACtual Knowledge request please

    Im trying to start tuning my procharged 20 5.3, but a little confused about commanded afr! The commanded stays at 14.1 at cruise but I have verified with two separate AEM gauges in either pipe that the truck runs at 14.7 at cruise! Am I missing something or is the AFR error really this bad and I need to correct it?

  2. #2
    Tuning Addict 5FDP's Avatar
    Join Date
    May 2012
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    Rogers, MN
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    They target 14.1 figuring you are running E10 fuels.

    If you are not running E10 fuel, change the stoich back to 14.68.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  3. #3
    They advised 93 only from ATI/Procharger, plus I noticed they disabled the Flex fuel from my stock file. So just change stoich to 14.68 and move along! Thanks

  4. #4
    Can you post tune file and log?

  5. #5
    They may have disabled flex fuel because you didn't pay them to tune on e85. Most companies charge more for e85 tune on top of pump gas tune

  6. #6
    Quote Originally Posted by GMCfast View Post
    They may have disabled flex fuel because you didn't pay them to tune on e85. Most companies charge more for e85 tune on top of pump gas tune
    Yeah we don’t have e85 readily available where I live plus I’m not racing it. Just a driver.

    I will post the file after I step down to another pulley and get my psi back up along with my tune back correct. When I removed the cats I lost around 1.3 psi and the MAF LTFT got a little out making her hunt a touch

    Having a little trouble though as these 2020s don’t have the maf min and max you can adjust to put it in maf only mode
    Last edited by jacob3318; 06-16-2020 at 06:55 AM.

  7. #7
    Quote Originally Posted by jacob3318 View Post
    Yeah we don?t have e85 readily available where I live plus I?m not racing it. Just a driver.

    I will post the file after I step down to another pulley and get my psi back up along with my tune back correct. When I removed the cats I lost around 1.3 psi and the MAF LTFT got a little out making her hunt a touch

    Having a little trouble though as these 2020s don?t have the maf min and max you can adjust to put it in maf only mode
    Do you know average ethanol percentage of the pump 93 AKI? It may be 5-10% ethanol so you may want to move back to 14.1 AFR or somewhere between 14.1-14.7. Just a thought

  8. #8
    Tuner in Training
    Join Date
    Jan 2008
    Posts
    45
    Your wideband is on a 14.7 stoich Gas scale or 1.0 lambda. Your computer is commanding 14.1 e10 stoich or 1.0 lambda. So basically if you switched your aem to lambda and looked at commanded eq instead on your scanner they will both be 1.0
    2019 Camaro SS A10
    Long Tubes, CAI, Ported lt2 intake, Ported TB, and Flex fuel.

  9. #9
    That makes sense sir thank you. I had changed my stoich to 14.7 in editor. I think I’m going to go back to 14.1 now. Let the ecm do its thing