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Thread: Rear O2 sensor (bank 1 sensor 2) + HFC, to disable or not

  1. #1
    Tuner in Training
    Join Date
    Jun 2022
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    17

    Rear O2 sensor (bank 1 sensor 2) + HFC, to disable or not

    Hello,

    As the title says, I am unsure if I should disable my rear o2 sensor. From what I was originally under the impression of was that the rear O2 sensor does not impact the cars performance. But after learning more and more I realize the rear o2 sensor takes in the data for the LTFT, which in the end will adjust the fuel trims, please correct me if I am wrong. Now with an after market HFC and a O2 sensor spacer, the readings that come through must be far off and skewing my fuel adjustments made by the ecu. Do you suggest disabling the sensor to prevent the false reading impact, if there is one?

  2. #2
    Advanced Tuner
    Join Date
    May 2014
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    USA
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    444
    Depends on the car/ecu.

    what's the car/ecu in question?

  3. #3
    Tuner in Training
    Join Date
    Jun 2022
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    2015 Audi A4 quattro B8.5 CPMB MED 17.1b. (CTS HFC w/ a spacer placed at rear 02, CTS IC, GFB DV+,)



    I have some run data from my base car file and then a tune I am slowly putting together from all the different examples and information out there. The LTFT looks off in both cases hence why I asked.

    Open to any and all advice.

    Base File 20220806_base_Run_3rdpulls.hpl

    Tuned File 20220806_Tune00A_Run_3rdpulls.hpl I guess this fuel trim data is not present bc I flashed the car and didn't run the tune long enough, as it was my first one, I was nervous to F IT UP.
    Last edited by Ark88; 08-11-2022 at 07:54 PM.

  4. #4
    Tuner in Training
    Join Date
    Jun 2022
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    So for my stage one tune I ended up just opening the acceptability range for the long term fuel trim data. This way when it is far off the ECU can self correct but wont be doing so constantly due to the over sensitive O2 sensor.

  5. #5
    if your still catted dp then i would keep them active. if your catless, disable them.