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Thread: setting B4105 O2 switchpoints to 450 with LT headers. Why do they say this?

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    Lifetime Member mvvette97's Avatar
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    Default setting B4105 O2 switchpoints to 450 with LT headers. Why do they say this?

    I have heard many people say to do this when you have headers but never understood why. Can somebody explain this and what is this doing with the O2s?

  2. #2
    Lifetime Member 5.7ute's Avatar
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    Setting B4105 to 450mv has the O2 sensors switching around this value when in closed loop. This basically is telling the pcm that a stoich condition is present when the narrowbands are reading 450mv under the current conditions (Which are set by the closed loop mode)
    Narrowband sensors are easily affected by heat, and can generate anything from 530mv to 400mv or so when a stoich condition is present.(rough approximation) Placing headers on the car effectively moves the sensor further away from the exhaust port so the sensor will run colder.
    Whether your sensor now runs at 450mv at stoich is something you will need to determine using your wideband while logging airflow during closed loop & comparing to the closed loop mode table.(B4107)
    The Tremor at AIR

  3. #3
    Lifetime Member mvvette97's Avatar
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    Ok I see. I changed my trans am to the 450 and it seemed to make it run in the 14.6 to 15.1 range, before it seemed to jump around alot more. I knew it done something "helped" but didn't really understand why. Thanks for clearing this up for me.

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