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Thread: Ecotec O2 Sensor Deletion...

  1. #1
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    Ecotec O2 Sensor Deletion...

    As I understand, the fuel mixture occilates up and down somewhat with 14.7 being the avarage, which provides fuel and oxygen for the catalytic converter. If the catalytic converter is removed the second oxygen sensor is disabled so as not to throw a check engine code. My question is: When this is done, does the mixture then go flatline? Like I would assume that it should? Or does it keep dumping unburned air and fuel into the exhaust for the now missing catalytic converter to not use?
    I've not found a satisfactory answer to this anywhere.

  2. #2
    Tuning Addict 5FDP's Avatar
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    The lean/rich swing is not just for the cat, it's for everything. The computer wants to target the stoich fueling no matter what unless a different commanded value is requested. Like for power enrichment or cat over temp protection in some computers.

    You want the primary upstream O2 to always be switching lean and rich of stoich to give you good drive ability and fuel economy. If there really was a lot of unburned fuel going through the exhaust, a cat wouldn't last long. It would go into meltdown pretty quick.

    If you remove the rear o2 sensor and cat converter, disabled the codes and disable the COT settings if there are any. That is all you need to do for that. It's not going to cause any major issues as far as I am aware.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

  3. #3
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    Thumbs up

    That's the first complete answer I've heard on this.
    The second part of the exhaust related question is:
    This build has long tube headers.
    20190624_090505.jpg
    What would have to be changed to accomidate the extra time it would take for the exhaust gasses to hit the still being used first oxygen sensor?

  4. #4
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    Look for something labeled transport delay or integrator delay
    JTC Performance - Authorized HP Tuners Reseller
    Performance Tuning in the Texas Panhandle

  5. #5
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    This is a 2.4 LE5 swap with custom built long tube headers as shown in photo above. I assume I will be needing a non-stock wideband upstream O2 sensor in order to tune correctly? Any recomended brand/part # etc. Any issue for the PCM to read a wideband when the original stock item was narrow?

  6. #6
    Tuning Addict 5FDP's Avatar
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    Swapping sensors like that is not an option. If can't read a wideband sensor when it was never designed for that purpose.

    Buying a separate wideband sensor and welding a bung into the exhaust is required. Then mount the gauge somewhere and wiring the wideband to work with HP Tuners via the PRO interface or another way like a 5v circuit on the computer with a custom channel made to log it.

    Tuning will have to be done with the computer set to run in open loop with the o2 sensor disabled, closed loop and fuel trims disabled. The custom channel you created will be what you log the commanded lambda/AFR against the actual Lamda/AFR to get your error percent. That error amount is then put towards the airflow model to correct the fueling.

    Confused yet?
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

  7. #7
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    I suspected something like that. Adding an extra bung is not a problem. (I built the exhaust myself) If the stock O2 sensor is disabled for the test, can I just remove it and use that bung? Or does the wideband stay in after everything is dialed in? What would it be connected to besides a gauge if it stays?
    Engine is naturally aspirated and will be used for long highway trips, so I'm looking for economy and longevity. Do I need to modify beyond the scope of the stock O2 sensor to achive this?

  8. #8
    Tuning Addict 5FDP's Avatar
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    Installing the wideband where the stock o2 is for calibration purposes is okay, many do that. I just always had the wideband installed and it stayed in all my vehicles. It was always good to know that it's running the way I wanted it and if something weird came up I'd be able to see it even without my laptop on me.

    Being that you aren't going for all out power, the wideband should be used just as a tool to make sure it's running how it should with the changes you have made. Making sure it can hit it's target fueling as commanded. You'd notice how far it was off if you let it run with the stock o2 sensor prior to changing anything. The fuel trims would show you where it needs work.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.