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Calibration differences, open exhaust vs. full exhaust

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  • Calibration differences, open exhaust vs. full exhaust


    I currently have the PF4 system installed on a Pontiac 428. It's been in service for about six months now and runs pretty well. My current exhaust setup is 2.5" from the headers, through magnaflow mufflers and out over the axles.

    I've been considering installing electric cutouts at the header collector flanges with dumps. My O2 sensor is installed about 6" away from the driver's side collector flange, on the header itself.

    If I do this, will it cause problems with the EFI system?


    Britt Bettell

  • #2
    Yes, would most likely create a problem but there's a work around. With the cutouts open you'll get a lot of fresh air contamination so the AFR will report as being artificially lean which will result in the ECU falsely trimming in a lot of extra fuel to try and correct what it thinks is a lean condition. You can go into the On/Off Options and turn Closed Loop off and the fueling will run off of the base fuel map plus your learned fuel values so assuming you've got plenty of learn time and everything is well trimmed (Short FT values less than +/-5%), the engine should probably run just fine in open loop. When you're done blowing out everyone's ear drums and close the cut outs. just turn Closed Loop back on. Just a finger touch away from sane to insanity.