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Thread: 3 bar upgrade still only hitting 105 kpa

  1. #1
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    3 bar upgrade still only hitting 105 kpa

    On a C5 Corvette we installed a A&A supercharger kit. The car is still having a strange issue of dropping power at 5200 rpm like clock work. No misfires, the afr is on point and everything seems fine.

    Since it was a 1 bar map sensor we couldn't read the boost. We swapped over to a GM 3 bar sensor and updated the linear/offset to the according specs and we still max out at 105kpa. Is there anything else we need to change over to read higher then 105? We're trying to see if the car is losing boost at 5200 rpm.

    Anyone have any ideas about the power dip at 5200? It actually rebounds around 5500 and will pull to redline without any issues. Made 511rwhp
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  2. #2
    Tuning Addict 5FDP's Avatar
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    You are still logging the 1 bar MAP channel that only reads to 105kpa.

    Remove that and replace it with the 3 bar MAP channel.

    How come you didn't upgrade the OS to the 2 bar OS so you can tune the VE for boost?
    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
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    It's a low boost car and doesn't need a Speed Density tune. I'm just upgrading to a 3bar map sensor to see if the boost is falling off at 5200rpm. This car has been a major pain and I'm running out of ideas why this thing would magically loose power at 5200 and the bounce back like it does. It feels like a slight stumble but the fuel, seems fine, there are no misfires and I can't see any other issues in the scan.

  4. #4
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    When I go to look up map sensors in the scanner I'm only getting two options. One by voltage and one by boost. Nothing about 2 or 3 bar. Do I need to update the scanner?

  5. #5
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    You are logging the MAP sensor voltage, just make a user math to convert it to PSI. MAP sensor voltage * 9.06- 1.632. I see almost 22PSI MAP, so just under 7 psi boost at peak.

  6. #6
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    Theres a bump in the narrow band bank1 o2 sensor voltage, and in the wideband, that indicates a miss or blow out around 5200. What are your plugs gapped too?
    Last edited by murfie; 03-30-2020 at 02:29 PM.

  7. #7
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    They were gapped by A&A, brand new NGK's from the kit.

  8. #8
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    I would pull them and make sure they are gapped between .028-.030. If they are .035, that may be just a little too wide.

  9. #9
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    Gap was fine, changed the wires to and got the same results

  10. #10
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    Even if you re-poll for supported parameters there is still no 2 bar or 3 bar MAP channel to log?
    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.

  11. #11
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    At part throttle MAF is reading about half of the airflow I would have expected(maybe you are scaling). Yet its -32% stft and -18% LTFT.