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  1. #1
    Active Member One Ring
    Join Date
    Mar 07 2016
    AZ Member #
    369903
    Location
    Charlotte, NC

    Overboost delete

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    Greetings to all. I'm a new (new to me) A4 B6 1.8T owner looking to have some fun with this car. I have deleted the N75 valve and installed a MBC which is pretty cool but prior to getting the MBC adjusted properly the car would go into limp mode as expected. After thinking about it, I'm curios to know how are the guys that are running 20+PSI of boost getting around going into limp mode. I'm aware of 'The Diode' mod but I'm assuming they have a reflashed ECU that has removed that safeguard.
    Am I correct?

    Thanks,
    E

  2. #2
    Veteran Member Four Rings Seerlah's Avatar
    Join Date
    Dec 05 2007
    AZ Member #
    23104
    Location
    A place between here and there

    Dude, don't just remove the n75, install an mbc, crank up the boost and expect things to be ok. People who run more boost are tuned for it. What you are doing is essentially introducing too much air to the system with no tune (fuel or ignition timing) compensation. In a nutshell...you are forcing a lean condition on your car when you boost past what the ecu is expecting to see.

    A tuned ecu has an actual map change with proper fueling and advanced ignition timing. This is what prevents limp mode...an actual tune.
    I hate it when my car acts like a little bitch, treating me like a bitch

  3. #3
    Active Member One Ring
    Join Date
    Mar 07 2016
    AZ Member #
    369903
    Location
    Charlotte, NC

    Yes I realize I cant crank it up and expect the best. I try to read as much as possible about our engines and ECU's to learn as much as possible. I know tuned ECU's have adjusted fuel and ignition maps but it will still see an overboost unless that function of the ECU is either removed or the parameter raised. Correct?

  4. #4
    Veteran Member Four Rings Seerlah's Avatar
    Join Date
    Dec 05 2007
    AZ Member #
    23104
    Location
    A place between here and there

    Yes, the paramater is raised. ECM is fully tuned to accomodate for the added boost. Instead of the ECM requesting 11psi stock (7psi AEB), it will be requesting 21psi (common OTS tune setting for 93 pump gas). The way you do it by just dialing the boost up, the ECM is still requesting 11psi. You are adding way too much air and cause pre-detonation once the ECM retards ignition timing. Not safe for your engine at all and can (or will) damage it.

    Best option is to just spend the money for a proper tune, put the n75 back, upgrade your diverter valve (710n from the TT225 is the more cost efficient route), upgrade your spark plugs to accomodate, and enjoy a safely tuned vehicle that won't cause damage.
    Last edited by Seerlah; 11-25-2018 at 11:08 AM.
    I hate it when my car acts like a little bitch, treating me like a bitch

  5. #5
    Active Member One Ring
    Join Date
    Mar 07 2016
    AZ Member #
    369903
    Location
    Charlotte, NC

    Cool. Thanks for the info and recommendations.



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