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Thread: back fire on letoff

  1. #21
    Tuner in Training
    Join Date
    Sep 2021
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    46
    Dude! I was going to post yesterday but got busy. Turned out mine had the original orange flapper from my intake's check valve stuck in the other check valve at the turbo inlet! So it couldn't pass enough positive crankcase pressure under high boost. Cleared it out and boom, no more smoke after let off. Sounds like the same problem you had. I saw that PCV fix you did on YouTube, I was contemplating it. Maybe in the future when I get the meth injection and turn the boost up more.

  2. #22
    If that orange valve is not in there anymore you need to do the updated pcv now. Without that valve your loosing pressure in the intake into the crankcase and the vent tube that runs to the turbo will cause some loss too by pulling air out of the intake instead of the crankcase.

  3. #23
    Tuner in Training
    Join Date
    Sep 2021
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    46
    Yeah I actually replaced the intake and did the PCV fix on it. The plunger was stuck in there from the original one! Crazy it has bean stuck basically the whole time I have had the sonic. Lol. Thanks for the heads up though brother, appreciate that.

  4. #24
    I changed timing, fuel, throttle pressure and wastegate bov (not all at the same time), now when I pull hard and let off with short pause before hitting it again it lag's some before it pulls hard again, any thoughts? 1.4t 2012 auto it has 2 final drives trans and secondary final drive for IRS 6.14/1

    [ATTACH]122709[ATTACH

    950 ; current shift, torque and WOT setting.hpt
    Attached Files Attached Files
    Last edited by carotene; 07-25-2022 at 11:04 AM.

  5. #25
    Tuner in Training
    Join Date
    Sep 2021
    Posts
    46
    Probably just losing boost and has to spool up again. Other then that maybe pressure delta setting isn't allowing it to increase pressure fast after let off. Does the WG close fully (max duty cycle) while it's building back up, or is it gradual?

  6. #26
    The back fire on let off is back, I'm not sure it was gone at all. I have changed several things trying to fix but so far no change. This is the tune now anybody got an idea what I might try next?

    950 ; current shift, torque and WOT setting.hpt

  7. #27
    Quote Originally Posted by Simplyjesse View Post
    Probably just losing boost and has to spool up again. Other then that maybe pressure delta setting isn't allowing it to increase pressure fast after let off. Does the WG close fully (max duty cycle) while it's building back up, or is it gradual?
    How exactly does the pressure delta factor work? I have noticed on my new bigger turbo, at any RPM, the ECU never closes the wastegate fully even when the requested MAP is 250 kPa, and current is like 100 kPa.