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  1. #1
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    lost boost after valve cleaning...

    So in a nutshell... Was boosting 17.5psi midrange falling to 14.2ish at redline. Went to dealer to get valves cleaned and left and with same tune now 17.5 midrange 12.49 at redline??? and it's consistant. My boost req and boost actual is like 3psi off now where is was good before. Did a boost leak test on just the mani and cold pressure pipe and all is good? Could cleaning the valves had made car not hold boost as well?? Cant figure it out. Wastegate after PID 5k rpm and up is 57% so wastegates are closed.. Any thoughts guys??
    7 335i 6mt cobbAP+fbo+e85 12.9@112mph so far
    06 c6 vette- sold 13.0@114.5mph
    06 evo9- sold 11.5@123
    10 genesis-sold slow
    04 srt-4-sold 11.6@126mph

  2. #2
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    I'd recheck the torque specs for the intake manifold to the head. Also ensure that they replaced the gaskets. A deteriorated gasket can easily cause a boost leak at WOT.

    Log WGDC and see if it has increased significantly.

  3. #3
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    Boost leak checked the mani no leaks. Maybe some of the walnut shell ruined turbine?
    7 335i 6mt cobbAP+fbo+e85 12.9@112mph so far
    06 c6 vette- sold 13.0@114.5mph
    06 evo9- sold 11.5@123
    10 genesis-sold slow
    04 srt-4-sold 11.6@126mph

  4. #4
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    Click here to enlarge Originally Posted by sharptech Click here to enlarge
    Boost leak checked the mani no leaks. Maybe some of the walnut shell ruined turbine?
    If the did the process properly it's shouldn't go through to the combustion chamber. Remember that boost is a measurement of resistance so a drop in boost does not mean a drop of air flow. Dyno the car and see what the power is like.

  5. #5
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    Actual boost numbers are rather irrelevant. What matters is boost vs. boost set point. If it's below set point, you have a hardware or tuning issue. If the set point is below your expectations, you have a tuning issue.
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    Check before and after wgdc, 57 after pid seems very high. What's wgdc bank? Theoretically boost could drop due to flow, as George said... Were you also maxing dc before the cleaning?

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    Click here to enlarge Originally Posted by Tzu Click here to enlarge
    I'd recheck the torque specs for the intake manifold to the head. Also ensure that they replaced the gaskets. A deteriorated gasket can easily cause a boost leak at WOT.

    Log WGDC and see if it has increased significantly.
    An intake gasket leak will cause a rough idle as it is a vacuum leak....plus BMW makes them pretty tough, havent seen one fail yet....

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    1 out of 1 members liked this post. Yes Reputation No
    Similar thing happened when I had the dealer clean my valves as well. I fixed it by removing the diverter valves from all four ports and cleaning a bunch of dirt and walnut shells that weren't allowing them to seal properly. Also when diagnosing the problem I found the vacuum line that runs behind the oil filter housing had broke and someone used a larger piece of tubing as a coupler instead of replacing the whole line. Once I cleaned the DV's my boost was back to normal, and I had the dealer fix the vacuum line. I was throwing codes though and the car would barley hit 8psi, but after cleaning the dv's I was back to 18psi. Hope that helps!

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