Engine help: major under boost
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This is a discussion on Engine help: major under boost within the Engine Modifications forums, part of the Tech & Modifying & General Repairs category; I logged my car today to see how stage 1 was going. I have a 2011 wrx sedan. From 2k ...

  1. #1
    Registered User ElusiveSAV's Avatar
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    Exclamation Engine help: major under boost

    I logged my car today to see how stage 1 was going. I have a 2011 wrx sedan. From 2k Rpms till 6100 Rpms I'm only getting 9lbs of boost. Target is 13-17. Tried running the high wastegate map and it did not help at all. All signs lead to boost leaks? Where should I look? I bought the car used. I don't believe there is any other work done. The downpipe still says Subaru on it. I would post my logs but I don't have Internet only my phone. All other readings are good DAM = 1, fine knock learn = 0. Could I be logging wrong? I was in 3rd and went from 2k till 7. 100% throttle. Wastegate duty readings are ranging from 65-71. Never was I even close to target boost. Help plz!

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    MAINEiac 11blackSTi's Avatar
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    Is it a cobb map? Any mods other than the flash? If I were you I would flash to stock and see how it runs on stock.

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    Registered User ElusiveSAV's Avatar
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    Just uninstall it and log it?

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    Registered User ElusiveSAV's Avatar
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    Yes Cobb map. Nothing else done that I know of.

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    Master Baiter EJ257's Avatar
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    Boost leak (check the TMIC/TB coupler)
    Boost control solenoid
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  7. #6
    Registered User ElusiveSAV's Avatar
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    How do I check it? See if its pushing air out?

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    Registered User Liquid2k's Avatar
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    Sounds like you're reading wastegate spring pressure... If you want an informative thread on how boost works on our cars, check out this link from cobb: https://cobbtuning.zendesk.com/entri...l-System-Works

    Also, here is a flow chart that you may find useful for troubleshooting your problem:

    My buddy just had the same issue with his STi, result was a missing restrictor pill in one of the lines from the BCS. I highly doubt flashing to stock will yield any helpful results.

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    Registered User ElusiveSAV's Avatar
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    So best way to combat the problem would be what?

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    zax
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    From where did that flowchart come?! I would absolutely NOT disconnect the wastegate plumbing to see if the boost spikes. This could easily blow the motor for a number of reasons: 1.) compressor outlet temps will be much higher if run out of efficiency... resulting in increased predet 2.) untuned boost pressures may put the car into untuned load cells, thus putting the spark event after the det line. Either situation will cause irreparable damage to the motor.

    If you suspect the solenoid, remove the solenoid and check the resistance on the test pins. Or, even simpler, put the car into test mode and listen for the solenoid to click.
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    Registered User Liquid2k's Avatar
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    Quote Originally Posted by zax View Post
    From where did that flowchart come?! I would absolutely NOT disconnect the wastegate plumbing to see if the boost spikes. This could easily blow the motor for a number of reasons: 1.) compressor outlet temps will be much higher if run out of efficiency... resulting in increased predet 2.) untuned boost pressures may put the car into untuned load cells, thus putting the spark event after the det line. Either situation will cause irreparable damage to the motor.
    I found the flowchart on another STi forum while searching for a solution to a friends problem. I completely agree with the dangers of disconnecting the wastegate line for a prolonged period, however, would you suggest it is still as dangerous for use in a very short duration? When I spoke with a Subaru tech about the issue, he said it would help to eliminate potential causes.. but warned that if boost levels were approaching target, to keep out of boost until returning home.
    .. Your input is appreciated Zax, so that I do not pass this information on if it is incorrect or dangerous...

  12. #11
    zax
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    IMO it's too easy to boost to dangerous levels.
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    Registered User ElusiveSAV's Avatar
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    Problem found. Previous owner had a EBC. Replaced with wrong lines and didn't hook some up. Thanks for your help! This should fix my problems. Vacuum lines from wastegate to turbo.

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    I just put an EBCS on my '13 this past weekend too. Made sure I followed each line from the unit to the correct connecting device. Very easy to pinch a hose with the angles. Glad to see you figured it out on your own.

  15. #14
    Registered User ElusiveSAV's Avatar
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    I had help from turbotec ray and Zax. Couldn't have done it without the help of this forum!

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    Subaru Newb MainFrame's Avatar
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    Quote Originally Posted by Liquid2k View Post
    ..would you suggest it is still as dangerous for use in a very short duration?


    A single uncontrolled overboost like that could easily kill the motor, turbo, or both.

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