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Thread: Solved. EJ208 not boosting properly.

  1. #1
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    Solved. EJ208 not boosting properly.

    Alright, I've recently acquired a BH5A Legacy with 95k on it for what I think was a pretty good deal. Reason being is that it isn't boosting properly, it sounds like a has pretty substantial boost leak. Previous owner is/was under the impression that the secondary turbo has given up. I'm not so sure thats the issue although it is possible and the primary is just blowing air through a siezed or real bad secondary.

    The car only makes about 5-6PSI. The VOD does not seem to occur unless I shift into it, then the car will drop to 1-2PSI before recovering back to 5-6PSI. There is some light oil residue in the charge pipes from both turbos, both appear normal from my experience with turbo engines.

    There is no check engine light.

    I've checked all vacuum lines, including the BBOD for proper routing against the diagrams found on this forum and also for obvious leaks, visually there is nothing wrong with them, they are routed correctly and are not brittle. Currently trying to find somewhere that can smoke test it or make something that I can make work myself, I don't have access to an air compressor so that might be tough...

    I do have some confusion around the lines from the primary turbo/wastegaste to the boost solenoid and the aftermarket GoFastBits BOV. There was a disconnected vacuum line there off the primary turbo intake pipe but no change after reconnecting. I think I could be looking at the line 10 mod but I'm not certain and the car was previously boosting correctly according to the previous owner so I haven't mucked with them.

    I have a line on some replacement turbos (VF25/VF27) current primary is a VF31 and haven't had time to get a read on what the secondary is. Replacing what I have with the 25/27 will be a bolt on operation and won't cause any issues correct?

    The car does seem to have a small exhaust leak, I can smell it but can't seem to locate it. Any suggestions on where I could find a replacement set of TT headers and all the associated gaskets for doing a header/turbo replacement would be much appreciated as I am struggling.

    Also doing the timing belt/idlers and water pump, waiting to hear back on a kit for that.

    What I'm looking to gain from this post is confirmation that I'm at least on the right track. Or if there are any suggestions on what lines/solenoids deserve a closer inspection, I'm listening!
    Last edited by MeatBird; 12-12-2023 at 09:44 PM.

  2. #2
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    step 1 - find the boost leak.

    Do a standard (smoke, etc) boost leak check first - it may be something simple like the shitty plastic intercooler inlet pipes or a loose clamp. I recommend throwing those pipes away, and using standard silicon bends of the appropriate sizes. You'll get better spool.


    If its not as audible as a 'usual' boost leak, two TT-specific things to check.

    1/ the IACV (intake air control valve) on the secondary. That's the big throttle-body like flap plate connected to the intercooler under the driver's side. That'll cause the primary boost to leak back through the secondary when in primary-only turbo mode.

    2/ the secondary PRV (pressure relief valve). That's a weird little plastic diaphragm valve under an upside-down u-shaped bit of pipe, located between the secondary outlet and intercooler. It'll cause secondary boost to leak back into the intake (post MAF). It's basically a bypass valve which is opened up during secondary spool.

    number 2/ wouldn't cause boost drop when on primary.

    6psi is almost (but not quite) wastegate pressure (~9psi?) - so make sure your wastegate is plumbed up correctly.

    Start here. Original link is dead, but the clubsub quote is still alive: https://www.clubsub.org.nz/forum/ind...to-twin-turbo/

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    Update.

    Timing completed, it was time.

    Turbos replaced. Replacement units appeared to be in good shape before install. Cannot rule out that they may still be part of the problem. My initial thoughts of boost leak on the old turbos may have been correct but are not what i suspect now as I have seen as high as 17 PSI on the gauge.

    BBOD lines cleaned/inspected and replaced quite a few.
    BBOD solenoids cleaned.
    Boost control solenoid cleaned.
    Line 10 from the manifold to the T into primary intake had a pretty bad cut, replaced but no change.

    Primary turbo wastegate works as it should.
    Secondary Pressure Relief valve doesn't leak, gonna figure out a way to confirm it is actually opening.
    IACV works as it should.
    ECV works as it should.
    Vacuum tank holds vacuum & will actuate IACV & ECV in daignostic mode.

    The issue I'm having now is that the car still will only make about 5-7 PSI on the primary, when the secondary comes on I see 15-17 PSI. HOWEVER the secondary doesn't sound right to me, best way i can describe it that it sounds like its really working and then less so. Kind of a SHH-sh-SHH-sh-SHH, a rhythmic on/off if you will, but boost remains stable while it is doing this.

    Then between 5000 and 5500 rpm boost will drop to about 2 PSI and remain there until letting off and coasting for a few seconds
    The car still runs smoothly when this happens, no bucking or hesitation, just no power. If i stay high in the revs it will do this again after the boost comes back.

    Car will occasionally throw code 66 if I stay on it after the boost drops but I don't typically because something is clearly wrong. If i stay out of secondary turbo range I can drive the car with no issues and the check engine light will stay off. This is the only code it has ever given me.

    Anyone have any ideas or experience with a similar problem?
    Last edited by MeatBird; 10-09-2023 at 12:16 AM.

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    SOLVED

    It finally got cold enough to see that the exhaust was only coming from the tiny gap between the silencer and exhaust tip. Turns out the fiberglass muffler packing came free and completely blocked the exhaust. Glad to have the car running right now but man, felt dumb for spending months chasing my tail on this.

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