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Thread: NO BOV discharge sound car seems slow

  1. #1
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    Unhappy NO BOV discharge sound car seems slow

    I have noticed something strange, got an HKS SSQV bov for real cheap, didn't try to install since I was planning to do it correctly with a MAFT, anyway, installed the bov just for a test it didn't blow, no sound at all, weird.. well did a boost leak test, found some leaks not too bad, replaced vacuums and Y pipe (plastic one was leaking), replaced the brake booster hose, it was cracked and didn't held any pressure, went for a test drive and the same, it was boosting like 7-8psi with the stock solenoid (aftermarket boost gauge, decent autometer one), even ran the car with the wastegates disconnected it easily hits 15psi (went for a quick drive just to see if one was stuck open) well I thought its defective, tried it on a friends RT/TT, everything stock and it's friggin loud! even at idle with some free revving, next we went to test drive and yeah its just loud, but I noticed something even stranger, car feels wayyy better, it pulls and feels like a Twin turbo V6 with some power, its just a stock car, not even a Boost controller, it was having fuel cut or spark blowout but still felt great, so definitely there is something wrong with my car, went and did the following:

    New gaskets, everywhere Lower Plenum set, intake manifold, TB.
    New injector seals/kit
    Rebuilt throttle body
    Tested with another BCS.
    Plugs.
    Swapped coils/PTU (not even a hint of ignition problem but worth a try)
    Compression test = about 150 all cylinders
    Fuel pressure is within specs (37 or something like that a @ idle)
    Timing is dead on
    Replaced the infamous rear turbo pipe Oring.
    Fuel Filter was replaced about a year ago, previous one came out pretty decent.

    Just to recap, the car didn't seem to have any problem, it was sitting because of a transaxle problem, got it fixed and I was really happy to drive it again until I went for a test drive with another TT and for comparison it felt like a sohc, lol.

    I did a few things, replaced the downpipe and didn't have provisions for the secondary O2 sensors so I got the usual CEL, also I got the EGR block plates, no EGR temp sensor, could this put my ECU into limp mode and make the car slow (it doesn't make sense to me because it should still make a pssh psh sound even with a low octane/timing map)

    Tired/worn engine? Got pretty good compression results.
    Bad turbos? No smoke or soaked pipes, gauge shows that they're building some boost.
    Bad ECU? Car works great just not sporty feel.
    Clogged cat/precats?


    What I could search for in datalogs to know if some sensor is defective, I know that a failing crank sensor wil make the car almost undrivable.

    Have a wideband and boost gauge, can datalog, pretty long post lol..

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    Tested the following:


    Block the Throttle body side, fill with compressed air, can easily pressurize up to 20psi, leaks down slowly and I can't hear any hissing.
    Remove each IC hose going into the Y pipe, block with bare hand, both generate boost and can push lots of air.
    Removed the wastegates lock pin and test for a fully closing flapper, both are closed and correctly open at about 6-7psi.
    Not a single hiss from the BOV, also tried another vac house, rear plenum port, noticed that it never fills up the intake manifold, tried blocking that port and its almost always vacuum there.

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    Quote Originally Posted by reses View Post
    Tested the following:


    Block the Throttle body side, fill with compressed air, can easily pressurize up to 20psi, leaks down slowly and I can't hear any hissing.
    Remove each IC hose going into the Y pipe, block with bare hand, both generate boost and can push lots of air.
    Removed the wastegates lock pin and test for a fully closing flapper, both are closed and correctly open at about 6-7psi.
    Not a single hiss from the BOV, also tried another vac house, rear plenum port, noticed that it never fills up the intake manifold, tried blocking that port and its almost always vacuum there.
    You switched the vac source for the BOV?
    Sounds like pretty much has to be either a boost leak or not a good vac source for the BOV.

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    Yes, I switched the vac source, used the rear FPR nipple, same deal, I noticed something, I'm gutting the precats and noticed that with my DP removed I can somehow build 5psi free revving, before I couldn't do that, I'm gonna finish that, reseal the oilpan gasket and go for a test drive, I used the same vac hose, port and source on another car (totally stock RT/TT) it sounds really loud.

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