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ajq low boost

Discussion in 'A3/S3 Forum (8L Chassis)' started by kkk, Sep 28, 2013.

  1. kkk
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    kkk Member

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    Just fitted my boost gauge and only getting .4 bar but no codes and pulls ok, any ideas?

    Doesnt missfire and I thought all was ok till I see im only boosting half what its supposed to:/
    Changed loads of bits aswell.

    Did find a mbc under the scuttle all disconected but may of been used by the previos owner, could the pipes be the wrong way? Which is strange cause I think they all got the standard clips still.

    Thanks
    Last edited: Sep 28, 2013
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  2. kkk
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    kkk Member

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    checked and all pipes are the correct way, no visible probloms and i cant check my n75 with my basic vagcom.

    would i get away with hooking up the mbc in the actuater line to see if its the n75 stuck open?

    im stumped
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  3. kkk
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    kkk Member

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    just put 12v onto the n75 and its energizeing, could it be broken inside and not moving? iv never dismantled one.

    iv put the mbc on so i can see if it will make normal pressures if it does il replace the n75 i think
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  4. kkk
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    kkk Member

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    bit more info. with the mbc fully in or fully out, its a bleeder type i think, makes no difference, car is driving exactly the same as it was with the n75 so no difference what so ever which is my biggest suprise.
    i ran a quick log and showed 142.39 g/sat one point but still .4bar boost :/ strange no spikes or anything just flat like actuater pressure, but still 177 bhp working from the g/s

    i am seriously baffled, if it was a boost leak dropping it to .4 bar id surely hear it or hear my turbo screaming it tits off.

    the 142 was at 4760 rpm and 100% throrrle and 10.5 ignition angle
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  5. badger5
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    badger5 RIP S3dave Site Sponsor

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    if you remove the pipe to the actuator, and CAREFULLY went onto full throttle, what does it do
    CAREFUL, as this is No Boost control at all, and will if healthy shoot up very high boost.
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  6. kkk
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    kkk Member

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    i didnt want to try that but thinking i may need to just to rule it out but thought id ask for advice first
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  7. kkk
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    kkk Member

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    im scared lol, i dont want to run it disconnected. it builds boost pretty quick and does feel quite quick.im gonna try and check my gauge somehow
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  8. badger5
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    badger5 RIP S3dave Site Sponsor

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    if its builds boost higher than you had before, then the n75 is'nt working properly to control...

    you only need to run it to check it will produce more boost than it otherwise does and see how it spools..
    mbc if you have one to cap its overshoot would be safer if you are worried
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  9. kkk
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    kkk Member

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    il give it a try
    thanks
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  10. kkk
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    kkk Member

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    i ran it disconnected and its exsactly the same but still feels quick witch is baffling but like the turbos got a limiter on it lol, its spins up and i hear a dump but just wont boost any more.

    is this a dead turbo? :(
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  11. kkk
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    kkk Member

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    Before I buy another turbo is there anything else it could be?

    Thanks
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  12. badger5
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    badger5 RIP S3dave Site Sponsor

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    you hear it dump? N249 connected yea? dump would be DV being opened by an ecu which is intervening
    fault codes?

    check actuator has some preload and not looses as....
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  13. kkk
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    kkk Member

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    Yep hear a little dump, n249 deleted no codes at all except abs pump and ecu cant intervene with actuator disconnected can it? I can go flat out with it disconnected and no more boost :(
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  14. kkk
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    kkk Member

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    Im finding it strange that it will flow 142 g/s at .4 bar on a k03 so if it was .8 bar would be flying even more
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  15. kkk
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    Oh and the dump is only when I let off as it should, not just random whilst accelerating or anything
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  16. kkk
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    Feeling abit red faced right now but for no reason till I drive it. Checked the actator and has plenty of pressure on it, gave all the pipes another good going over and twisted a few clips and to my suprise the clip arond the pcv valve under the inlet just twisted around :/
    Think I may have found the problom or I hope I have and I hope I havnt destroyed my turbo whilst doing so.
    Will report back after iv drove it


    Thinking on... Would it not throw a code if it had that much of a leak? And I would of thought id of heard a leak that big if its been leaking


    Thanks Bill

    Neil
    Last edited: Sep 30, 2013
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  17. kkk
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    Was definitly a leak from there but not my problom I dont think, I can hear it dump abit louder now on light throttle cause of the mbc in there lock down so still no boost control and still the same, same performance same boost.

    Now the car definitly feels ok to drive and performance isnt to bad to be fair but I cant get my head round this max boost .4 bar regardless of boost control and even lack of :(

    Im running out of things to check, next il be unbolting the tip to check the turbo paly but surely if it was the turbo it would sound bad or drink all my oil or something :/
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  18. kkk
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    kkk Member

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    no body got any other ideas? surely someone has a clue?

    summery... low boost, no leaks, no codes and no different with the actuator disconnected, plenty of spring back on the actuator aswell
    and wont boost over .4 bar with no apparent running issues, its not limp as its all the time.

    so no experts here can help either :/

    im stuck
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  19. kkk
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    ok reading up iv checked my dv, when i push the piston up and block it with my finger the piston doesnt stay up but it clicks back down when i release it, is that about right? and iv tried blowing down each port and seems ok.

    i just want my car to be sorted so i can forget about things and just drive it :(
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  20. badger5
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    piston dv if not OE then yea, it wont stay up with finger on the end but it will stay up half way and when release it will click.

    if you have tried all of this and are sure there's no big leak hiding somewhere (smoke test ftw) then my guess is your turbos goosed..

    if with nothing connected to the actuator it still has no boost, its leaking internally via cracks, or the turbine is'nt spinning fast enough because its damaged or the compressor wheels also damaged, or wastegate penny is not shut or if it is its not sealing as it should bleeding the boost out immediately.

    none of this being good news of course
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  21. kkk
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    Is thereany way to smoke test it myself? Im in north London and cant find anyone that knows what im on about :/
    I might just make a normal pressure tester and see how I go. If it is the turbo then iv got the decision of wait and get the k04 bits togeather of just find another cheap k03 but being that its such a pig to replace I want to rule it out completly. But if its leaking internally I wont know will I?

    Thanks again bill shame im not nearer you :(
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  22. kkk
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    right, another little update, iv just pressure tested my system myself upto 1 bar and guess what, no leaks except a small one from between the pcv Y pipes, possibly the rocker gasket or the hose clips but any way, not enough to cause this 'low boost' lol.

    i went into the car whilst it was coming out slowly from the minor leak and the gauge was sat on .3 bar.

    i disconnected the gauge and tried pumping air down the small vacuum hose and even with the pressure spike it didnt go over .5 bar.

    so i think untill i can find a decent gauge to check with im thinking there isnt even anything wrong :/

    anyone got any experience with these?

    VW POLO GOLF BORA PASSAT T4 T5 SMOKED TURBO BOOST GAUGE | eBay

    thanks again for the help bill.
    #22

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