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common underboosting causes?

Discussion in 'A3/S3 Forum (8L Chassis)' started by russwuss, Oct 26, 2013.

  1. russwuss
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    russwuss Member

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    Red hose decided to pop off on the S3 yesterday, loosing all boost.

    Just put it back on and the car still isn't boosting right, foot to the floor in 3rd it's doing 14 psi max.

    It's remapped stage 1, normally boosts to at least 20 psi and holds it all the way through 3rd.

    What's the common causes for underboosting? Need to investigate tomorrow...

    Thanks!
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  2. badger5
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    badger5 RIP S3dave Site Sponsor

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    stuck in limp mode?
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  3. russwuss
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    russwuss Member

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    Exactly what I thought.. But no, no fault codes what so ever.

    Took every silicone hose off, cleaned, checked for any hoses/splits and put all back together - still under boosting - then all of a sudden it started working again, was as if something was stuck and become dislodged.

    Since.. Red hose has popped off again (whilst having a play with a lotus Elsie :( ), looks like it's collapsing under pressure so I've gone for the forge hose and some JCS clips - hopefully that's the end of it :)
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  4. badger5
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    badger5 RIP S3dave Site Sponsor

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    collapse under pressure??
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  5. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator

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    Assuming turbo still ok. I'd look at the red hose again. They do split allowing boosts to leak away. You anywhere close to someone with a smoke tester ? Was it making full boost before it popped off?
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  6. russwuss
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    russwuss Member

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    Not sure on the technical word for it - the stock red boost hose is mis-shaped at the moment, it's extremely soft. So I was thinking because it's constantly changing shape it's cause the hose to come off the lip on the charge pipe.

    Forge one has turned up today so I'll give that a go tonight.
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  7. russwuss
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    russwuss Member

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    Yep was boosting perfectly fine.. then just stopped.

    I'll be fitting the new hose tonight which should fix the problem forever, will be smoke tested when I have enough funds to go Stage 2.......... however new MacBook came out so that's damaged the wallet recently :D
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  8. badger5
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    badger5 RIP S3dave Site Sponsor

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    they can tear internally.. and you can feel them oily on the outside as they seem to get porus etc
    If the charge pipes a little out of place it can twist the hose a little kinking it.

    you say no boost as in zero psi? do you have a guage in the car?
    wastegate stuck open, or missing? DV stuck open? wheels missing off the turbo? not sure how else it could be 0 psi boost if its 0 and not actuator 5psi (ish)

    weird
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