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Fluttering noise when lifting off accelarator

Discussion in 'A3/S3 Forum (8L Chassis)' started by imported_alecblack, Mar 7, 2005.

  1. imported_alecblack
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    imported_alecblack Guest

    Can anyone tell me if this sound is meant to be there? I have a 1.8Turbo and when i am driving and lift my foot off the accelarator pedal i hear a light fluttering noise.

    Is this normal or does it sound broke?

    Its my first turbo car and im not sure if it is the turbo spinning or something worse.
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  2. imported_gek
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    imported_gek Guest

    I think it means your DV is knackered.
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  3. Grant
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    Grant Well-Known Member

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    Sounds like your diverter valve is knackered - common problem with OEM valve... they don't last that long.

    A new one will cost about £25 from Audi.
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  4. benk
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    benk Member

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    Yeah, agree - I noticed mine when I could hear turbo fluttering between gear changes. A new one should mean you lose the fluttering sound and get smoother gear changes as turbo pressure will be maintained instead of being lost when lifting off/changing.
    #4
  5. imported_alecblack
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    imported_alecblack Guest

    This has been happening since i bought my car 5 months ago, is this a serious problem, is it costly to fix, does it affect the performance.

    Sorry for the barage of questions but im a bit worried now.
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  6. s3bow
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    s3bow Member

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    I thought the fluttering noise is the turbo stalling because the air being forced into the engine hasw knowhere to go ( up against a closed throttle ). Probably won't damage yours but on bigger turbo cars with high boost can shatter blades.

    Chris.
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  7. benk
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    benk Member

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    Hmm, not sure: are you saying that because the valve starts leaking, it fails to open and divert pressure, thus keeping turbo pressure too high in the engine?
    Could be - anyone else want to chip in as to whether this can cause damage?
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  8. imported_alecblack
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    imported_alecblack Guest

    Would it be worth my while getting an uprated one. I am probably not planning on chipping it in the future, at most a K&N and a back box

    Is there any bhp increase in an uprated one? Or any other benefit.
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  9. s3bow
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    s3bow Member

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    Fluttering is def the turbo stalling. On low boost cars there probably won't be a problem though its not ideal. Fitted the forge valve myself and found it to be weaker than the standard one. Phoned forge and they sent me their 'yellow' spring. Def felt more responsive. But mine is a mapped S3. Not sure it would make a difference on regular boost.

    Chris.
    #9
  10. imported_Stewart
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    imported_Stewart Guest

    s3bow, if yours is mapped and running at least 1.1bar ish (bout 15-16psi at least) then i would try the blue or even the red spring.
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  11. HTC
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    HTC Active Member

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    s3bow, just to let you know, the fluttering sound is not the turbo stalling. Its the sound of the air through the faulty diverter.
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  12. s3bow
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    s3bow Member

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    Which one do you have ?

    Chris.
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  13. HTC
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    HTC Active Member

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    The valve is a plastic rubber diaphram. The diaphram can tear. It then leaks and flaps about as the air passes it.

    The throttle response issue is due to the valve inability to hold boost correctly when requested.

    Turbos stall when the pressure in the inlet track exceeds the force the rotors can supply. For example if the throttle flap is closed and the DV stays shut pressurising the area between the turbo and throttle body. This can happen, but if it is fluttering then it will be the torn DV.
    Turbo stalling is much louder.
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  14. s3bow
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    s3bow Member

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    I stand corrected .

    Chris.
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  15. imported_Gibbsy
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    imported_Gibbsy Guest

    I must say i disagree with most of what is said as i had this problem a while ago, bought a new DV from VAG parts, fitted it and the sound is still there.

    Now correct me if i'm wrong but surely it wont break as soon as i start the car.
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  16. leemclaughlan
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    leemclaughlan New Member

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    I thought the chattering was just the noise of the waist gate, heard mine more when i fitted an ITG pannel filter...

    I thought they were suposed to make that sound...It is it's job
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  17. HTC
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    HTC Active Member

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    [ QUOTE ]
    I must say i disagree with most of what is said as i had this problem a while ago, bought a new DV from VAG parts, fitted it and the sound is still there.

    Now correct me if i'm wrong but surely it wont break as soon as i start the car.

    [/ QUOTE ]

    Its difficult to diagnose turbo noises on the net. You may have had anything from a boost leak to a faulty N75?
    Generally its the DV, but obviously there are exceptions.
    #17

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