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Turbo 'Flutter'

Discussion in 'A4/S4 forum(B5 Chassis)' started by NineNails, Sep 21, 2010.

  1. NineNails
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    NineNails Proud sponsor of the snack food industry

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    [Sep 21, 2010]
    Hiya
    Just started noticing I'm getting some turbo flutter on gear changes on my 1.8t and I'm sure it didn't used to do that. I've heard this flutter is a bad thing? So is there a problem and what's causing it? wastegate? or is it nothing to worry about and leave it alone?
    Thanks for any help
    Si.
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  3. tdia4
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    tdia4 TDIPOWARRR

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    [Sep 21, 2010]
    Have you recently put a cone filter on it? Could of been you just couldnt hear it before because of standard airbox, I had this problem on my old golf, turned out the standard recirculating valve was knackered and thats why it was fluttering, i changed it for a forge recirculating valve and it stopped doing it. Could just be a pipe that has come off it though or something like that.
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  4. evilscotsman
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    evilscotsman Space Cowboy

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    [Sep 22, 2010]
    if its fluttering, the dv isnt recircing mate, you would hear the tshhh of the dump with a cone filter on the 1.8T, as the dv vents so close to the maf. Flutter is the blades chopping thru reversing compressed air that's bouncing off the closed throttle plate, causes shock waves through the turbo which can damage the blades or twist the shaft, if nothing else it slows the turbine rapidly down below its "stall" speed, if the pressure is not let go when the throttle closes between gears. See if you can blow through the valve when power is applied to it. Sounds like its jammed shut.

    If its just a bit of flutter before the valve dumps, it may just be sluggish.
    Last edited: Sep 22, 2010
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  5. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Sep 22, 2010]
    Its probably what every chav in the country calls "Wastegate Chatter", which is infact compressor stall, and bugger all to do with the wastegate.

    As Evil says, its caused by the compressor "chopping up" air thats backed up inside the inlet, usually as a result of a broken dump valve.

    Stick a new 710N on there and hopefully that will cure it.
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  6. NineNails
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    [Sep 22, 2010]
    Thanks for the replies chaps. Would any of you have the part number for the 710N because I can't rely on the intelligence of my local Audi parts dept. Also, is it ok to continue to drive the car like this or is my turbo about to fly apart?
    Sorry for all the questions but this is my first turbo Audi and I'm doing my best to get my head round how it all works.
    Thanks
    Si.
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  7. voteforpedro
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    voteforpedro Member

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    [Sep 23, 2010]
    06A 145 710N
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  8. NineNails
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    NineNails Proud sponsor of the snack food industry

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    [Sep 23, 2010]
    Cheers for the part number, ordered today for £30.57 inc vat.
    Last questions (promise) What size jubilee clips will I need to replace the factory crimp type ones, 20mm x2 ??. I might as well replace the vac line while I'm in there too, is it 4mm?
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  9. evilscotsman
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    evilscotsman Space Cowboy

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    [Sep 24, 2010]
    as long as the clips are slightly bigger they will close down ok so not critical there, and the vac pipe may be 3mm ID, the diesel ones are all 3mm except a couple of bits but not measured the petrol ones.
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  10. voteforpedro
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    voteforpedro Member

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    [Sep 24, 2010]
    I just used a zip tie.
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  11. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator VCDS Map User

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    [Sep 24, 2010]
    4mm pipe, i doubt you will get 3mm over the NUB on the DV
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  12. evilscotsman
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    evilscotsman Space Cowboy

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    [Sep 24, 2010]
    some pipes are 4mm and some are 3mm, if he was replacing them all he would likely need both sizes i meant Mark :)
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  13. NineNails
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    NineNails Proud sponsor of the snack food industry

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    [Nov 2, 2010]
    A belated update:
    Finally got round to fitting the new valve whilst I had the turbo intake pipe off and it's totally cured the 'flutter' Top advice fella's, cheers!
    Glad I never bothered with the Forge nice shiny billet one coz I didn't realised the dv was down under the chassis leg, you'd never see it!
    Si.
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  14. evilscotsman
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    evilscotsman Space Cowboy

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    [Nov 2, 2010]
    nice one Si glad its fixed :)

    I got my legacy TT with a huge bailey piston DV on it, and its LOUD so I put a sock over it doubled back and forth, quietens it but does flutter slightly as the boost escapes slower lol

    Sounds cool tho!

    I just found out today why it only does 21mpg....its got anti-lag fitted, no wonder the VOD is non-existent in the first 3 gears and is so brief and only appears at 5k for a split second in 4th and 5th ....it injects raw fuel into the turbo hot-wheels to fire them round and keep them spinning - thats why it sounds like a demented megatron when you rev it! Backfires and pops on the over-run too, sounds fookin wicked.

    Had it at kwikcrap for its mot today, the guy went wtf is that thing plumbed into the up pipe - looks like a second lambda but its got a pipe coming from a box connected to the fuel system....turned out to be an anti-lag injector unit!
    Last edited: Nov 2, 2010
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  15. NineNails
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    [Nov 2, 2010]
    The flutter did sound a bit cool... but on balance I really don't need any headaches with this car so standard is the way to go for me. The car is fast enough for me, so I'm not arsed with any mods unless they are tried and tested, reliable improvements.
    The new dv has made quite a difference and the engine seems a lot more responsive and free revving. Think the old one's been knackered for quite a while.
    Si.
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