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BOVs and getting low

Discussion in 'A4/S4 forum(B5 Chassis)' started by xcore, Oct 5, 2009.

  1. xcore
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    xcore New Member

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    [Oct 5, 2009]
    hi there im in the process of purchasing a 1.8t r plate a4, i may get flamed but i want that dumpvalve tishh, is the best way getting a split valve? do the atmospheric ones really f*ck up the engines ecu? i take it the recirc ones make no sound?

    does drilling your airbox or using an opencone filter give you any extra sound from the turbo?

    are there cheap coilovers avalible i.e. the hottuning ones etc?

    cheers lads
    Last edited by a moderator: Oct 6, 2009
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  3. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Oct 5, 2009]
    An open cone filter will give you a bit of tish even with the stock recirc valve.

    I'm not a fan of barry-valves, but if you want one, then a "splitter" will help keep the ECU a bit happier. It gets upset because your dumping air which has already passed thru the airflow meter, and therefore it fuels for it, but it never reaches the cylinders.
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  4. Geeman
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    Geeman Low Life

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    [Oct 5, 2009]
    When I have my cone filter on, I used to get a similar sound to a dump-valve operating. Maybe that's a better way to go, rather than going for a atmospheric DV.

    If you do go for a cone filter, be sure to create some kind of heat-shield to protect it from the heat of the turbo!
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  5. olds_kool
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    olds_kool Active Member VCDS Map User

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    [Oct 5, 2009]
    i run a k+n cone and forge 007 recirc. they make a nice noise and it gets louder when cars chipped
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  6. Oranoco
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    Oranoco Well-Known Member

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    [Oct 5, 2009]
    Ditto, mine is very audible now. When giving it beans it makes a chirrup sound rather than the classic DV "Tshhh" sound. If you go with the cone filter you really need to ber very carefull that the filter isn't heavily oiled as the oil comes away from the filter and fouls the MAF. I spent the first couple of months removing the cone filter and cleaning the MAF up with electrical contact cleaner. Also need to ensure it gets an adequate supply of cold air.
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  7. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Oct 5, 2009]
    Isnt "chirrup" the characteristic noise of compressor stall?
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  8. DEEJAY TQS
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    DEEJAY TQS Member

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    [Oct 5, 2009]
    some dump valves depending on which one you get make different noises

    my old collins dv on my meg use to sound good when the car was standard, soon as i got a stage 2 map it sounded awful, only way to describe it as darth vader having an asthma attack, so differnet boost levels make the dv sound different

    compressor stall is totally different, it sounds like a fluttering noise
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  9. Oranoco
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    Oranoco Well-Known Member

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    [Oct 5, 2009]
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  10. Nez
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    Nez Member

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    [Oct 5, 2009]
    This sounds like a chicken noise :hubbahubba: or some kind of birds :)
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  11. Oranoco
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    Oranoco Well-Known Member

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    [Oct 5, 2009]
    Better than a DV and not damaging to those cars. Really mis the old girl it was fantastic for upsetting the local Scooby and Civic Type R drivers with
    #10
  12. gaz71
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    gaz71 1.8T Quattro Sport AJL

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    [Oct 5, 2009]
    Right I'm totally confused now :think:

    So is this compressor stall or just the sound on DV releasing pressure through filter. ie if my TQS sounds similar should I be getting worried?
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  13. Dan Gliballs
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    Dan Gliballs Active Member

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    [Oct 5, 2009]
    My Astra GTE just used to sneeze when I changed gear.

    [​IMG]
    Last edited: Oct 5, 2009
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  14. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Oct 5, 2009]
    gaz: if your A4 is making that noise then i suggest the dump valve is broken, and your risking damaging the turbo.

    Oranoco: it could perhaps be described as a "chirrup" noise, couldnt it? :p
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  15. my96A4Turbo
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    my96A4Turbo New Member

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    [Oct 6, 2009]
    gaz, chatter/wastgate chatter/compresor stall ect ect is what you hear from rally cars,,,Rally car dont run DV so thay get turbo stall/chatter ect ect...this help keep the rally cars on boost as its nowhere to vent so it stalls the turbo(thats what the noise is),,,,good thing for rally cars as thay can replace a turbo every few races/race..but not for road going cars as it can brake turbos.....unless you get 1 strong anuff......

    i ran my subaruRA without a DV for a month or so...sounded just like a rally car...i only done this as i new the td05 turbo could take it and wantedd to see what it was like...but even that would of broke sooner or later so the DV went back on, plus it was doing my head in..


    barry valves lmao, class aragorn:laugh:
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  16. gaz71
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    gaz71 1.8T Quattro Sport AJL

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    [Oct 6, 2009]
    I meant Diverter Valve. Mine makes a more ppsssttt sound than a whistle but similar to the posted vid, hence my question
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  17. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Oct 6, 2009]
    Gaz: if its compressor stall, it will tend to go "cha cha cha cha cha..." whereas a dump valve will just make a single pssssstt noise.

    Sometimes you will find that on stock motors the dump valve wont open when just revving it at idle or whatever. I was tinkering with a mates volvo 940 turbo once, and with the airbox removed and revving it at idle, it chattered like a goodun, driving it though it dumped like normal.

    What noise are you getting? Can you describe it better? Or perhaps take a small clip of it on your phone?

    My96A4: Please dont call it "wastegate chatter" as its absolutely nothing to do with the wastegate, i've really no idea where the term came from, you could weld the wastegate shut and the noise would still occur exactly the same. It also doesnt keep the turbo on boost. Infact its the exact opposite, it stalls the turbo, hence the noise and dangers of damaging the shaft.
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  18. Oranoco
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    Oranoco Well-Known Member

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    [Oct 6, 2009]
    It's not strictly true to say the chatter damages the turbo as some turbo's are more resistant to the effects of compressor stall. Certainly the Garret turbos used on the RS Turbo's and Cosworths will cope quite fine with it. The only exception is the small turbo Escort Cossie but that is down to the MAF sensor as it can't tell which direction air is being passed over it and the fueling is upset.

    I know my Escort runs no DV and hasn't done for years despite being run at 25psi. In fact there are very few of the top cars of this type running them.

    If your Audi is making a chattering sound it would indicate the recirc valve is not opening. I'd be more worried about the upset fueling than possible turbo damage imho
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  19. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator VCDS Map User

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    [Oct 6, 2009]
    The poor K03 turbo has such a small dia shaft compared with the Garret in the cossie, thats what the chatter will damage
    #18
  20. gaz71
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    gaz71 1.8T Quattro Sport AJL

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    [Oct 6, 2009]
    This is a vid from youtube but it mimics the sound I'm trying to describe.

    http://www.youtube.com/watch?v=dYz_NzogpZM

    I noticed it while I was running a cone filter - both at idle and, as in vid, when I lifted off throttle whilst driving. I have since refitted the airbox and do not notice this sound but that could be due to the silencing qualities of the airbox.
    I have a remap and 710N Diverter Valve.
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  21. Oranoco
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    Oranoco Well-Known Member

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    [Oct 6, 2009]
    That sounds like chatter to me but I've got background noise on here. Not what you want on these cars
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  22. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Oct 6, 2009]
    it does sound like chatter, but does it do it at full boost or just at light throttle as in that video?

    It might just be the stronger spring in the 710N isnt opening with low boost, so just like that volvo i mentioned you get chatter when revving it at idle and when driving on light thottle, but give it full boost and it will dump normally.
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  23. gaz71
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    gaz71 1.8T Quattro Sport AJL

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    [Oct 6, 2009]
    Sorry, my fault, forgot to mention that the noise occurred when I was running pre-map and with standard 710 DV. It would occur at idle and when accelerating, I have a pretty heavy foot :)

    I'm now trying to figure out how the 710 works as the way it is fitted seems to suggest that vacuum from the intake manifold opens the valve, working against the spring, and positive pressure, from boost, allows to spring to close the valve.

    Am I just being a dullard or is this right?

    Totally confused now !!!!
    #22
  24. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Oct 7, 2009]
    Ok, the valve has 3 "ports". One from the pressure side of the turbo pipework (call this 'in'), one return to the turbo intake (dump), and one line to the inlet manifold (sense).

    Under normal driving conditions, both sense and in are at the same pressure, and the spring acts to keep the valve closed. When you close the throttle, there is still positive pressure at the 'in' port, but now the sense line is pulling a vacuum, this difference across the valve overpowers the spring, causes it to open, and the pressure waiting at the 'in' port is released thru the 'dump' port. The spring is now acting so that when the pressure drops the valve will close again.

    Given that in closed throttle, after-dump situations there is often much more vacuum in the inlet than is present at the DV's 'in' port, the spring needs to be strong enough to keep the valve closed even though there is a difference across the valve. It also needs to be strong enough to keep the valve shut under big boost (even though both sides of the valve should be at boost pressure, and therefore the forces on the diaphram equal, in practice you need a heavier spring to stop it leaking)

    What this means is if you only have say 2 or 3 PSI at the 'in' port, the spring is often strong enough that the valve wont open, and you'll get a bit of compressor stall. Its more likely to happen with the 710N as it has a stronger spring then the 710/710A valve. Compressor stall at 2-3psi really isnt a problem, so if thats all thats happening then i wouldnt worry about it.

    If however your getting stall when coming off the throttle at full boost, then i suggest that theres something odd going on! Possibly a blocked vacuum hose or a faulty dump valve.
    #23
  25. gaz71
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    gaz71 1.8T Quattro Sport AJL

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    [Oct 10, 2009]
    Thanks for the info regarding the Diverter Valve.

    If you don't mind me asking - where is the dump valve located? I was under the inpression that the Quattro was a recycling system and didn't have a dump valve, using the Diverter Valve to recycle the boost back into the intake.
    #24

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