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blow off valve.... i know i know

Discussion in 'A3/S3/Sportback (8P Chassis)' started by z1mma, Sep 26, 2012.

  1. z1mma
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    z1mma Member

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    [Sep 26, 2012]
    :rolleyes:

    Ever since i was a kid i wanted a turbo car so it can sound like evos that i seen around in those days... Ive had my s3 for awhile now and when i bought it it was one mod that i was not gunna touch at all but as time has passed the kid inside me wants it!! Lol

    So... Where can i buy and fit and what is best for whoshing sound for my s3 :eek:


    Thx

    Z
    #1
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  3. S.
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    S. Well-Known Member

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    [Sep 26, 2012]
    after i wrote original message i saw your signature.
    doesn't your car make enough sound?
    mine did with oem dv and forge vacuum one the same.
    with spacer i wouldn't bother.
    #2
  4. mjr901
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    mjr901 S3 Pollution Plus+ Edition

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    [Sep 26, 2012]
    So you you want more turbo lag,less bhp and a stupid noise?

    Its effectively cutting your boost pipe as the air is no longer being recirc'c i.e less air = less power

    As 'S.' said, CAI will make you much happier!
    #3
  5. S.
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    S. Well-Known Member

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    [Sep 26, 2012]
    and then i saw his sig and realized that he has cai, so deleted the message.

    that should make enough noise, not?
    #4
  6. DeckedS3
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    DeckedS3 Active Member

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    [Sep 26, 2012]
    All you need is a CAI. Your car makes the noise now with the Rev D but it's muffled with the stock intake system.
    #5
  7. S3Alex
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    S3Alex Rarely neutral

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    [Sep 26, 2012]
    I just wouldn't do it.

    The S3's induction system is designed without this in mind,and all it does is to make a hissing sound and lose some performance......which is why I don't have one,and nor does anyone else I know of.

    You've put a good bit of money into raising the performance of your car.....don't waste it.
    #6
  8. OCD-A3
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    OCD-A3 Member

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    [Sep 26, 2012]
    I think the performance loss that's claimed with a BOV is being over stated. Keep in mind that the air that is recirculated has been through the turbo and is hotter than the ambient air the engine is pulling through the intake. Plus, a proper BOV is less likely to leak or fail then the stock DV.

    If it will add to the OP's enjoyment of the car, then I say go for it!

    And FWIW, I've got an atmospheric BOV on my A3 (2.0T) and haven't had any issues with it in 70k miles. I did not notice a loss in performance after installing it. Never have had a stall with it (I'm DSG though.) I still have the stock DV connected to the wire harness to keep the ECU happy, but it's blocked off from the turbo.
    #7
  9. S3Alex
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    S3Alex Rarely neutral

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    [Sep 26, 2012]
    Each to his own I suppose.

    None of the really high power cars have this sort of thing done to them,but if it's the sound of a different car you want.....
    #8
  10. mjr901
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    mjr901 S3 Pollution Plus+ Edition

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    [Sep 26, 2012]
    If i wanted a good sounding car i would have bought an R32....sod the blow off stuff, i've tried it, it really did effect performance.
    #9
  11. Sidhu88
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    Sidhu88 Active Member

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    [Sep 27, 2012]
    I was under the impression that having a BOV helps reduce lag. Freeing up the pressure in the intake system allows the turbo to spool up faster as its forcing air into an area with no pressure as opposed to one with pressure already. Its also supposed to be better for the turbo as it reduces the chance of turbo stall and excessive pressure on the turbo during sudden throttle closures. Tell me if im wrong. I doubt ud get any bhp gains, or less from using one, but it would make the engine more responsive. and personally i love the noise.
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  12. OCD-A3
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    OCD-A3 Member

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    [Sep 27, 2012]
    This would make sense on an A3, where the DV is on the turbo. Under boost, the entire system is pressurized, then when the throttle closes all of the pressurized air has to travel backward through the piping and intercooler to be relieved. If the DV couldn't vent all of the pressure quickly enough, sure it could stall the turbo, although I've never heard of that happening on this motor.

    The S3 is a different story though, as the DV is located in the throttle pipe just before the throttle body. This is more ideal, as the pressurized air does not have to travel backwards to vent. In my case, I swapped over to an S3 type throttle pipe and installed the BOV right there before the throttle body. Perhaps that's why I didn't see any noticeable performance loss that others have mentioned.

    Perhaps the K04 is flowing enough that an internal DV (like the K03 has) would be pushing the limits and that's why Audi chose a different setup for the S3. Purely speculation though.

    I seriously doubt that there is much difference in responsiveness between an electrically-actuated DV and a vacuum-actuated BOV (assuming you've got a good, short run of vacuum tube.) Same with BHP gains or losses, put them on a dyno back to back and I'd bet the difference is negligible. I mainly swapped for the sound, simpler relocation, and reliability (at the time, the piston DV wasn't out yet and people were tearing the diaphragm DV left and right.)
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  13. warren_S5
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    warren_S5 Moderator Staff Member Moderator VCDS Map User

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    [Sep 27, 2012]
    There's been much speculation as to the merits of aftermarket vs. OEM DV's, and the inclusion of the spacer.

    I've had the old style rubber diaphragm OEM valve, the new style solid OEM DV valve, a Forge FSiT valve, and the spacer (which I still have sat in a box somewhere).

    I've always been led to believe that the reason why the DV was relocated on the KO4 cars was in part down to heat management (there had been OEM DV's sticking on the K03 models where it was located on the turbo housing and subjected to high temps), hence the coldside relocation alleviated this issue. A benefit is it's easier to work on, but I've sometimes questioned whether having the DV so far from the turbo has any knock on effects as the pipework is long, has a right angle bend in its flowpath, is subject to high temperatures and can sag when hot (unless you get Forge one). I've also wondered if it contributes to the 'flutter' sound on the K04 cars, but best not to open that debate here.

    I had a very early Forge DV, and it felt to me like the DV was reacting slower than the electronic OEM unit. Just a perception, but after stage 2+ I reverted to a revision D OEM valve and never had any issues. I'm not saying there is anything wrong with the Forge valve, it's a stunning piece of engineering, I think it may just have been a spring incompatibility issue with the state of tune that I was running,

    I tried the Forge spacer as someone who owned an Ibiza Cupra bought the wrong one and gifted it to me dirt cheap. Yes it made an 'interesting' noise, but not particularly head turning. One thing I did note when I took it off was there was a film of oil misting inside the venting holes (no fault of the product, just a sign of the way the car was running), and this was despite running a catch can. I felt that it made the car feel a touch laggy, but we're talking an almost imperceptible difference.

    I got the best overall sound with a Forge DV, ITG CAI, and the full TBE as everything was breathing properly. Currently running OEM engine cover and exhaust system on the new car and it's like the car has asthma!
    #12
  14. audicruiser
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    audicruiser Audi Heaven

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    [Sep 27, 2012]

    Hmmmm.... The sound of the R32 is one of the best sounds in the world!
    #13
  15. veeeight
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    veeeight Well-Known Member

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    [Sep 28, 2012]
    There is a way to have you cake and eat it, it doesn't quite exist at the moment, but I'm sure it won't be long before something appears on the market.

    Seeing as most re-mapped cars produce an excess of boost in the compressor when the throttle plate is snapped shut that the standard S3 Diverter Valve can't cope with, the answer in the case of the S3 is to mount a hybrid dump/diverter valve that is both spring and electronically controlled, to vent the excess compressor boost, whilst still providing an adequate amount of airflow via the diverter valve back into the induction system.

    Now, you can buy a hydrid diverter/dump valve quite easily in the aftermarket world, but as far as I know, all are only spring controlled, it will just take someone to manufacture a hybrid valve that is both spring and electronically controlled and everybody can have their cake and eat it!

    The S3 uses a MAF for metering, so using a 100% dump valve will upset the mixture in those instances, one way out of this is to use a MAP metering strategy(new ECU) or to move the MAF sensor further downstream.
    #14
  16. IceHanger
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    IceHanger Active Member

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    [Sep 28, 2012]
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