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Blow off valve or Dump valve ?

Discussion in 'A4/S4 forum(B5 Chassis)' started by K212, Jul 17, 2003.

  1. K212
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    K212 Member

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    2 Questions:

    1. Whats the diff between a blow off valve and dump valve?

    2. Would it help or hinder performance for a 1.8TQ ?

    (new to the audi turbo scene)

    thanks for replies /ubbthreads/images/graemlins/beerchug.gif
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  2. Gambba
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    Gambba Active Member

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    Well the difference between a Blow off valve and dump valve is absolutely nothing......Both of these valves are the same, just with different names, both vent the excess turbo pressure to atmosphere, and when doing so gives a Whoosh sound.

    Now, when we refer to a DV on the VAG turbo engines we are referring to a Diverter Valve, which is similar in function to the two you mention, in that it gets rid of excess turbo pressure, but it does it in a more effective way. With the DV instead of venting this excess pressure to atmosphere it puts the boosted air back into the inlet side of the system, this boosted air then helps to maintain turbo speeds during gear changes etc.

    So you can see by recirculation the excess turbo pressure not only do you ensure that the turbo remains at a higher speed, but also make the engine more economical.

    That is a really basic description of the DV used on VAG engines, but don't hesitate to ask if you want further info.

    Just another point, although dump valves can be fitted to the 1.8T it is not advisable, why? Because the system expects to see this air re-circulated back through the system, which it will not do with a dump valve, and thus performance will suffer.

    And welcome to the boards.

    Gambba /ubbthreads/images/graemlins/beerchug.gif
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  3. Ram
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    Ram Member

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    [ QUOTE ]
    Gambba said:
    Well the difference between a Blow off valve and dump valve is absolutely nothing......Both of these valves are the same, just with different names, both vent the excess turbo pressure to atmosphere, and when doing so gives a Whoosh sound.

    [/ QUOTE ]

    Gambba,

    There are two types of dump valve - recirculatory and vent to atmosphere, both are different to a BOV (Blow off valve).

    VAG Cars shouldn't use Blow off valves / Vent to atmosphere dump valves as the ECU throws DTCs as it looses air it has already measured.

    Best wishes,

    Ram
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  4. K212
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    K212 Member

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    Wow ! thanks guys for being really helpful /ubbthreads/images/graemlins/smile.gif
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