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    Turbo Question for the gurus...

    Is a blow off valve activated by vacuum, or actual positive pressure against the spring? OR both?

    #2
    When your TB closes, there is vaccume generated by the engine in the manifold. That vaccume opens the bov, and I would think that the pressure built up in the IC pipes would push open the BOV. Makes sence to me.
    BP-05 Turbo-Sold
    2004 MK4 AWP Jetta GLI

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      #3
      yea, cause i know blow off valves are vacuum actuated... but then it got me thinking on whether or not the actual boost pressures help in pushing the spring open also?

      possibly a combination of both...

      however, that leads to my next question

      does the BOV remain open all the time at engine vacuum? (idle)

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        #4
        I think i got it!

        it has to be only vacuum controlled, because if it was controlled by IC pipe pressure, you would never reach full boost, because the BOV would leak it out.... right?

        anyone..

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          #5
          You need to rember that the TB has alot to do with the whole functionalitly of the BOV. When you are giving it throttle, there is pressure being exerted on every part inside of the pipes, intake and engine. That keeps the BOV closed, as does the tension of the spring inside of the BOV. When the TB closes, you have alot of air stuck with nowhere to go in the charge pipes. Now the pressure in the intake manifold has dropped suddenly. This pressure sucks the air in from the BOV signal line, opening the valve, more or less letting the spring do the work, but the air that is being sucked in by the engine lets it do this. I hope that helps you guys out.
          BP-05 Turbo-Sold
          2004 MK4 AWP Jetta GLI

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            #6
            gotcha

            so now my next question...
            if you're at idle...there is vacuum present in the intake manifold

            is this vacuum making the BOV staying open at idle?

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              #7
              _________________________________
              '12 Focus SE hatch
              '04 Eddie Bauer V8 4X4 Explorer
              '05 Saab 9-3 turbo (sold)
              '90 Mazda 323 GT (sold)
              '04 Mazda Tribute (sold)
              '92 Mazda Protege LX (sold)
              '91 Mazda Protege LX (blown engine)
              '91 Honda Prelude (totalled)
              '91 Honda CRX SI (sold)

              Comment


                #8
                good link. should probably post that in Bruce's good turbo info from the Vortex forum and make it a sticky in the FI section.
                The T3 BP MX-3 conversion has begun, and is taking forever & will kill me.

                Comment


                  #9
                  It shouldnt because it would let in un-metered air throwing off the ECU. Most people say to adjust your BOV so it is just closed at idle.
                  BP-05 Turbo-Sold
                  2004 MK4 AWP Jetta GLI

                  Comment


                    #10
                    the only thing i dont understand in that entire link, is the "quick release valve"

                    i dont understand what it is, or what it does.... and there is no pic of it

                    can anyone clear that up for me please?

                    Comment


                      #11
                      Originally posted by elscotto80
                      It shouldnt because it would let in un-metered air throwing off the ECU. Most people say to adjust your BOV so it is just closed at idle.
                      ok, so the only time a BOV would be open during idle is if it is adjusted TOO soft

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                        #12
                        Pretty much yes. I had to cut some off my spring to get it to work correctly.
                        BP-05 Turbo-Sold
                        2004 MK4 AWP Jetta GLI

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                          #13
                          I have heard that the 1st gen DSM leaks a little bit of boost, because it is made as a By-Pass valve, and just gets ran back into the intake anyways, does wnyone know if this is true or not?


                          Comment


                            #14
                            If it runs back into the inatake then it is a recirculating BOV. This can be sloved very easily, take out the duct work that circulates it back to the intake pipes. Most factory cars come with a recircualting BOV, I am running an open atmosphere one.
                            BP-05 Turbo-Sold
                            2004 MK4 AWP Jetta GLI

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