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  • Wastegate valve-play

    Did a RS2 boost leak test yesterday and pretty much it bled all the air directly trough the wastegate, and quite fast. Blocking the hose to the lower chamber revealed the system is airtight with no leaks. The car does reach its boost level but it isnt the quickest spooling RS2 I've driven... is this amount of play on the WG-valve a massive amount or is it still a normal bit of wear? Never checked this before but I'd say the valve guide has almost vanished?

    https://youtu.be/mSanFbeOwjM



    Thanks!

    Steve
    Last edited by Greg_S; 20th July 2019, 20:29.

  • #2
    Mine had the same problem with a lot of play in valve guide, and I´m not reaching full boost because most of it is escaping through the wastegate.

    I´m getting a used one so I can have mine repaired with a new guide!

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    • #3
      Without the ability to measure the correct clearances from an unused wastegate, its basically conjecture!
      Might be some info on this thread that could be useful:
      https://www.s2forum.com/forum/techni...e-seat-removal

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      • #4
        Found on a german forum that a new one had .19mm play...

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        • #5
          Took it apart today.

          When removing the wastegate the valve seat was lying on the manifold... that was a first! It sits loose in the bottom of the WG so that will need attention.

          Aside from that the valve shaft is worn as hell. Some places a low as 9.6mm, and it has been grinding a lot on the guide which is also heavily scored.

          Going to take it to my machineshop and have the valve refinished with a custom new guide. The valve seat will hopefully be fixeable.

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          • #6
            Got it redone with a new bronze guide and the valve cut down to 9.5mm with 0.1mm guide play. Seat also nicely lapped. He installed a thin inner bush in the guide that can easily be replaced should it ever wear again (probably not in my lifetime )

            Curious to how it will feel now!

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            • #7
              Look s like a K line insert? It will be interesting to see how well this holds up. Bit concerned over the material and the possibility that the coating from the valve will have been removed or reduced, again assuming it was hard chromed in the first place!
              Still without alternatives we need to be inventive.
              As for clearances, I have just stumbled over a Porsche 930 wastegate valve/guide clearance being 0.390/0.393 which works out at 9.91/9.99mm for new components. The Porsche valve guide appears to be nearer the material used on earlier wastegates as opposed to the cast iron on the later ones. I appreciate the components are not identical.

              Last edited by twoqu; 20th July 2019, 18:19.

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              • #8
                Can you keep this thread up to date please.? I suspect my S2 has something similar.
                85 WR Urquattro, 85 20vT International liveried RallyRep
                93 MTMS2 Avant

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                • #9
                  Originally posted by twoqu View Post
                  Look s like a K line insert? It will be interesting to see how well this holds up. Bit concerned over the material and the possibility that the coating from the valve will have been removed or reduced, again assuming it was hard chromed in the first place!
                  Still without alternatives we need to be inventive.
                  As for clearances, I have just stumbled over a Porsche 930 wastegate valve/guide clearance being 0.390/0.393 which works out at 9.91/9.99mm for new components. The Porsche valve guide appears to be nearer the material used on earlier wastegates as opposed to the cast iron on the later ones. I appreciate the components are not identical.
                  It's my GF's uncle who did it and he has 30 years experience in engine work, being mostly specialised in cylinder heads. He said it will hold better with this bronze bushing, and with 0.10mm clearance it should be near the minimum you can go since bronze expands slightly more than a normal steel bush. The valve is the bigger risk, but other option besides turning it down in size are non existent indeed. Unless someone can find out where to buy new ones coating them again (plasmacoating?) would be another option but didnt go there for now.

                  Will certainly report shortly on how it feels after some test drives.

                  Comment


                  • #10
                    Hey Top marks for getting it repaired, but kept in mind it will wear again, quickly. This might not be an issue depending on how much and the type of use the car gets

                    The wastegate valve stem needs to be extremely hard - it is about the harshest environment in an automotive application - extreme heat and no lubrication. The OE has (as Robin suggested) a hard chrome coating, once this is depleted the wear will accelerate significantly. Unfortunately simply regrinding the stem and machining a new guide will only be a temporary repair, it will wear out again quickly without a surface treatment - ideally the stem should be ground, replated (hard chrome) and then reground with an undersized guide to suit. Failing that remade out of a heat resistant alloy such as Inconel, but hard chrome is the best option for longevity. The guide would ideally be a copper based alloy to aid heat transfer.

                    EDIT: Of course this all then becomes uneconomical !
                    I think what you’ve done is the best option for a one-off just keep in mind it won’t last forever
                    Last edited by Error404; 20th July 2019, 22:01.
                    Panthero Coupé quattro 20vt
                    Indigo ABY coupé
                    Imola B6 S4 Avant

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                    • #11
                      doing something similar with mine, will report back with the results...........looks like 2019 is the year of the wastegate valve guide wear!

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                      • #12
                        Some years ago, my mecha made de same.
                        It works for some months...

                        Now I've got a ebay wastegate's low part and oem's up.
                        Bought at around of 180€ on german eBay and now is on AliExpress.
                        Maybe the AliExpress one isn't the same than XParts eBay Wastegate. Or yes...
                        How know's?
                        photobucket SUCKS
                        sigpic

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                        • #13
                          Btw pressure escaping through wastegate has almost zero effect on boost.
                          The pressure in the exhaust is always more during WOT than the boost pressure anyway.
                          And regardless we are talking about stuff that goes through the N75 bleeder opening, which is tiny.

                          However, if the play is large enough, a lot of exhaust pressure can leak through and push the WG open as it starts to act on a larger area...
                          Making clearance too tight is a really bad idea too, because it gets very hot and expands and can seize.
                          http://tuner.ee - http://www.facebook.com/tuner.ee

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                          • #14
                            On the actual reached boost indeed, but doesnt it have an effect on spool up?

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                            • #15
                              Any news in the subject? How does it works after few months?

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