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Thread: Advice on wastegate piping

  1. #1
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    Advice on wastegate piping

    Hey everyoine, i am trying to finish up my down pipe setup so that i can start working on the rest of the exhaust (center exit coming ). I have an e30 with an m52b28 swapped into it, with a rapidspool/good n' tight manifold. I have my downpipe fabbed up, and the clearance between the downpipe, head, and body of the car is all pretty good.



    My big question is, is it ok to have the wastegate dump directly into the downpipe. The way the spacing works out, the wastegate lines up perfectly with the downpipe and has maybe an inch of piping needed between.





    Is there are reason I shouldn't do this? Are there advantages to having the wastegate piping longer?
    Last edited by SS Ball3r; 02-06-2019 at 07:24 PM.

  2. #2
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    this is just anecdotal hearsay but a straight up 90 merge is not the best for gate flow.
    it might* cause control issues by back pressure.

    my current setup is also very close to the exhaust as well so what i think* i perhaps improved
    to give it a better flow and just gave it longer runway to enter.
    So just cock it to the side and murge a small bend into the side of the pipe.

    i'm not a gas flow professor so my ideas could be totally shit.
    welds where flux core don't judge.

    no control issues btw 8psi spring. holds spring pressure or 16psi on controller.

    Tie in by jet jones, on Flickr
    Inside of tie in by jet jones, on Flickr
    Last edited by Robocop; 02-06-2019 at 08:14 PM.

  3. #3
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    Yeah main issue would be boost creep if the wastegate can't flow exhaust into the downpipe well enough.

    I also did similar to robocop though i tried to make my outlet curve and funnel air a bit more directional into the downpipe, but it looks like you dont really have much room to work with. I agree that if you try and cock it to the side and use a portion of a U bend to try and route it back into the downpipe flowing slightly downward that should be fine.

  4. #4
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    Thanks for the feedback. I was thinking that kinda like a paint gun, having the high velocity gas pass by the 90 degree T, it would create "suction", but i have never had a turbo car let alone build one.

  5. #5
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    The farther down stream the wastegate dumps into the exhaust the better and try to have it join at a shallow angle. Open dump would be best but the noise will drive you (and anyone near you) insane eventually. Here is how I did mine...


  6. #6
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    I was under the impression from some of my reading that an open dump pipe/screamer pipe would cause boost creep. I'm definitely in the learning stage being my first turbo car, lol. I don't mind running an open pipe for the wastegate being that this car is fully gutted, solid mounted, caged, etc. I do have a feeling tracks won't like me for that either. I will have to see how much space I will have if I rotate the wastegate opening towards the block and see if I can fit a 90 degree fitting in there.

  7. #7
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    People that have poorly designed exhaust manifolds with less than ideal waste gate exit angle, ie 90°, or the waste gate is not dumping from all six runners get boost creep. People with an open waste gate dump sometimes benefit from recirculating the wastegate back into the down pipe because the volume of wastegate gasses entering the exhaust reduces the overall capacity of the exhaust which causes back pressure which helps reduce boost creep. It works if your exhaust size is already marginal. It’s a bandaid for a crap manifold.

    Keeping the wastegate dump separate from the exhaust will net you the most power on a properly designed system. The noise is not tolerable IMHO. I’m willing to take a reduction in power to not attract attention and be able to pass the sound level checks at my local track.
    Last edited by chikinhed; 03-04-2019 at 12:22 AM.

  8. #8
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    Quote Originally Posted by chikinhed View Post
    People that have poorly designed exhaust manifolds with less than ideal waste gate exit angle, ie 90°, or the waste gate is not dumping from all six runners. People with an open waste gate dump sometimes benefit from recirculating the wastegate back into the down pipe because the volume of wastegate gasses entering the exhaust reduces the overall capacity of the exhaust which causes back pressure which helps reduce boost creep. It works if your exhaust size is already marginal. It’s a bandaid for a crap manifold.

    Keeping the wastegate dump separate from the exhaust will net you the most power on a properly designed system. The noise is not tolerable IMHO. I’m willing to take a reduction in power to not attract attention and be able to pass the sound level checks at my local track.

    Correct! recirc as an effort to "fix" boost creep is a band-aid fix that works as described above ***Does NOT always work though, in the case of shit WG position or small WG valves and high flow cylinder heads manifold design/WG position/opening on the collector become VERY important.

    In your case unless the head is ported and you have a big cam I don't think you will have more than 2 maybe 3psi of creep at most.

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