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Thread: Bottom mount down pipes

  1. #1
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    Bottom mount down pipes

    If you have pictures of your bottom mount down pipe would you post them here? Iím curious how others dealt with wastegate placement, size of exhaust, flex pipe for exhaust, and clearance.



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  2. #2
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    What manifold?

  3. #3
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    Quote Originally Posted by pbonsalb View Post
    What manifold?
    I happen to be working with a spa.


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  4. #4
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    95 M3 Turbo, 08 535xiT
    I skipped the flex pipe in my build. I went 3" TB. I have seen a few different options for wastegate placement, I am going to recirculate my wg this coming season but this is what I came up with for the time being. The DP is the easier part, the wastegate piping was a PITA. There really is not much space between manifold and frame rail. You may have better luck just buying the SPA wastegate pipe and then modifying it towards the WG side of it. The photo of the WG pipe was my first attempt, it needed to be even steeper of an angle coming off the flange at the manifold. I also had to add to the WG side of it as that picture had it interfere with the chassis brace that is under the car. I have also seen where people have the DP come closer to the frame rail and then have the WG piping come under and the WG mounts closer to the transmission. A million ways to skin a cat.

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  5. #5
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    1996 m3

    Bottom mount down pipes

    Finally got it tacked together. I pushed the downpipe towards the tranny so Iíll have room to recirc the wastegate. Itís 3Ē to a 3.5Ē just before the tranny brace. As a note for others the tial wastegate opening is larger diameter than the spa dump tube. I will be remaking that but using the flange. Bank1 o2 will be In the 3Ē section and wide and is in the 3.5Ē


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    Last edited by lisnowboarder; 12-29-2018 at 11:22 PM.

  6. #6
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    93 325is
    what turbo are you running?

  7. #7
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    Quote Originally Posted by abq View Post
    what turbo are you running?
    T3 gtx3582R


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  8. #8
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    Looks good. I ran a T4 0.82 GT35R on a boostlogic manifold on an S52 for a few years and really liked it. Did a little over 609 rwhp on a Dynojet in SAE at about 20#. Somewhere I read that a 3.5” downpipe adds power on a 3L turbo I6 at power levels above 500 rwhp. I ran a 3.5” DP.

  9. #9
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    Got the wastegate installed and itís off to a better welder than me. Someday Iíll redo the downpipe to 3.5Ē Iím not sure it would have been any more difficult. The spa wastegate location is close to the footwell so Iíll put some sort of heat shielding. Although the existing factory shields covers it all pretty well.


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  10. #10
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    Atlanta, GA
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  11. #11
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    Looks very nice.

  12. #12
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    I like that angle more. That does force the wastegate to be close to the turbo. Is there any trade offs for location distance from turbo heat?

    Anyone using push connect for vac lines?


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  13. #13
    Join Date
    Jul 2007
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    Atlanta, GA
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    E36

  14. #14
    Join Date
    Sep 2008
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    selah WA
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    1996 m3

    Bottom mount down pipes

    Wrapped and tightened which means Iím getting close to starting this thing. Used gold tape stuff on hot side intercooler pipe, titanium wrap on exhaust down pipe and waste gate, 1/4Ē push connect fittings for vac lines. I also cut part of the tranny tunnel insulation near the downpipe and replaced with the dei high temp mat foil stuff. Not sure how hot that area will be an it cleaned things up.
    I was unaware tell install that 90 degree fittings cannot be installed in a parallel orientation to the turbine shaft for coolant lines. Luckily I had left my braided lines long and could adjust the angle. Itís a royal pain to get all the flange bolts and fittings on a bottom mount. I hope it doesnít end up needing maintenance very often.



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    Last edited by lisnowboarder; Yesterday at 01:34 AM.

  15. #15
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    Looks good. Neatly and nicely done.

  16. #16
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    Quote Originally Posted by pbonsalb View Post
    Looks good. Neatly and nicely done.
    Thanks. Im hoping it will hold together for some road trips this summer.


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  17. #17
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    Jan 2017
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    RI
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    1994 325is
    Looks really good. Inspiring me to clean mine up a little.

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