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Custom Plenum (Velo-stacks, TB size, short runners)

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  • Custom Plenum (Velo-stacks, TB size, short runners)

    So my engine builder just finished porting my SR20DET head, and offered to build me a custom intake. His plan is to modify (shorten) the OEM runners and install velocity stacks inside a custom aluminum plenum.







    I don't know too much about manifold design, but I gave him the go-signal to try it out. I've tried researching theories and concepts, but I dont think I have enough time to grasp enough to know what I'm getting into, haha! I was hoping someone could give me a crash course in this topic, or at least answer some questions I've been trying to find answers to!

    1) I was told that I may see better response all throughout the rev range with the velocity stacks?

    2) While Im already there getting a custom plenum made, should I get a bigger throttle body? I already have the S13 TB which is slightly bigger than the S14/15 versions, its 60mm compared to the later models which are 50mm.

    3) Should I expect less response, but more top end from this custom plenum? This plenum isn't HUGE, but still much bigger than OEM.

    The focus of this engine build was a reliable, responsive ~350whp for the street, canyon driving, and monthly time attack meets. So I wanted to make sure it had a fat mid range without completely sacrificing the top end pull.

    S13 SR20DET
    Poncams
    CP piston/ Manley rods
    GTX2867r .63

    So it's not necessarily focused on all out top end power. I want to retire my S13 from serious drift competition and just try to enjoy it as much as I can on the streets and local events!

  • #2
    I would keep stock runner lengths if you want midrange power.
    '18 Chevrolet Volt - Electric fun hatch for DD duty!


    DefSport Koni Sleeve and Spring Perch Buy!!!
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    • #3
      Originally posted by Def View Post
      I would keep stock runner lengths if you want midrange power.
      Agreed.

      To Marphie; If you shorten by the runner length and make up some of it with the stacks, you don't lose much if delta in runner length is minimal. However, you also do not want to lose plenum volume.
      Yes, your response should increase with the V-stacks
      Last edited by RalliartRsX; 03-13-2017, 08:25 AM.

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      • #4
        Those parts pictured are all from http://www.rossmachineracing.com/
        Velocity stacks help fill the runners from the plenum & decrease turbulent flow, increasing laminar flow. Raised bellmouths with a slight taper in the runners are a little better for performance overall. I agree with keeping the longer/stock runner lengths for your power/response goals. I have made & modified a few intakes with what I'm describing before.

        Links from Photobucket as IMG files:





        Links From Google Photos:
        https://drive.google.com/file/d/0B9N...tOUll0eEU/view
        https://drive.google.com/file/d/0B9N...xXV01lZ1k/view
        https://drive.google.com/file/d/0B9N...VwT1N1ODg/view



        Last edited by induetime; 03-27-2017, 11:53 AM. Reason: picture links try again with photobucket.
        First 300ZX to break 500whp on the Stock Turbo/Stock Long Block, boost only, no meth.
        Currently building sub-2800# 300zx Twin BW 6258 EFR, AMB Aero, TA-U & Road Race Car.

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        • #5
          Originally posted by induetime View Post
          Those parts pictured are all from http://www.rossmachineracing.com/
          Velocity stacks help fill the runners from the plenum & decrease turbulent flow, increasing laminar flow. Raised bellmouths with a slight taper in the runners are a little better for performance overall. I agree with keeping the longer/stock runner lengths for your power/response goals. I have made & modified a few intakes with what I'm describing before.
          https://drive.google.com/file/d/0B9N...tOUll0eEU/view
          https://drive.google.com/file/d/0B9N...xXV01lZ1k/view
          https://drive.google.com/file/d/0B9N...VwT1N1ODg/view



          [IMG]https://drive.google.com/file/d/0B9NjtCh4nGkGT0FEb3VwT1N1ODg/view[
          /IMG]


          Would it be possible for you to send me the pictures? I cant seem to access them haha!

          Sorry if this is another stupid question: So my best bet would be to have him fabricate a manifold with OEM runner length + stack? What about plenum sizing?

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          • #6
            Honestly, if you want low to midrange torque, you're not going to get much better than the OEM one. That's what it's optimized for. There isn't a ton of area for more plenum volume there.

            The oem plenums alll have the equivalent of velocity stacks to the entrance of runners.
            '18 Chevrolet Volt - Electric fun hatch for DD duty!


            DefSport Koni Sleeve and Spring Perch Buy!!!
            http://www.nissanroadracing.com/showthread.php?t=5902

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