Announcement

Collapse
No announcement yet.

Let's talk intake manifold design

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    Let's talk intake manifold design

    Last time we talked about cams and headwork and intermittenly touched on the intake manifold and its drawbacks.

    (If you are hear to say, stupid/don't waste the effort/you're an idiot/"You should just do a 24v swap," stop now, and don't post.)

    I'm buying matt325is intake manifold flange as a starting point for a custom intake manifold.

    Previous discussions have indicated the long runner length of the stock manifold as a one of the obstacles to high RPM flow. Basically my idea for the intake manifold is a Dbilas style setup, minus the individual throttle bodies of course.

    My two main concerns are:
    1. Size of the airbox
    2. Shape of the airbox

    1. I want to make sure the airbox is large enough and will replenish fast enough for each intake stroke of the crank. I don't know how many of you are familiar with sportbike stuff and so called "Big Bang" bikes, but for instance the new R1 uses a wildly timed crankshaft to improve smooth running etc, lots of discussion about piston speeds and throttle response and shit, but the main reason they don't just have a piston firing every 90° of crank rotation is that the airbox would not be able to refill fast enough for each intake stroke.

    2. A simple rectangle with the throttle body on the side, ie exactly like the Dbilas setup or a "house" shape with the side of the rectangle slanting outwards to long side, or even more a 666fabrication style intake (which also matches the E46 M CF airbox I think).

    What say you?
    Need parts now? Need them cheap? steve@blunttech.com
    Chief Sales Officer, Midwest Division—Blunt Tech Industries

    www.gutenparts.com
    One stop shopping for NEW, USED and EURO PARTS!


    #2
    Look at eli's ITB thread, also BrownBrick IIRC at emotech have made some good m20 manifold groundwork.

    Comment


      #3
      http://www.r3vlimited.com/board/showthread.php?t=109307


      /thread

      Comment


        #4
        Originally posted by Farbin Kaiber View Post
        Look at eli's ITB thread, also BrownBrick IIRC at emotech have made some good m20 manifold groundwork.
        TurboBrown. His project thread is amazing.
        cars beep boop

        Comment


          #5
          stupid
          don't waste the effort
          you're an idiot
          "You should just do a 24v swap,"


          hahahaaahahahaaa

          OK, If I were to make my own intake manifold, it seems to me all of the race guys use individual trumpets. www.kinsler.com used to sell trumpets, but good god, look at the fucking fuel pump on their start page!

          I wonder how hard it would be to use 6 trumpets inside of a plenum made of acrylic? The mouth of the trumpet can't be against the wall of the plenum or there will be too many reflective waves affecting the airflow.

          Anyway, I think the biggest thing to deal with would be the resonant frequencies and how to spread them out so you can have decent flow characteristics across the board, RPM wise. If you design and build for 8K RPM and the thing does not flow well below that (AKA too high of a resonant frequency) you will loose all bottom end.

          Is this thing gonna be a driver or WOT race car or what?

          Closing SOON!
          "LAST CHANCE FOR G.A.S." DEAL IS ON NOW

          Luke AT germanaudiospecialties DOT com or text 425-761-6450, or for quickest answers, call me at the shop 360-669-0398

          Thanks for 10 years of fun!

          Comment


            #6
            stupid/don't waste the effort/you're an idiot/You should just do a 24v swap :-D

            and seriously, I wouldn't touch it as the intake runner length is very finely tuned for a motor/application.. there is a ferrari video out there somewhere where they have variable intake length manifolds to provide a flat torque/hp curve
            Build Threads:
            Pamela/Bella/Betty/325ix/5-Lug Seta/S60R/Miata ITB/Miata Turbo/Miata VVT/951/325xi-6

            Comment


              #7
              Julien, I see your point, but the intake manifold was designed for a stock M20 as it came from BMW, not a bored, stroked, and cammed M20.

              Originally posted by StereoInstaller1 View Post
              Anyway, I think the biggest thing to deal with would be the resonant frequencies and how to spread them out so you can have decent flow characteristics across the board, RPM wise. If you design and build for 8K RPM and the thing does not flow well below that (AKA too high of a resonant frequency) you will loose all bottom end.

              Is this thing gonna be a driver or WOT race car or what?
              I want to build a high-comp 3.1L M20, so headwork/cam and everything geared for 4k-7k operation means I would want the intake designed with that in mind as well.

              Street, auto-x, HPDE car. I'm willing to give up low RPM power for high RPM power and throttle response.
              Need parts now? Need them cheap? steve@blunttech.com
              Chief Sales Officer, Midwest Division—Blunt Tech Industries

              www.gutenparts.com
              One stop shopping for NEW, USED and EURO PARTS!

              Comment


                #8
                PM me...

                No matter what you think...

                This is something I know something about.

                Comment


                  #9
                  Originally posted by z31maniac View Post
                  Julien, I see your point, but the intake manifold was designed for a stock M20 as it came from BMW, not a bored, stroked, and cammed M20.



                  I want to build a high-comp 3.1L M20, so headwork/cam and everything geared for 4k-7k operation means I would want the intake designed with that in mind as well.

                  Street, auto-x, HPDE car. I'm willing to give up low RPM power for high RPM power and throttle response.
                  Yeah but what I was trying to say with my post is that I don't see you building a better suited one in a shed.
                  Build Threads:
                  Pamela/Bella/Betty/325ix/5-Lug Seta/S60R/Miata ITB/Miata Turbo/Miata VVT/951/325xi-6

                  Comment


                    #10
                    ^Fair enough, but I'm still going to give it a shot.
                    Need parts now? Need them cheap? steve@blunttech.com
                    Chief Sales Officer, Midwest Division—Blunt Tech Industries

                    www.gutenparts.com
                    One stop shopping for NEW, USED and EURO PARTS!

                    Comment


                      #11
                      just pack it full of boost, all those sheetmetal intakes seem to work fine. Im a big fan of the s38 manifolds you usually see on a turbo motor.. Some how it works just fine and makes a shit ton of HP

                      Comment


                        #12
                        Originally posted by Julien View Post
                        stupid/don't waste the effort/you're an idiot/You should just do a 24v swap :-D

                        and seriously, I wouldn't touch it as the intake runner length is very finely tuned for a motor/application.. there is a ferrari video out there somewhere where they have variable intake length manifolds to provide a flat torque/hp curve

                        Variable intake

                        http://www.autozine.org/technical_sc...h_engine_2.htm

                        I was up above it, Now I'm down in it ~ Entropy - A Build thread.
                        @Zakspeed_US

                        Comment


                          #13
                          Originally posted by moatilliatta View Post
                          The truly hot setup... Not simple though... I've been toying with the idea of a staged manifold using a progressive throttle body (similar to the m42s or 4bbl vacuum secondary carb set-up) for a while now... Somebody should try it.

                          Comment


                            #14
                            it would be interesting on a straight slant six, you could use the slant of the motor of the motor for the est lengths of the runners and possible have to plenums with something connection them and throttle body. got the idea in my head, just not with words.

                            I was up above it, Now I'm down in it ~ Entropy - A Build thread.
                            @Zakspeed_US

                            Comment


                              #15
                              Originally posted by moatilliatta View Post
                              it would be interesting on a straight slant six, you could use the slant of the motor of the motor for the est lengths of the runners and possible have to plenums with something connection them and throttle body. got the idea in my head, just not with words.
                              I get it...

                              I was thinking more on the lines of a manifold within a manifold...

                              You would need an HFM type MAF setup to make it work right... The transition would play hell on a AFM...

                              I was looking for a Miller MAF a little while back just to play with this idea and even contacted Miller... But no dice... Don't even really have the time for it anyway.
                              Last edited by DCColegrove; 01-04-2009, 03:25 PM.

                              Comment

                              Working...
                              X