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  • CF Boxes - so confused

    What then is the difference between Maxx's 15mm runner, 18mm runner and 18mm TYPE 2 boxes?
    Which is best for a mildly cammed 2.3?

    Any ideas?


    thanks!

    Kasra
    "You must drive this car before you die, it really is that good." BMWCar Magazine re:the e30m3; Oct. 2002

  • #2
    not one? damnit!
    "You must drive this car before you die, it really is that good." BMWCar Magazine re:the e30m3; Oct. 2002

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    • #3
      i belive the longer runners create more power, just like how taller velocity stacks create more turbulence and better mixture through there. im not 100% sure. but thats my take on it. the type 1 and 2 boxes the diffrence is the indentation i believe.


      edit: BTW, what do you mean by mild? our cars come mild factory. pretty much anything after market is going to be hot to extreme.
      Last edited by mrsha007; 11-04-2003, 02:17 PM.
      "Just road, seat, ASS; THE END!" - Jeremy Clarkson
      "If you had a choice between a million dollars and world peace, what would you get for your E30 M3?" - ItsNotTheNissan
      onfirelabs.com twitter.com/suga_shane

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      • #4
        evo 2 intake cam and evo 3 exhaust cam gear
        "You must drive this car before you die, it really is that good." BMWCar Magazine re:the e30m3; Oct. 2002

        Comment


        • #5
          Originally posted by Emdrie
          evo 2 intake cam and evo 3 exhaust cam gear
          oh, hehehe, then it is mild. hummm. im not sure, i dont think the 18mm would hurt. you jsut dont want to go to big, getting air into the head is harder then getting it out.
          "Just road, seat, ASS; THE END!" - Jeremy Clarkson
          "If you had a choice between a million dollars and world peace, what would you get for your E30 M3?" - ItsNotTheNissan
          onfirelabs.com twitter.com/suga_shane

          Comment


          • #6
            I believe it's the opposite. Shorter or bigger runners help top end HP while longer or smaller runners tend to help low end. Kaz, i think it's wise to go with the 48mm version incase you plan on upgrading to 48mm tbs later. The 46mm box limits you to just that. As for runner length, you really can't go wrong with 15 or 18cm versions. I believe the Type 2 box they are referring to is reshaped so that it fits over/around the stock brake fluid reservior so there is no need to relocate. Not sure how much it effects performance though.

            Originally posted by mrsha007
            i belive the longer runners create more power, just like how taller velocity stacks create more turbulence and better mixture through there. im not 100% sure. but thats my take on it. the type 1 and 2 boxes the diffrence is the indentation i believe.


            edit: BTW, what do you mean by mild? our cars come mild factory. pretty much anything after market is going to be hot to extreme.

            88 M3 - LACHSSILBER/M TECH
            89 M3 - ALPINEWEISS II/SCHWARZ
            85 323I S52 - ALPINEWEISS/SCHWARZ
            91 M TECHNIC TURBO - MACAOBLAU/M TECH


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            • #7
              im not sure about the hieght thing. i know that bigger is bettre to a certain point. to big and you lose vacume. But are you sure taller isnt better? after all, look at carbed cars, they use plates to increase distance between the carb and motor to create a beetter swirl and mixture of air and fuel. thats what i think, but dont take my word on it. i just drive this POS.
              "Just road, seat, ASS; THE END!" - Jeremy Clarkson
              "If you had a choice between a million dollars and world peace, what would you get for your E30 M3?" - ItsNotTheNissan
              onfirelabs.com twitter.com/suga_shane

              Comment


              • #8
                A longer runner is going to increase velocity to a certain point. A real short runner will wail up top but the velocity losses will affect torque. The trick is finding a compromise.. but that compromise is dictated by how hot you want the powerband to be.

                A 2.3 with E2 cams is basically as mild as it gets.. i wouldn't imagine that a CF airbox would be designed for factory long-block useage anyway. I'd go with the mildest CF airbox available unless you have plans for more work in the future.
                Alex McHenry

                Comment


                • #9
                  cool, so we were both right, to a point.

                  thanks alex.
                  "Just road, seat, ASS; THE END!" - Jeremy Clarkson
                  "If you had a choice between a million dollars and world peace, what would you get for your E30 M3?" - ItsNotTheNissan
                  onfirelabs.com twitter.com/suga_shane

                  Comment


                  • #10
                    The whole point of a velocity stack is to create a resonance with the intake charge. This resonance only occurs at a specific engine speed. This resonance "forces" more air into the cylinder at that specific engine speed. Of course, a shorter runner will have this resonance at a higher speed than a runner of a longer length(because the shorter runner has a higher resonance frequency, kind of like a shorter pipe in a pipe organ makes a higher pitch). Anyways, for a mildly cammed 2.3 I would probably go with the longer runner lengths since you are probably less likely to need the top end power. That's why on many race cars you see velocity stacks that are just a few centimeters long. They want this resonance at very high engine speeds because that is where they do all of their driving on the track. You can tune exhausts the same way. It's kind of interesting, you can actually get over 100% volumetric efficiency of the engine by tuning like this.
                    Boxy is foxy

                    1988 BMW E30 M3 2.5L
                    1985 Renault R5 Turbo 2

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                    • #11
                      the type II airbox is not just the indented vesion, it can
                      be had with or without identation. it is otherwise very close
                      to the type I 18 cm runner airbox, except the flange on the
                      type II is better.

                      the indentation is there merely for the brake fluid resevoir.
                      on a mild engine this will not pose a big problem.
                      most of the airflow is along the walls of the runners, IOW,
                      you can block off the center of each runner and still get
                      very good airflow. thats simple physics. the indentation
                      sits some distance below the runners which isolates it
                      from disturbance.

                      on wild engines (e.g. race engines with 300-320+ hp),
                      it would probably be
                      better to run without an indentation. people who build a
                      race engine also have no problem relocating a brake fluid
                      resevoir or they have dual masters anyway. the reason I would
                      not run the indentation would be to attempt to keep airflow
                      into all cylinders consistent as possible.
                      The #4 cylinder is problematic anyway, as it is sectioned
                      off by the rear wall. The vicinity of the rear wall or an
                      indentation may cause a slight disturbance in flow. To create
                      such a disturbance assumes a very high flow rate achieved
                      by high reving race engines. At lower flow rates,
                      the location of the wall/ident is far away. I would not get
                      too worried about this unless you have a very highly tuned
                      engine.

                      anyway, the customer can order the type II airbox in any
                      configuration they want.

                      John

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