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KA24DE intake, ITBs or upsized TB/plenum/shortened runners

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  • KA24DE intake, ITBs or upsized TB/plenum/shortened runners

    Some background, this is for an S14 I race in DSP. The basics of the induction rules is I can run anything I want up to the head (and port up to 1" inside the head, but that's not an issue here) so new throttle bodies, individual throttle bodies, new plenums, new or shorter runners, are all on the table. The goal is more power (obviously) in an autocross environment and some weight loss. More power always helps, but I don't want to give up any (much?) low end since the car lives in second gear from 20-60-ish.

    I've been slowly building up parts for a new intake for my 240. I want to keep the MAFS for tuning simplicity. I was planning on running a bigger MAFS, TB, and associated piping, and dropping the lower runner section and plenum for a larger custom plenum. Basically like this.


    A guy local to me is selling a set of ITBs. Here they are for reference.
    https://drive.google.com/file/d/0Bya...ew?usp=sharing
    My understanding is these should give more power with the larger TB area, but lose some bottom end with the short runners. I'm not sure how much of a difference there would be and if it would be worth it.

    I'm not sure what route to take and could use some input.

  • #2
    You just want to buy the intake manifold I made for my KA? I'm switching to SR so I don't have much attachment to it any more.
    '95 240sx

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    • #3

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      • #4
        Your still N/A correct?
        I run a IC Cold Pipe as my intake and the response and power are nice.
        No crazy gains be something above the Short Ram and CAI in the traditional route.

        IMO personally running the Cold Pipe, with a Ported TB and Port OEM manifold can go a decent ways.
        I'd estimate a nice 5whp easy for those.
        I'm running a N60 w/ a JWT Velocity Stack and Filter.
        Even just from the MAF change gave me a nice top end gain.

        What do you have done so far?

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        • #5

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          • #6
            Originally posted by cdlong View Post
            Album about it
            http://imgur.com/a/AbUM7

            When it went into the car:


            Dyno thingy to show torque curve, impacted by the BCv2 cams it has.

            http://i.imgur.com/F4FVW1E.jpg?1

            Shoot me a PM if you want to work something out, it made 149hp on a mustang dyno, and the block was pretty worn out from 40-50 track weekends and 150k other miles.
            '95 240sx

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            • #7
              I should have been a little more specific and added "manifold" a few times. I'm considering the entire induction system, from the filter to the head. The filter and tubing part is easy, it's the manifold I'm most concerned with.

              What are the differences in the dyno chart? Just tuning, or is that with/without the manifold? That's roughly what I want to do, but having runners that short makes me nervous, I need to keep some low end for digging out of corners.

              Yes, still NA. I can't make any changes inside the engine or add forced induction, otherwise I'd be in the class with PJ and Mike, and I'm pretty sure having that much power would result in me killing a lot more cones and driving into a ditch.

              I currently have just an Injen intake, but I have an N60 MAF and Q45 TB sitting on a shelf in my garage.

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              • #8
                Differences on the chart were just tuning. I didn't have a baseline done w/ the stock manifold which I freely admit was pretty dumb.
                '95 240sx

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                • #9
                  I managed to get my DSP S13 motor up to 168rwhp with a stock (S14) intake manifold (and a few other things...,). I think that works out to the low 190's at the crank. I'd been studying what to do with the intake, but moved on, and it's sitting in the back yard waiting to be a parts donor for an S14 SM car I'm building. What's your current power level and expectations for improvement? I'd be glad to share my detailed build info if it helps.
                  Don Johnson (really!)
                  Just so you know.

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                  • #10
                    Originally posted by djsilver View Post
                    What's your current power level and expectations for improvement?
                    There is some. I would like more.

                    That's really all I know. I've never had the car on a dyno and haven't had it tuned. All of it is a work in progress.

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                    • #11
                      hmmmmmmmm..............I do have 2 sets of ITB's (Hybusa and GSXR I think) that we had intake manifolds made up from Xcessive we were going to mate up to the Xcessive plenum manifold.............

                      Was for a high compression N/A build we were going to do - but both sets are kind of collecting dust atm.

                      Also some forged KAE pistons to make a high comp DE, with prepped stock rods and ARP's......



                      don (runs away again)

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                      • #12
                        So this has turned into more of a for sale/WTB thread and less of a 'this runner length is ideal' and 'ITBs add such and such power' thread. Can we steer it back to the latter?

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                        • #13
                          I really think you should try a Ported Stock Manifold and TB with the Cold Pipe Intake and N60.
                          I think you'll be pleased with the gains.

                          Are S13 240/248's allowed as "back dated"?

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                          • #14
                            Just a full manifold? How should I go about porting it? I think a stock manifold with lower runners/plenum might be the best bet. Port that too maybe?

                            Only with a complete s13 engine, which is part of the long term plan. I'm casually looking for one to rebuild and swap in and get some other boxes checked at the same time, the intake being discussed, cam gears, tuning, etc.

                            The only problem with that plan is I won't know what parts made what power.

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                            • #15
                              For the TB and Port on the Manifold that can be done by Max Bore and they can/will also make you a gasket for that.

                              Runners I would use a dremel and just Gasket Match.
                              To do the actual runners I've seen ppl use a flex hone and just run it up and down the runner unless you wanna take the time to actually port it out with a bit.

                              You can even go as far as having the Manifold and Plenum flanges milled to give you very slightly shorter runners, you'll probably get nor more than 1/2" max but that's whatever's really.

                              A rebuilt 13 KA will be your biggest power gain I'm sure your aware of.
                              Last I checked your allowed .5mm OS Pistons, you can tight shim the Cams for slightly more use of the cam.
                              And of course your allowed that 1" of ports to be ported/matched.
                              You can even use Altima Chrome top rings to slightly reduce friction if you please.

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