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  • 292/276

    Hello,

    I just thought I'd ask if anyone has tried a Schrick 292 with a
    276 on the exhaust side...Too much of a mismatch or maybe
    more midrange power? I already have a 276 with a stock exhaust
    cam and I have found a bairly used 292 for a very good price.
    Any opinions?

    Thanks in advance,
    Philip
    sigpic

  • #2
    The largest mismatch would be to use a single pattern cam set, being that the exhaust port outflows the intake by a substantial margin, which is a bit backward as far as optimum flow balance is concerned. That being said, the 292/276 set may very well prove to be a better match than the 284/276 combination.
    2003 Mitsu EVO VIII - 2.0L / 600+whp
    1988 BMW M3 turbo - Work in progress. . .
    1986 SVO Mustang - Work in progress. . .

    Comment


    • #3
      Philip and Ted you might be onto something.

      I know we usually don't see much gain when replacing the stock exhaust system, so even if we had a bigger exhaust cam there wouldn't be much.
      People see the most gains on opening up the intake side of the S14.

      Let us know how it feels. Philip are you able to compare that to a 284/276 combo from a friends car?
      Pat

      Comment


      • #4
        292/276

        Hello,

        Thanks for responding Ted B and m3pat2...
        I think it may be worth a try...I don't have access to a 284 m3pat2...
        All the other s14 owners that I know in my area are running stock cams.
        I still may be able to figure something out though, because a comparision
        between the 292/276 and 284/276 certainly would be interesting...Actually,
        with all those cams on hand I could even try the more popular 292/284...
        I would certainly be up for it...My block is going together very soon with the
        VAC CP pistons which have valve reliefs suitable, and I have swapped a cam
        or two in my day...

        Philip
        sigpic

        Comment


        • #5
          I don't think there will be a big enough difference to truely say anything either way. Unless you try the swap on the same vehicle, same day, same dyno, same conditions, and both with a correct remap. I don't think you could produce an honest test using two seperate cars.

          FWIW, there are a number of people using the same cam on both sides (Schrick 284/284 or KK290's for example). I didn't think it was advisable but a lot of people do it and are happy with the results. But I have not heard of someone trying a Schrick 292/276 set up though. It would be interesting to hear what you think about it. But when it comes to real numbers, the less scientific the method used to get them, the less credible they are.

          Jake

          Comment


          • #6
            Where did you guys get the idea the Exhaust port outflows the Inlet?

            Heres the flowbench showing the comparison of both on a Sport Evo head:

            http://www.e30m3project.com/e30m3per...-1/chart-3.htm

            Comment


            • #7
              I can explain this:

              Gustave's testing was for an Evo 3 head, and unfortunately, only involved a pressure drop of a relatively tiny 10" H2O (18.7 mm Hg) across the ports, which is too small to reveal full resolution of port flow characteristics. That is because the actual pressure drop the port sees is much more than this. Most engineers use almost 3X that pressure drop - 28" H2O (52.3 mm Hg) for standard testing, and race engine developers frequently use 60" H2O (112 mm Hg).

              Nevertheless, while all the production S14 heads have 30mm exhaust ports, the intake ports of the US S14 and non-cat S14 head are 26mm, while the intake ports of the 215hp S14, Evo 2 and Evo 3 are 28mm. The total intake port area of the head Gustave tested (Evo 3) is 16% greater than the smaller US S14 head, so that accounts for a measurable difference. The Evo 3 head also uses larger intake valves (38.5mm vs 37mm) that increase total intake valve area by 8.2%. Due to these differences, we cannot apply the intake port data for an Evo 3 head to a regular production head.

              If we look at the data posted by Metric Mechanic (at 25" H2O), we find a different picture, along with numbers that look more representative of what we use when we talk about port flow:
              MM - See Pages 6,7

              We also see that enlarging the intake ports from 26 to 29.5 with the same size valve makes almost 16% improvement in intake port flow in itself (190cfm to 215cfm @ 10mm lift). But to put this into perspective, my Mitsu EVO VIII intake ports flow around 280cfm @ 10mm lift and 25" pressure drop on the same flowbench. That is a huge difference.

              There is very little difference in the exhaust side of the head from a US 2.3 S14 to the DTM spec 2.5L engines. Almost all the difference is in the intake side. The production US spec and non-cat S14s have the smallest intake sides. These will give the highest port velocity at low speeds (which makes the engine 'feel better' in normal driving), but give the least overall flow capability.

              Soon I will have some very good before/after flow data for my S14 head in pure factory configuration vs our all-out street porting effort (max flow with least compromise to velocity). I will post it in a new discussion when it's complete.
              2003 Mitsu EVO VIII - 2.0L / 600+whp
              1988 BMW M3 turbo - Work in progress. . .
              1986 SVO Mustang - Work in progress. . .

              Comment


              • #8
                292/276 Cams

                I thought about trying something like this as well. Take a look at the 2.3L rally cams, the valve lifts are very different. I am thinking of trying the Schrick 284 on the inlet and the EVOII 264 on the exhaust.

                Comment


                • #9
                  Not to make the discussion more complicated, but intake runner length tunning can also affect the hp possible with larger cams (to take advantage of the increase in air flow).

                  Going from the stock US S14 intake horns to shorter ones made a big difference above 5,000 rpm at the expense of losing power below, due to intake pulse tunning being out of phase.

                  Hopefully with different people trying out various combinations we can find a good compromise and formulate a good general rule. For one person to undertake all combinations would take lots of time and money.
                  Pat

                  Comment


                  • #10
                    You went from the factory to which intake arrangement?
                    2003 Mitsu EVO VIII - 2.0L / 600+whp
                    1988 BMW M3 turbo - Work in progress. . .
                    1986 SVO Mustang - Work in progress. . .

                    Comment


                    • #11
                      curious to hear how you like the 292/276.. go for it..
                      Mark Williams
                      Dallas, TX

                      Nothing says "welcome to the neighborhood" like a search... oh wait... looks like they are all gone! :rastajake:

                      sigpic

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                      • #12
                        292/276

                        Hello,

                        Thanks for all the feedback...
                        I'll post back in the Spring when I've tried this combo out.

                        Philip
                        sigpic

                        Comment


                        • #13
                          Ted...I went to e34 M5 TB's including the M5 intake horns. This gave me the biggest gain above 5k, but also lost below this rpm. Judging by the power delivery (mid to top-end) I suspect a supercharger in addition to this combination would make a very potent engine.

                          I would think if one were to implement a turbo charger, you would want an engine spec that provides more torque since the turbo would make up for flow restrictions on the top end.

                          Originally posted by Ted B View Post
                          You went from the factory to which intake arrangement?
                          Pat

                          Comment


                          • #14
                            Turbocharger or superchager, both simply act as air compressors, neither actually force air into the engine because exhaust pressure rises proportionally on the back side. The M5 intake runners would react similarly in FI engines, as the turbo and SC increase air density, but not volume. Turbo and SC engines would lose torque below 5k rpm too.

                            Intake runner area and length are largely a function of engine displacement and anticipated torque peak. Whatever works for NA engines works (or doesn't work) for turbo and SC engines too.
                            2003 Mitsu EVO VIII - 2.0L / 600+whp
                            1988 BMW M3 turbo - Work in progress. . .
                            1986 SVO Mustang - Work in progress. . .

                            Comment


                            • #15
                              If I understand your comment correctly, Bernoulli's theorem still applies in FI engines. In addition you're stating the exhaust exit will still be limited in throughput for FI due to backpressure.

                              Not trying deny what you've said, just trying to explain my theory. Assuming you have increase flow capability on the exhaust side (larger valves and exhaust system).

                              My reasoning in thinking a SC would help increase low end:
                              If running larger cams lets say 292 or greater intake cam, larger TBs say 50mm and the intake runners where shortened for power above 5k.

                              Just the combination of 292s and larger TBs would reduce torque and compunded with shorter intake runners. You would loose intake velocity (venturi effect) vs. a stock intake setup and cams and exhaust.

                              Wouldn't you gain some torque back with a SC, since it would negate the loss in venturi effect at lower engines speeds due to the larger intake combination and exhaust? In addition you would still retain what you gain up on top-end with the increase in cams and intake tunning.
                              Pat

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