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  • evo exhaust cam sprocket

    what should labor be to install and is it worth the trouble? be semi-kind!
    190 rev reject

  • #2
    No

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    • #3
      don't know what the labor is, but it's worth it if you value torque over horsepower. Also not worth it (in fact bad) if you have or are getting schrick cams.
      "It is needless to say that self-propelling vehicles, like other machines, will never do as much for one who does not understand them as for one who does."

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      • #4
        ok, but not necessary

        I've got the evo exhuast cam gear from the previous owner. It definitely moves the torque band down compared to other M3s i've driven (torque at 3500-5000 rpms now) and makes the car nicer around town. I would call it an adjustment versus an improvement. not better, just different.

        I probably wouldn't have spent the money myself to get it, because I like to have the power at higher RPMs.

        Plus, FWIW it puts you into higher classes for autocrossing because it modifies the cam timing. In BMWCCA, I'm running against modified E36 M3s and supercharged M Coupes on R-compound tires here in Washington, DC just cuz I have the cam gear. Can you say LAST PLACE?!

        Bryant

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        • #5
          This used to be a very common "upgrade" back in the day but people are realizing there is a trade off. These days cam sprockets and 2.5 conversions aren't the only way to improve torque. Going Alpha N or MAF will improve HP/Torque across the board if tuned right.

          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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          • #6
            how to article:

            http://www.mesaperformance.com/faqs/eurosprocket.html
            A friend will come bail you out of jail, but a TRUE friend will be sitting next to you in the jail cell saying, "Dude, that was focking awesome!"

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            • #7
              the 100 degree exhaust cam gear is
              *retarded* relative to the stock 106 degree peak timing.

              ADVANCE means you shift the cam valve lift
              profile vs crank degrees to the LEFT.

              RETARD means the curve is shifted to the RIGHT.

              so typically, the intake is ADVANCED.
              the exhaust is RETARDED to get more mid range torque.

              that article says its advanced, which to me is only
              possible by skipping a tooth...

              so which is it? what do people mean retard or advance?
              I use the definition from above.

              John
              with 98 degree peak timing intake cam,
              100 degree peak timing exhaust cam

              Comment


              • #8
                I'm with you, John. The event of the exhaust valves opening is retarded (delayed) in relation to the four-stroke cycle, i.e less overlap is created with the cam gear.

                BTW, I have the gear plus the 272 EvoIII cam on my Dinan engine, and I do have a lot of torque...

                Anders
                Anders

                "Objects in mirror are losing..."

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                • #9
                  the confusion comes about because most of camshaft timing literature refers to a single camshaft design such as a older US V8 engine that has both the intake and exhaust lobes on it. When you have a dual camshaft arrangement and are only moving one cam you are essentially doing the equivalent of changing the lobe separation angle between the intake and the exhaust on a single camshaft engine

                  So with a single cam engine retarding a cam means having the "all" valves open later in the engine cycle, but in a dual cam engine it is different. In this case you are referring to the timing of one cam relative to another. With this gear you are retarding the exhaust cam relative to the intake cam, which is increasing the lobe separation angle between the two cams. Retarding the exhaust cam in a DOHC engine means the exhaust valving events happen sooner in the cycle. This would be just like swapping out a cam in a SOHC engine with new cam having a wider lobe separation angle, assuming you dial the cam in with the centerline method, which phases the cam based in the intake lobe centerline. You've left the intake lobe centerline the same and just increased the separation angle between the intake and exhaust lobes.

                  essentially the retarding gear is reducing overlap by moving the exhaust valve closing away from the intake valve opening, this reduces reversion/crossflow at lower rpms, as you mention advancing the intake would also contribute to this, but then you would be changing the intake lobe centerline position as well, which further increased the lobe separation angle which gets into other issues like valve-piston clearance, etc

                  overlap is essential to high rpm breathing though, plus retarding the exhaust cam also means that in addition to it closing sooner, it's also opening sooner which at higher rpm means it's blowing off cylinder pressure,

                  the overall effect is that it moves moves both the TQ and HP peaks lower in the rpm range and also pivots their curves about their peak to favor the pre-peak rpm range, but then the TQ/HP curves drop off faster after their peak as well. Since HP is a function of TQ x RPM this also results in a loss of peak HP

                  stronger lowend, weaker topend
                  Last edited by TeamM3; 08-14-2004, 06:02 AM.
                  A friend will come bail you out of jail, but a TRUE friend will be sitting next to you in the jail cell saying, "Dude, that was focking awesome!"

                  Comment


                  • #10
                    in essence, retard/advance when talking about the intake/exhaust lobe separation angle is different than retard/advance of the intake lobe centerline phasing

                    so you have to be careful when reading general theory about cam phasing, when using the general theory for a single cam engine to transpose it correctly on a DOHC engine you have to be careful to understand what is lobe separation and what is intake lobe phasing or you'll get it all screwed up
                    Last edited by TeamM3; 08-14-2004, 06:11 AM.
                    A friend will come bail you out of jail, but a TRUE friend will be sitting next to you in the jail cell saying, "Dude, that was focking awesome!"

                    Comment


                    • #11
                      Originally posted by TeamM3
                      the intake lobe centerline position as well, which further increased the lobe separation angle
                      the lobe separation comment above is in error, it does get confusing at times :p
                      A friend will come bail you out of jail, but a TRUE friend will be sitting next to you in the jail cell saying, "Dude, that was focking awesome!"

                      Comment


                      • #12
                        Anders,

                        if you advance the exhaust cam relative to the crank
                        then the exhaust valve opens earlier and also closes earlier.
                        this increases peak timing. e.g. 110 peak timing on the
                        exhaust is more advanced than 100 degree.
                        this *decreases* overlap.


                        on the intake side, if you advance the cam relative to the
                        crank, then the intake valves open ealier and also closes
                        earlier. a 100 degree peak timing on the intake
                        is more advanced than 110 degree. this *increases*
                        overlap.

                        overlap is a combination from both the exhaust and the
                        intake.

                        if you plot the exhaust cam profile and the intake cam
                        profile vs. crank degrees, e.g. exhaust centered on
                        -106 degrees, TDC is at 0 degrees, intake is centered
                        on +106 degrees. then advance is to the left.
                        retard means shift to the right.

                        do you agree with this?


                        Mark,

                        on a DOHC setup why do we need to worry about
                        lobe seperation angle (LSA)? LSA would be simply
                        the distance (in crank degrees) between peak
                        exhaust and peak intake (the lobe centerlines
                        for each cam), right? But why should
                        that interest us? On a SOHC, where 1 cam actuates intake
                        and exhaust then LSA is a specification for the cam.
                        For DOHC, there is no longer such a specification,
                        which I assume you were also saying.

                        Also, for me advancing or retarding a cam is the same
                        process, regardless of whether it is for a DOHC or
                        SOHC. Like you said, a DOHC setup has 2 cams and
                        therefore we can adjust intake seperately from exhaust.

                        Or perhaps I misunderstood what you meant

                        PS: we also refer to peak timing (point of maximum lift).
                        this is always referenced to TDC. on intake, e.g.
                        we have 100 degrees AFTER TDC, on exhaust 100 degrees
                        BEFORE TDC. therefore opening exhaust earlier (advance)
                        increases the peak number, opening the intake earlier
                        (advance) reduces the peak number.

                        John
                        Last edited by John; 08-14-2004, 07:58 AM.

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                        • #13
                          I only mention it because that is how the camshaft conventions here in the USA are based, lobe separation angle between the intake and exhaust cams is just as important as the intake lobe centerline phasing to the crank, they both have an effect on the power band for a given set of lobe profiles, the only difference between a single cam nd dual cam engine is that the dual cam engine can adjust separation angle between the cams without replacing them, in a single cam engine it requires a new camshaft

                          in some instances you may want to maintain a specific separation angle between the cams and advance or retard them both equally. In another instance you may want to just change the lobe separation angle only, such as with the retard exhaust gear. Still in another, you may want to do change both the separation angle and the overall phasing. It just depends on what you're trying to accomplish because they all impact the breathing and powerband in different ways. So you can't just ignore the separation angle. If you want to understand the impact on performance you have to recognize what they mean relative to the conventions and the theory that exists.

                          Conventions are just that. You can just as easily make left be right and right be left, but if two people are not using the same convention then they'll be following each other's directions backwards.
                          A friend will come bail you out of jail, but a TRUE friend will be sitting next to you in the jail cell saying, "Dude, that was focking awesome!"

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                          • #14
                            John, maybe I'm totally screwed up.

                            I agree that advancing the intake or retarding the exhaust cam produces more mid-range. But in my view, the retarding cam gear shifts the exhaust graph (gray in the picure) to the left, thereby reducing overlap.




                            To help explain how I see it, I marked the picture with "Events in time". For a cam to be advanced, the event would be advanced in relation to the timeline, i.e. to the right. In my understanding of english "advancing" means "moving further along", and that graph is read left-to-right.

                            Do you see what in mean?

                            Anders
                            Last edited by Anders; 08-14-2004, 09:09 AM.
                            Anders

                            "Objects in mirror are losing..."

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                            • #15
                              as I understand it, advance/retard for lobe separation angle is the opposite of advance/retard for crank phasing. The cam gear retards the exhaust cam relative to the intake cam (wider lobe separation), but advances it relative to crank phasing (exhaust timing events occur sooner)

                              If you hold lobe separation angle constant and phase the cams together the general effect on performance is


                              Advancing the camshafts increases low speed and mid-range torque while causing high-speed power to suffer slightly.

                              Retarding the camshafts usually provides an increase in top-end power and consequently a slight loss in low-speed and mid-range torque

                              if you hold the intake lobe centerline constant and change the lobe separation angle (as the cam gear does) the general effect on performance is:




                              of course there is a limit at which this all comes into play and variations between combining the two, as well as engine/application specifics, but this is the general theory
                              Last edited by TeamM3; 08-14-2004, 09:45 AM.
                              A friend will come bail you out of jail, but a TRUE friend will be sitting next to you in the jail cell saying, "Dude, that was focking awesome!"

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