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  • KA24DE Flywheel Resurfacing...

    So I decided to resurface my unknown brand chromoly flywheel myself that came as a package with a KA when I first got my car. Pulled out the clutch assembly after last race to troubleshoot terrible clutch slippage toward the end. FW runout measured at 0.008" and the friction surface itself was concave 0.002"-0.004". Needed a clean up...

    Put it on the lathe at my work using a mandrel with a large shoulder to pick up the bore and surface where it pilots onto the crank. Used a ceramic cutting tool and took very little off at a time. Ended up taking about 0.010" total off to get everywhere true. The ceramic bit did a fantastic job getting through the hotspots, BTW, with only a 0.001" difference between the worst hot spots and normal material. I then used an "Arkansas stone" by hand to bring down those "high" spots. After that, I chucked it in the lathe again and used this awesome little Brush Research Fly-Hone for rotors and flywheels in a cordless drill to get the ideal non-directional finish. Going to try it on smeared/pad deposited rotors next. You can get them at Summit or Amazon.

    Before:


    After:


    So with the amount of material I had to remove, I obviously had to machine into the outer surface of the flywheel and hence removed the step in the transition from the outer surface to the friction surface (this was practically already flush in the lowest spot prior to machining). I ended up not putting this step back in because I figured it probably isn't necessary.

    Did more thinking afterwards and am trying to find a nominal dimension for this step and can't seem to find anything. Nothing in the FSM mentions it and obviously found garbage forum threads through google with one guy claiming "they say" that the step is 0.006".....who the hell is they...

    So does anyone have any experience with this and whether it is actually necessary or not on the KA or in general? I'm thinking it probably isn't, but perhaps not having a step may affect the clamping force of the clutch due to increased spacing from the clutch disc or some other phenomena my fried brain isn't thinking of. Any and all input would be appreciated.
    Core4 Motorsports
    CLICK HERE for Wilwood FSL6R Radial Bracket & Rear Wilwood BBK GROUP BUY
    S14 VQ AER Endurance Racing Team

  • #2
    The step is important, as it provides preload to the pressure plate. Removing it essentially means you get less usable life out of your clutch disc before the clamping force drops down.

    0.006" sounds about right, as it's barely proud of the bolting surface.
    '18 Chevrolet Volt - Electric fun hatch for DD duty!


    DefSport Koni Sleeve and Spring Perch Buy!!!
    http://www.nissanroadracing.com/showthread.php?t=5902

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    • #3
      Yes, that step is important in the longevity of your clutch disc and the proper clamping load. If you're stock and using a typical marcel-style clutch disc, it's not that big of a deal.. But if you're modified and need all the grip you can or you're running a solid puck style clutch disc, then you need to have the step.

      The step should be more than 0.006". That's 0.15mm, which is the runout limit specified for the flywheel. 0.15mm is only about the thickness of a sheet of paper I'm certain that step is larger than that.
      Originally posted by SoSideways
      I don't care what color they are as long as they are LONG AND HARD.
      '04 G35 Sedan 6MT- The DD
      '96 240SX- The Track Toy

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      • #4
        Originally posted by Def View Post
        The step is important, as it provides preload to the pressure plate. Removing it essentially means you get less usable life out of your clutch disc before the clamping force drops down.

        0.006" sounds about right, as it's barely proud of the bolting surface.
        This is what I'm concerned about, but do you think 0.006" is enough to actually make a discernible difference? That's barely thicker than a sheet of paper. I feel like the steps in new flywheels are generally larger than that. Maybe more like 0.020"+
        Core4 Motorsports
        CLICK HERE for Wilwood FSL6R Radial Bracket & Rear Wilwood BBK GROUP BUY
        S14 VQ AER Endurance Racing Team

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        • #5
          Originally posted by Matt93SE View Post
          Yes, that step is important in the longevity of your clutch disc and the proper clamping load. If you're stock and using a typical marcel-style clutch disc, it's not that big of a deal.. But if you're modified and need all the grip you can or you're running a solid puck style clutch disc, then you need to have the step.

          The step should be more than 0.006". That's 0.15mm, which is the runout limit specified for the flywheel. 0.15mm is only about the thickness of a sheet of paper I'm certain that step is larger than that.
          I'll be using a new OEM replacement Exedy clutch. And, yes, I wanted to mention that 0.0059" is the runout limit specified in the FSM and probably where the 0.006" came from from "they say."

          I'm thinking it should be more on the order of 3x that for the step. Maybe I'll email Fidanza since I've had luck with them in the past...
          Core4 Motorsports
          CLICK HERE for Wilwood FSL6R Radial Bracket & Rear Wilwood BBK GROUP BUY
          S14 VQ AER Endurance Racing Team

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          • #6
            Call Exedy or ACT or Fidanza. I have used Fidanza and ACT products for quite a while and ACT's customer support has been great for issues like this.
            tell them you have one of their flywheels (that LOOKS like an ACT, but they all look pretty similar), and need to resurface it. They should be able to give you the step information from their manufacturing process..

            ..... I had an issue with ACT clutch several years ago where they changed the hub size between versions of their HD pressure plate. the sprung hub wound up interfering with the inside of the clutch plate by just a touch- less than 0.1". I called them and talked to them about my findings, and they pulled up the CAD drawings for all of the parts and told me which ones would work together between their discs and pressure plates and whatnot.. since I'd already bought a new pressure plate that didn't fit, they gave me a damn good price on a refurb unit that would fit and allowed me to return the pressure plate. in the end I 'saved' money on the deal.
            Originally posted by SoSideways
            I don't care what color they are as long as they are LONG AND HARD.
            '04 G35 Sedan 6MT- The DD
            '96 240SX- The Track Toy

            Comment


            • #7
              KA24DE Flywheel Step Height

              OK, got in touch with both Fidanza and ACT and both were very helpful.

              ACT's recommended step height: 0.005"
              Fidanza's step height: 0.006"-0.008"

              We were way off (except Master-Def, of course). I assumed based on other OEM flywheels I've seen. I asked both Techs about the condition of having the surface completely flush, both said it's not a big deal because the step is so small. The clutch will just behave just like 0.005" of friction material already wore off and reach its end of life a little sooner. Neither believed PP preload would be an issue. ACT tech guy said Nissan uses the smallest steps out of all OEM's as well. Maybe this is why the FSM makes no mention of it in the first place.

              So there you have it. I'm going to machine in a 0.008" step and call it a day.
              Core4 Motorsports
              CLICK HERE for Wilwood FSL6R Radial Bracket & Rear Wilwood BBK GROUP BUY
              S14 VQ AER Endurance Racing Team

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              • #8
                Of course I'm right.

                hah, but seriously, it's not a BIG deal, but 5 thou is about 12% your wear life assuming 1 mm on the clutch (most performance clutches rate their life at about this, most people use them longer than this, but you can see how rapidly the PP loses clamping).

                The PP spring rate is very high, so yea, 6 thou probably does make a meaningful difference in clamp load, and will give you that much life on the back side.
                '18 Chevrolet Volt - Electric fun hatch for DD duty!


                DefSport Koni Sleeve and Spring Perch Buy!!!
                http://www.nissanroadracing.com/showthread.php?t=5902

                Comment


                • #9
                  Originally posted by Def View Post
                  Of course I'm right.

                  hah, but seriously, it's not a BIG deal, but 5 thou is about 12% your wear life assuming 1 mm on the clutch (most performance clutches rate their life at about this, most people use them longer than this, but you can see how rapidly the PP loses clamping).

                  The PP spring rate is very high, so yea, 6 thou probably does make a meaningful difference in clamp load, and will give you that much life on the back side.
                  I'm curious as to what the spring rates are of a pressure plate. Maybe I'll measure the OEM one I have and we'll see if it is a meaningful difference or not.

                  0.008" Step machined in the meantime. Only 0.001" runout on this beauty now. It has never been truer...
                  Core4 Motorsports
                  CLICK HERE for Wilwood FSL6R Radial Bracket & Rear Wilwood BBK GROUP BUY
                  S14 VQ AER Endurance Racing Team

                  Comment


                  • #10
                    Lookin' good!
                    '18 Chevrolet Volt - Electric fun hatch for DD duty!


                    DefSport Koni Sleeve and Spring Perch Buy!!!
                    http://www.nissanroadracing.com/showthread.php?t=5902

                    Comment


                    • #11
                      Originally posted by gills View Post
                      OK, got in touch with both Fidanza and ACT and both were very helpful.

                      ACT's recommended step height: 0.005"
                      Fidanza's step height: 0.006"-0.008"

                      We were way off (except Master-Def, of course). I assumed based on other OEM flywheels I've seen. I asked both Techs about the condition of having the surface completely flush, both said it's not a big deal because the step is so small. The clutch will just behave just like 0.005" of friction material already wore off and reach its end of life a little sooner. Neither believed PP preload would be an issue. ACT tech guy said Nissan uses the smallest steps out of all OEM's as well. Maybe this is why the FSM makes no mention of it in the first place.

                      So there you have it. I'm going to machine in a 0.008" step and call it a day.
                      Maybe it's the pile of Mazda stuff I've been looking at recently that makes me think it should be more...
                      Originally posted by SoSideways
                      I don't care what color they are as long as they are LONG AND HARD.
                      '04 G35 Sedan 6MT- The DD
                      '96 240SX- The Track Toy

                      Comment

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