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Thread: UUC Ultimate Flywheel and Clutch

  1. #1

    UUC Ultimate Flywheel and Clutch

    As most of you know by now, the clutch used in the M5 and Z8 is not known for its longevity. Part of the problem is the dreaded clutch delay valve (CDV) which causes the clutch to slip a bit during initial engagement and undoubtedly contributes to accelerated wear. The other problem may well be that the clutch itself is undersized. For mild-mannered street use, this really shouldn't be a concern but if you like to drive in a spirited fashion or take your car to the track on occasion, the standard clutch may wear out much faster than you would like. If you do a Discovery supercharger kit and get to play with over 600 lb/ft of torque then the stock clutch is woefully inadequate (read toast).

    What we really need is a clutch with more friction surface area and/or more pressure and while we're at it, let's lighten the flywheel for an increase in power delivery and faster blips during heel and toe downshifting. UUC to the rescue!

    UUC Motorwerks, the company that brought you the Ultimate Short Shift Kit (my favorite), has developed an amazing clutch and flywheel package for the Z8 which solves all of the problems mentioned above and provides the benefits of a lightened clutch/flywheel combination. This Ultimate Flywheel and Clutch package utilizes the clutch from the V-12 engined 850CSi and a custom made aluminum flywheel with a steel friction surface. The result is a 50% increase in friction surface area, a substantial increase in clutch pressure, and a 13+ lb. overall weight reduction.

    UUC is confident that clutch life will be greatly extended and they supply a new clutch slave cylinder to keep clutch pedal effort the same as stock but with better "feel" due to the increased surface friction surface area. The other benefit to this package is the reduction in weight of the rotating mass of the clutch/flywheel combination. Now, this can be a bit tricky, with the unwanted side-effect of audible gear lash not uncommon, but I'm happy to report that UUC has done it the right way. On some cars with excessive wear in the transmission gears, there may be a slight amount of gear lash noise audible at idle, but in most Z8's, there shouldn't be any audible noise associated with the new package. For complete details on this aspect of the installation, please see the technical section on UUC's website (UUCmotorwerks.com). The reason this 13+ lb. weight reduction is so important is because it provides a substantial performance increase during acceleration. At steady state RPMs, like on a dyno, the weight reduction really won't show up as an increase in measurable power, but during acceleration, that same weight reduction will effectively lighten your Z8 by an astonishing amount. The reasons for this are quite complicated, but let me just give you some examples to demonstrate my point.

    With the UUC lightened flywheel/clutch package on an M5, during acceleration in first gear, the car will perform as if it weighs 394 lbs. less than stock! If we use a typical conversion factor for translating weight savings into power increases of 10 lbs. lost = 1 HP gained, that is the equivalent of an additional 39 HP! Unfortunately, since this relative gain is directly related to the overall gear ratio of the drivetrain, the benefits are reduced as we go to higher gears. Still, the gain in second gear is 15 HP, in third gear it is 8 HP, in fourth gear it is 5 HP, in fifth gear it is 4 HP and in sixth gear it is 3 HP. So the real benefits will only be felt during acceleration in the lower gears but those benefits are substantial. And, for those of you running the Quaife LSD with 3.64 gears, the effective HP increase will be even higher in every gear! Plus, when you blip the throttle to match revs during downshifting, the engine's response will be noticeably quicker.

    UUC offers 4 different stages of clutch choices depending on how you drive your Z8. They have a Standard clutch which is perfectly adequate for unmodified cars used on the street that runs $2750 plus a $600 core charge which is returned when you send them your old flywheel. If your car has been modified to produce significantly more power but still is used mainly on the street, they offer the Power clutch which has a higher pressure and is what I have chosen at $2950 plus core. If you track your car frequently, they recommend their Stage 2 clutch which features segmented Kevlar friction pads for $2950 plus core. This will be a little bit grabby but will hold up much better under extreme conditions. Finally, for the Shadowmen of the world, they offer their Stage 3 clutch which uses a 6 puck carbon/semi-metallic friction surface design and can handle anything your S62 can dish out.

    Of course, while you're swapping the clutch and flywheel, it's the perfect time to remove that frustrating CDV.

    I am very impressed with the work UUC has done to put this package together. Frankly, this is the clutch/flywheel package BMW should have installed from the beginning. UUC clutch/flywheel and you can contact them at 908-874-9092, ask for Sunny!

    Grease Monkey
     
    Andrew Macpherson

    Expert Z8 Inspections, with full support for both Z8 sale and purchases.

  2. #2
    Team Z8 dwz8's Avatar
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    On their website, UUC states:

    From a maintenance viewpoint, the use of BMW/Sachs clutch components means that future replacement components are readily available at any BMW dealer and installation follows standard BMW guidelines.


    So is it possible to get all parts from a BMW dealer? Why then buy from UUC?

    How big is the difference between "Power Clutch" and "Stage 2"?

    I take my car to the track occasionally, but I don't want to lose the ability to drive it in normal traffic...

    Any insight is appreciated.

  3. #3

    I don't have mine installed as yet....

    but both the clutch and short shifter kit are on my shopping list, so I can only tell you what I've heard and read.

    From UUC's website: ...converts the V8 M5 / 540i / Z8 to use the 280mm (11.02") clutch components from the legendary 5.6l V12-engined 850CSi as used in the S6S 560G gearbox.

    I think what is meant here is that once the flywheel & clutch assembly is in place the expendible plates are the parts easily replaced by any dealer, but you'll have to specify that you're using 280mm (11.02") clutch from the 5.6l V12 850CSi.
    Andrew Macpherson

    Expert Z8 Inspections, with full support for both Z8 sale and purchases.

  4. #4
    Team Z8 dwz8's Avatar
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    Quote Originally Posted by macfly
    I think what is meant here is that once the flywheel & clutch assembly is in place the expendible plates are the parts easily replaced by any dealer, but you'll have to specify that you're using 280mm (11.02") clutch from the 5.6l V12 850CSi.
    Well, that should work for the standard clutch. For the power clutch and higher stages there must be different part numbers.

    Do you have any insight on how big the difference is between "Power Clutch" and "Stage 2"?

    Thanks for your comments,
    Dieter
    PS: Looking forward to see you next week in Munich.

  5. #5

    I have to confess I have no idea....

    as I haven't spoken to UUC yet about which clutch I'll need. Once I have ordered my parts I'll post some more info.

    I'm looking very forward to Muncih weekend too, I understand there may be as many as 60 Z8's attending, that's 10 times more than I've ever seen at a US gathering!
    Andrew Macpherson

    Expert Z8 Inspections, with full support for both Z8 sale and purchases.