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Thread: BMW's Dual-Clutch Transmission - DCT

  1. #1
    Administrator thegunguy's Avatar
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    Thumbs up BMW's Dual-Clutch Transmission - DCT

    Looks like all the speculation that BMW was moving on from SMG to a dual-clutch approach, like that Audi has been using for a few years, has come true.

    http://www.autocar.co.uk/News/NewsAr...Series/225812/

    A good explanation of how the general design works can be found HERE.

    Basically, the system has two concentric clutches and related shafts. Gears are then place in alternating order on the shafts (S1 - 1, 3, 5; S2 - 2, 4, 6). So, when a shift from one gear to another occurs one clutch/shaft is being disengaged while the other is being engaged (assume a single step change). This transition is almost seamless with no interruption in power. So, it's much faster/smoother than BMW's current SMG.

    However, I believe engaging first gear is done in a similar fashion to SMG (actuated clutch). So, low speed (parking) maneuvers could still be a little "herky-jerky" as the clutch is electronically "feathered".

    As noted in the initial announcement, the gearbox is being planned for the M3, and is scheduled to show up in spring 2008. I can only speculate, but I'm guessing this transmission will also replace SMG in the M5/6, if not in the current model, certainly in the next refresh. It will likely be available on the Z? successor to the Z8 (can there really be a "successor").
    thegunguy

  2. #2
    They did tell us that in Munich too when we we were being shown the white M3, but not sure if you were standing with me at the moment. I look forward to seeing how it works since it seems likely it'll be the only system offered on the Z9.
    Andrew Macpherson

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

  3. #3
    Administrator thegunguy's Avatar
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    Yes, I was there when we were talking about that, while bench-pressing the M6 carbon-fiber bumper support.

    The 8 speed auto sounds interesting too. Seems like 100ms is faster than SMG II. Is that right?
    thegunguy

  4. #4
    I didn't pay that much attention! I just remember him saying that SMG is no more - and with Bangle promoted out of harms way I'd say things are starting to look up at BMW. As I mentioned there I think the new M3 is styled into an odd place somewhere between bland and dull.
    Andrew Macpherson

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

  5. #5
    Sport Button On - DSC Off FWK-Z8's Avatar
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    Real cars still have three pedals

  6. #6
    Team Z8 RRZ8's Avatar
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    Quote Originally Posted by FWK-Z8 View Post
    Real cars still have three pedals

    Absolutely. I drove the SMG M3 (Hockenheim M3 training, Germany) and I thought it was horrible. With the new system coming up I still do not believe that I would choose the sequential gearbox or, as they say; the manual gearbox that is shifted sequentially.

  7. #7
    Sport Button On - DSC Off FWK-Z8's Avatar
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    18 cars, 54 pedals so far. I have never bought a car that didn't have a manual gearbox. For me, a large part of the joy of driving is the artistry of working the gearbox.

    I learned to drive on a 1970 Beetle. It was a good car for breaking bad habits very quickly. With its puny (30mm) single barrel carb, it would stall if you looked at it wrong. With 54 hp you learned to conserve speed and why they're called acceleration lanes. AND you learned NEVER to tromp on the brakes if you overcooked a corner.

    After 33 years, I though I knew everything there was to know about gearboxes, then I bought the TF - with its non-synchro first and barely synchronized 2nd, 3rd, and 4th, it was like learning how to drive all over again!

  8. #8
    Z8Mania
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    Quote Originally Posted by FWK-Z8 View Post
    Real cars still have three pedals
    +1
    and +1
    and did I mention? +1 ?