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The M double-clutch transmission - page 5 / 21





5 / 21

BMW Media Information

1/2008 Page 5

Moving over to production cars, the problem so far was that the gearshift comfort required in everyday use could only be achieved in combination with far less powerful engines and with far less torque. But now, for the first time, the benefits of a Double Clutch Gearbox are available for the first time even under supreme loads. The M double-clutch transmission with Drivelogic is indeed the first power transmission of its kind the world over conceived and designed for engine speeds of up to 9,000 rpm.

A further advantage for the driver of a BMW M3 is the systematic control concept ensuring maximum driving dynamics also in motorsport: Gearshift paddles on the steering wheel guarantee a very fast and, at the same time, safe gearshift in all situations, the sequential shift pattern serving to minimise the risk of making a mistake when shifting gears.

Always a step ahead when shifting gears. The M double-clutch transmission with Drivelogic combines two gearbox components in one common housing with the same compact dimensions as a conventional manual gearbox. The “heart” of the new M double-clutch transmission in technical terms is formed by the two oil-cooled wet clutches. One of the two clutches is for the even (2, 4, 6), the other for the uneven (1, 3, 5, 7) gears and, in addition, for the reverse gear.

While driving, one of the two clutches is always closed, the other is open. When accelerating – and when shifting down – the clutches are activated in an alternating process, one after the other. When shifting gears, therefore, the first clutch opens just as the second clutch is closing. This ensures an absolutely smooth and comfortable and at the same time an incomparably fast gearshift without the slightest interruption in the flow of power.

This interaction of two clutches ensures an unparalleled rate of gear change in particular because the transmission control unit pre-selects the next gear with the transmission ratio matched ideally to engine and road speed and keeps this gear waiting for immediate operation. So if the BMW 3 Series is accelerating, say, in third gear, an immediate flow of power is ensured by the appropriate clutch and the gearbox component controlling the uneven gears.

While all this is happening, the gearbox segment responsible for the even gears shifts to the gear required, in this case to fourth gear. The only operation required for this purpose is to close the clutch for fourth gear, at the same time opening the clutch for third gear, the power of the engine then being transmitted through the new gear with its different ratio to the wheels.

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