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M Double-clutch Transmission with Drivelogic - Always a step ahead

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M Double-clutch Transmission with Drivelogic
Always a step ahead
Perfect combination
M-specific Drivelogic
Sequential gearshift with paddles
Specifications BMW M3
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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.
This entire process takes only a few milliseconds, meaning that in the time even a skilled driver takes to press down the clutch pedal the M double-clutch transmission with Drivelogic has easily completed the entire process of shifting gears, continuing to accelerate in the next gear higher up.

Like in motorsport: dynamic torque peaks when shifting up, in-between gas when shifting down.
With the process of engaging and disengaging the gears continuing in a smooth flow, the positive engagement connecting the engine to the transmission is not interrupted, allowing the driver to set off smoothly and comfortably and, in particular, to shift up at an incomparably fast speed.
To provide an even more sporting driving impression and to further improve the car’s acceleration, the M double-clutch increases torque and pulling power to an even higher standard when shifting gears by means of the appropriately configured Drivelogic programs. In conjunction with the small increments between gears, these Drivelogic programs give the driver an even more intense feeling of acceleration, sensing each gearshift as the starting point for an even greater surge of power. The additional power generated in this way comes out clearly in the new transmission ratio feeding torque and traction to the drive wheels.
The combination of short gearshift times, small gear increments and the increase in torque gives the driver of a BMW M3 with an M double-clutch transmission a new, unprecedented experience of driving dynamics carried over directly from motorsport.
When shifting down the M double-clutch transmission works according to exactly the same principle. The only difference is that the electronic transmission control makes the process of engaging the clutch smoother and softer to prevent the rear wheels from being slowed down suddenly and with too great an effect.
Should the electronic control unit – for example when the driver is driving the car in an extremely sporting style or applying the brakes hard – recognise a very large gap in engine speed when changing gears, it will automatically adjust the transition of torque to the speed of the engine. This process of giving gas in between gears serves to further enhance the car’s driving stability and makes the entire driving experience even more intense. The drag force exerted by the engine comes out only to the extent desired by the driver, remaining within the limits already well known from cars with a manual gearbox.

Electronic transmission management recognising the driver’s particular preferences.
In choosing the gear to be prepared for operation, the electronic control unit naturally takes current driving conditions – that is the current situation on the road – into account: Focusing on the position of the gas pedal, engine speed, road speed and the driving program currently in use, the system recognises the kind of acceleration the driver wishes to enjoy or, conversely, whether he wishes to reduce his speed on the road.
Operating in such an intelligent manner, the transmission control consistently makes the necessary preparations for harmoniously continuing a manoeuvre initiated by the driver. So even with an extreme change in the style of motoring, the system changes gears appropriately, again at unparalleled speed and with unparalleled precision. Should the driver be required to suddenly stop the process of acceleration, for example, the M double-clutch transmission will promptly provide the transmission ratio required under such new conditions, operating just as quickly and efficiently as a conventional automatic trans-mission of the latest generation set to an extremely dynamic gearshift mode.
A two-mass flywheel serves as the torsion damper and the two clutches are activated via an integrated hydraulic module. Dry sump lubrication, in turn, guarantees a high standard of reliability and maintenance-free function throughout the entire running life of the car.

Special cooling to handle even the most extreme conditions.
The engineers at BMW M GmbH have adapted the M double-clutch trans-mission with Drivelogic not only to the high engine speed concept and the specific torque curve of BMW’s M engines, but also to the high thermal loads encountered in the drivetrain of such a high-performance sports car. As an example, the transmission fluid is kept within the optimum temperature range not only by integrating the transmission into the coolant cycle of the engine. Instead, an additional oil/air cooler helps to avoid excessively high temperatures inside the M double-clutch transmission even under extreme conditions, for example on the race track.
A further point is that the transmission fluid, being connected to the engine’s cooling system, reaches its normal operating temperature faster than usual, for example in particularly cold weather. This again helps to reduce frictional losses in the warm-up phase and saves fuel in the process.

Last Updated on Saturday, 22 March 2008 18:38  

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