Twin-Clutch Gearbox: Notes

In BMW vehicles with powerful motorization, a twin-clutch gearbox may be in use. The twin-clutch gearbox has seven gears and it enables gearshifts without tractive power interruptions.

On the twin-clutch gearbox, the clutch control and gear changes are automated. An electrohydraulic control system handles clutch operation and gearshifts. The clutch pedal is no longer required.

The twin-clutch gearbox combines two sub-gearboxes with two clutches (designed as oil-bath clutches). One sub-gearbox with clutch is responsible for the even-numbered transmission stages (2, 4, 6). The other sub-gearbox with clutch is responsible for the odd-numbered transmission stages (1, 3, 5, 7) as well as for reverse gear.

While driving, one of the two clutches is closed. With each gear change, one clutch opens parallel to the other clutch closing. This achieves jolt-free and rapid gear changes without tractive power interruptions.

The use of two clutches enables a very rapid gear change without tractive power interruptions. Reason: Because the electronic transmission control preselects and prepares the next gear with the ideal ratio for the current engine speed and vehicle speed. Example: The vehicle is accelerating in 3rd gear. In the sub-gearbox with the even-numbered transmission stages, the gear required to continue the acceleration, in this case 4th gear, is already engaged. If the clutch responsible for 4th gear now closes, the clutch for the 3rd gear opens simultaneously. This gear shift operation takes only a few milliseconds.

The twin-clutch gearbox can be used manually in the "S" sequential mode and in the "D" automated drive mode. The gear selector switch is a bus user. The shift pulses are transferred electrically to the DKG control unit. With this gearshift method ("shift-by-wire") there is no mechanical connection between the gearshift lever or shift paddles and the transmission.

"Drivelogic" (motorsport engineering) provides a total of 11 driving programs. These are used to adapt the shift characteristics of the twin-clutch gearbox to the desired driving style.

The twin-clutch gearbox is configured for a torque of up to 520 Newton meters and engine speeds of up to 9000 rpm.

The twin-clutch gearbox weighs 89 kg (including dual-mass flywheel).