What is SMG gearbox?

The SMG gearbox inherits all the advantages of the sequential shift gearbox design: gear changes can be made through the shift lever in the center console or the shift lever on the steering wheel. The driver does not need to depress the clutch, and can shift gears even when the accelerator is fully depressed. Unlike automatic gearboxes, SMG gearboxes do not consume energy or use torque converters.

In principle, all shift operations of the SMG gearbox are electro-hydraulic. SMG gearboxes use "shift-by-wire" technology, which is a technological achievement from the aviation field. Using this technology, gear changes can be completed in an instant, and no mechanical connection is required. Compared with the original 6-speed SMG gearbox, the SMG hydraulic unit and actuators of the new M5 are integrated into the gearbox housing. Once the gear needs to be changed, the control unit activates the corresponding solenoid valve that controls the hydraulic equipment of the entire system. Then, hydraulic oil with high pressure (up to 90 bar) quickly flows through a solenoid valve, enters the clutch master cylinder, and opens the clutch. Then use the solenoid valve in the hydraulic unit to open the four hydraulic cylinders in the actuator, and the latter completes the actual shifting process through four independent gearshift levers. When shifting down, the engine automatically disengages the clutch twice.