2001.09.14 - ZF delivers sporty alternative to Sequential manual transmission (SMG) from ZF in new BMW 3 Series

ZF has worked with its customer, BMW, and the hydraulic specialist, Magneti Marelli to develop a transmission which combines automated shift and clutch processes with manual operating functions. This sequential manual transmission (SMG) will be available as of model year 2002 as special equipment for the BMW 3 Series. The SMG is based on one of ZF's five-speed manual transmissions and has been adapted for automated shift processes: an electro-hydraulic shift unit works with the engine electronics to undertake all shift and clutch processes which can be triggered manually by the driver.

"By developing the SMG and launching it into volume production, we have done much more than just launch a new product onto the market", explains Dr. Michael Paul, Group Executive of ZF Getriebe GmbH: "On the basis of this development, ZF can also provide all manual transmissions in automated versions and has therefore extended its product range.?

The SMG is based on tried and tested ZF technology: an electro-hydraulic shift unit has been added to the S5-31 5-speed manual transmission. This control system provided as an "add-on? system is responsible for the mechanical shift and clutch processes and co-ordinates these with the engine control unit.

ZF engineers have also made adaptations to the transmission itself without which the high level of drive comfort and sporty characteristics of the SMG transmission would not be possible: they have for example adapted the internal shift components of the S5-31 to the requirements of an automated manual transmission. The housing geometry has been modified for the attachment of the electronic control unit and an extensive range of sensors are fitted directly onto the transmission in the SMG. As a result, these measures have made extremely short shift times of several milliseconds possible.

The development work for the SMG was started in 1999 and was driven forward by the partners, BMW and ZF, as well as the hydraulic specialists, Magneti Marelli. Only two years later and the SMG was ready for volume production.

For the first time ever, drivers of mid-range BMW's can therefore opt for a sporty alternative to the "traditional" method of shifting and engaging the clutch. The driver triggers the shift process using paddles under the steering wheel or using the shift knob on the central console. Gearshifts are conducted "sequentially", i.e. one after another in upshifts or downshifts. Featuring an input torque of up to 340 Newton metres, the transmission is also suitable for more powerful engines.