The new BMW Sequential M Gearbox
Changing gears in F1 racing cars is no longer done by means of a shift lever but, instantaneously by operating rocker switches on the steering wheel. Whereas the driver of an ordinary roadgoing car moves his shift lever in a classic H-type shift pattern to select the desired gear, drivers like Ralf Schumacher and his Formula 1 rivals just briefly pull two butterfly-type rocker switches behind the steering wheel – the “paddles” as they are referred to – pulling the right rocker switch to shift up; pulling the left one to downshift.
And while the shifting is being executed, the driver can keep his accelerator pedal floored rather the lifting off. The most advanced engine electronics interrupt the engine’s powerflow for just milliseconds allowing the control unit to effects the gear change electro-hydraulically and opens and closes the clutch. There is no clutch pedal to operate at all.
The preliminary stage of this sophisticated system, which has long become a standard feature in Formula 1, was used by BMW in its successful race-tuned touring cars as long as about a decade ago. With this system, albeit with a central shifter, gear changes are carried out in a rank, i.e. sequentially, as in the case of a motorcycle: for upshifting, the driver – without operating a clutch – just pulls the shift lever backwards, forward for downshifting. This system provides extremely short gear shift times on the one hand, and prevents possible shift errors on the other.
BMW was the first car maker to offer this type of gearbox back in 1996. In close collaboration with Getrag and Sachs, BMW M (the high-performance division) has transferred this motorsport experience into applications for everyday road use. Keeping ahead of rivals, BMW has now developed a new high-performance driveline concept which, in its second generation, is known as the “sequential M gearbox” (SMG II). The latest M3 uses this advanced transmission.
It was as early as 1996 that BMW M, as the world’s first supplier of an all-automatic manual gearbox, took centre stage and went on sale with the SMG exclusively in the M3. This system established itself very well and guaranteed that, with the M3 predecessor model, almost every other car featured this progressive driveline concept.
The second-generation SMG, significantly upgraded from the first variant, and is technically identical with the regular manual gearbox of the M3 with six forward speeds, is not only operated by means of a selector lever, as in the past, but also offers the driver two rocker switches on the steering wheel. The driver thus has the choice of how he wants to shift gears. It is, above all, shifting by means of the rocker switches that contributes to increased active safety, as the driver can keep his hands on the steering wheel at all times.
This new SMG gearbox which combines both the option of sporty sequential shifting and the ease of automated shifting offers many benefits and the “drivelogic” allows the driver to individually match the SMG’s shift characteristic to his preferred driving habits in eleven driving programs. When downshifting, the engine will automatically double-declutch; operating the clutch and consequently also the clutch pedal are therefore no longer necessary and, unlike an automatic gearbox, there is no energy-consuming and performance-degrading torque converter either.
BMW says that there is ‘a markedly increased pleasure of shifting’, as the SMG in the sequential mode can be up and downshifted instantaneously and thus produces a realistic “Formula 1 experience”. Compared with a manual gearbox, there are slightly better and, above all, fully reproducible ride performance values and the fact that the driver no longer needs to concentrate on gear changing with this gearbox makes for precise, safer and more relaxed motoring. With the sequential M gearbox, it is easier to benefit from the high power reserves of the M3 through selection of the optimum shift point with “shift lights” (LEDs in the cockpit indicating the optimum shift point on the tachometer).
The second generation of the SMG gearbox stands out owing to its even shorter tractive power interruption – the time required for the fastest shift operations is merely 80 milliseconds. Hardly anyone would be able to change gears manually within such a short period of time. Furthermore, owing to Drivelogic, the M3 driver, benefiting from sequential shifting, is able to manually match the shift dynamics to his individual driving habits in six different programs – ranging from a balanced dynamic program (S1) to a very sporty (program S5). Finally, the driver can also choose the S6 program when the DSC system (dynamic stability control), which comes as standard with the M3, is deactivated. In that case, the SMG will shift at gear change times matching the sporting performance of a true race car.
The new M gearbox also enhances safety. In critical driving situations, such as when downshifting on slippery pavements, the clutch is released instantaneously. In the case of excessive engine drag torque, the car will not break away at the driving wheels. This will eliminate shift errors by the driver.
