The changing face of the gearboxe in your car

EVERYONE one has heard claims about Formula One technology finding its way into the real world: Car-makers have always been keen to exploit any chance of linking their mundane road cars to the glamorous domain of motor sport.

The arrival of BMW's sequential transmission (SMG) is about as close as any of these claims have come to reality.

Like a Formula One gearbox, BMW's system, as used on the latest version of its high-performance M3 coupe, makes what is basically a conventional transmission about as slick-shifting, efficient and user-friendly as is possible.

Dispensing with the normal clutch pedal and minimizing the gearshifting chore to just a backward or forward flick of the wrist, the SMG system manages to retain the precise control and maximum efficiency of a manual gearbox and combine it with the lazy action of a regular automatic.

Why, the SMG can even be switched to a full-automatic mode that lets the system do all its upshifting and downshifting without any help from the driver.

It looks a better proposition than a normal automatic gearbox in many ways: It weighs little more than a normal manual gearbox, and does not lose power and economy to the fluid-coupled torque converter used in a regular automatic.

The M3's six-speed sequential gearbox has basically been contrived -- as in a Formula One car -- to make fast driving easier, while still providing full driver control over the shifting process and ensuring maximum power is transferred through to the road.

Fundamentally, BMW's SMG is a normal gearbox, complete with clutch -- except the clutch is operated not by the driver but by an electronically controlled hydraulic actuator.

The shifting of gears is also electro-hydraulically controlled -- the shift lever has no mechanical connection to the gearbox.

Modern electronics, with sensors reading various parameters such as accelerator position, engine revs and brake operation, have enabled BMW to design a system that is far advanced over the simple "clutchless" manual transmissions used decades ago by car- makers such as VW, Renault or Porsche.

And although it might appear so at first glance, BMW's system bears no similarity to the "Tiptronic" gearbox used by Porsche, or the similar system available in the Honda NSX.

These are basically regular automatic transmissions with the benefit of a little more control over the shifting process being available to the driver.

They use "planetary" gearsets, along with the power and economy-robbing "torque converter" that is the signature of a normal auto.

The SMG's closest cousin today is the "Sensonic" transmission used by Swedish car-maker Saab.

The big difference is that although clutch actuation is electro-hydraulic, the Saab system uses a regular H-pattern shift lever and offers only manual operation.

The really clever thing about the BMW's new-generation sequential gearbox is that while it provides full manual shifting up and down, in automatic mode it performs all shifting tasks without any input from the driver.

It is a full automatic, but with the crisper shifting and minimum energy loss of a manual.

The only downside is that the shifting can, in trying situations, be harsher than an automatic and not as smooth as what could be achieved by an expert manual-transmission driver.

And that's the nub of what may turn out to be a dilemma for aspiring BMW M3 buyers -- whether to forego the challenge and rewards of a sweet-shifting, regular manual gearbox, or to wimp out with a transmission that taxes driving abilities less while retaining levels of efficiency not possible with a full automatic.

The sequential gearbox is indeed a marvel and some say the principle might eventually find its way down to the bottom end of the market where its efficiency and minimal sapping of engine power would have appeal to small-capacity, economically inclined powerplants.

Economies of scale will decide whether the technology will remain exclusive to the high end of the market; if enough people accept the SMG, then the costs of manufacture might drop sufficiently to make it available to the masses.