Through The Gears ... Without A Pedal
Sydney Morning Herald
Friday August 1, 1997
Hydraulics and clever software
do the job of the clutch in BMW's sequential gearbox. PETER McKAY says the technology will spread.
Has the ultimate driving car, the smooth yet raunchy BMW M3, gone soft, lost its clutch pedal and added an autobox?
Not quite. BMW's engineers insist the Sequential M Gearbox is not an auto, and they're right of course, despite the accelerator and brake pedals on one of the world's great high-performance cars not having a third pedal for company.
Like the Ferrari F355's Formula One-style "power train management" system, the SMG is a six-speed manual gearbox controlled by an electro-hydraulic actuator system which performs many of the functions normally carried out by the driver.
The clutch is activated not by the driver's left foot but by hydraulics and clever software, and the H-pattern shift is consigned to the dustbin of history.
BMW prides itself on its engineering inventiveness. The M3 SMG - heading to a showroom near you - is intended to take driving to a new, higher plane.
Its efficiency has encouraged F1 and Super Touring engineers to swing away from clutch-pedal-and-gear-lever shifts to swifter, less energetic, mistake-free computer-generated gear changing, using (in the case of GP cars) steering-wheel-mounted paddles or switches, or sequential changing.
Purists who enjoy the challenge of sweet gear changing - working clutch, accelerator and gear lever in symphony - may decry the move to an easier way. But BMW and Ferrari believe these systems are the way of the future and are destined for mass use.
In Europe, where the optional SMG system has been on sale for eight months, the take-up rate has reached 60 per cent in Italy and Spain, and 40 per cent in the Father-land. Here, BMW expects a similar demand, despite the $4,500 premium on the M3 manual's $131,750.
On the BMW's console, the driver selects E for economy and fully automatic operation, or S for sequential or sport, a do-it-yourself mode which requires a backward pull on the spring-loaded shifter to change up or a forward push to downshift - just like the drivers in the AMP Bathurst 1000 on October 5. It's changing gears in a straight line, sequentially. Motorcyclists have been operating this way for yonks, albeit using one foot.
BMW experimented with several locations for the lever, but decided the console was most practical. Computer control of the operation means that even the most ham-fisted of drivers can't do too much damage.
At Phillip Island racetrack this week, we tried to fool the SMG in many different ways, all in vain.
In the economy program, shift points vary according to the way the car is being driven. Move to the sporty mode and the computer senses action. The shift becomes fast yet harsh, like a racing car. You can skip gears - say, from fifth to second - just by pushing the lever quickly three times.
Riding the clutch pedal is impossible, as is stalling the engine or crunching cogs. The SMG refuses to shift down if the engine is at risk of over-revving, and returns automatically to first gear when you stop. These attributes mean components last far longer than usual.
The SMG holds gears right to the redline under maximum acceleration, a tell-tale orange light on the dash alerting the driver it's time to upshift.
When downshifting early, even on slippery roads, it's impossible to lock the rear driving wheels; sensors re-open the clutch automatically.
And should the M3 oversteer dramatically, causing you to lift off the throttle, sensors cause the clutch to re-open, mirroring the technique of some race drivers.
Revhead BMW owners may care to know that, yes, you can still do tyre-smoking starts with the sequential 'box. Push the sequential lever forward, hold it there, build up the appropriate revs ... and release the lever. Blast off.
© 1997 Sydney Morning Herald
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