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New car reviews

2005 BMW 530i

Shifty behavior

Marc Stengel, Wed, 7 Sep 2005 08:00:00 PDT

There's nothing new about driving techniques. There are new automotive technologies, to be sure-gas-electric hybrids, futuristic diesels, variable-valve timing and so forth. But these don't require any new driving skills.

And there are new electronic, or "telematic" innovations; but mastering these is more a function of managing multi-tasks than of learning new skills. The telematic challenge is to prevent drivers and passengers from hurtling into oblivion at the behest of attention-diverting gadgets. This has nothing to do with such driving skills as double-clutching, for example, or throttle-steering.

So what's with this new Sequential Manual Gearbox {SMG) that trespassed into my purview last week, lurking like a stowaway aboard BMW's 530i sedan? Although it's not the first SMG I've encountered (see last year's impressions of an Audi TT Roadster similarly equipped), it is a very new and untraditional transmission technology that forces a driver-an enthusiast driver, at least-to adopt a new driving technique otherwise unsuited to manual or automatic transmissions.

It is appropriate that BMW should offer an SMG option ($1,500) for its classy 530i sedan. Not only is this car the putative benchmark and trend-setter for the mid-size luxury sedan category but it is also the only car of its type able to satisfy all transmission tastes. In other words, there are three different six-speed gearboxes available with the 530i: a traditional six-speed manual; a traditional six-speed automatic with "StepTronic" clutchless-shifting; and a non-traditional six-speed sequential manual gearbox.

It bears digressing a moment, at this point, to rehearse the principle of shifting gears required to drive a car. In consideration of the fact that an automotive engine-in this case a 225-horsepower twin-cam straight-six-has a relatively fixed rpm range for making usable power, a selection of different gears is required to spread that power over a range of real-world driving speeds. Low gears, for example, address the "start-from-a-dead-stop" scenario. Higher gears provide "roll-on" acceleration for, say, passing slower vehicles at highway speeds.

Gear selection also plays a part in slowing, even halting a vehicle. Shifting down a gear at cruising speeds induces the engine, rather than the brakes, into retarding a vehicle towards a lower, therefore slower rpm range. Anyone who's ever missed a shift by selecting second when fourth was expected will recognize the unforgettable lurch that inevitably results.

The point is that gears are essential to modulating a vehicle throughout a complete, versatile range of speeds; and, knowingly or not, every driver uses gearing whenever he or she gets behind the wheel. Adepts with a manual make their own gear selections according to their preferences. Drivers of automatic transmissions let the transmission itself, with its feedback systems, select the gear deemed most appropriate for a given circumstance.

There's even a contemporary trend for automatics to "share" control with drivers via clutchless or "manumatic" features like StepTronic. Left alone, StepTronic is indistinguishable from a pure automatic; but when a driver demands a specific gear, a tap of the shifter overrides the automatic's "brain" and selects the gear requested. Manumatic control, however, is but a clever illusion. The automatic transmission remains in charge and merely flatters "the boss" that he or she is in control.

Not so with SMG technology. Derived from the uncompromising conditions of high-tech motor racing, SMG puts a clutch-activated manual transmission at the driver's disposal, yet dispenses with the clutch pedal. It's as if an invisible, robotic left leg were assisting with the time-honored two-step of synchronizing accelerator and clutch pedals at every gearshift.

Indeed, the SMG experience is an uncanny-and therefore slightly disturbing-facsimile of the traditional manual shift. Using either a traditional "stick" gearshift in the center of the floor console or a pair of "Shrek-eared" paddles on the steering wheel, the driver accelerates from first to second with a tap. In response, the engine drops its revs (as if the driver had backed off the accelerator); the gear changes; and the revs climb again (as if the driver were tipping the accelerator into the next gear). For downshifts, the opposite occurs: the engine blips the revs to a slightly higher level; the gear drops; and the engine falls to lower revs.

The entire process is a syncopated, sing-songy affair, so different from either manual or automatic shifting that new driving habits are required. For one thing, a driver must anticipate the SMG's usurpation of accelerator control during up and down shifts, and that means timing taps on the paddle shifters so that gear changes don't happen at awkward places-such as deep into a high-speed corner where shifting is an eternal, unforgivable no-no.

For another thing, it means constantly monitoring a dashboard display indicating what gear is selected, since there's no sense of shifter position as with a traditional shifter. Grizzled vets with their eyes on the road can merely brush a gear shifter with a little finger to know what gear they're in; SMGers have to look to be sure, at which point they're not eyeing the road.

And whereas SMG will take over all shifting tasks should the driver abandon this responsibility altogether, it does so reluctantly. Unlike a true automatic, SMG's "driverless" shifts are characteristically lurching and spontaneous, as if to chide a driver for not taking his duties more seriously. In other words, it's better just to shift all the time-up and down-and to learn how to do it right (with left foot immobile, at that).

All of which is to say, I suppose, that an old driver-dog can learn new tricks, but the trick had better be worth it. In the case of SMG shifting, I'm put in mind of a 20-foot steam-powered tricycle. It's a technical marvel, without question; but what's it good for?

2005 BMW 530i; 4-door, 5-pass.; 3.0-liter DOHC inline-6 w/"VANOS" vvt; RWD, 6-sp. SMG; 225 hp/214 ft.-lbs.; 20 mpg/city, 29 mpg/hwy w/ premium; trunk: 14 cu. ft.; base price: $45,400; as-tested, w/ 4-wheel ind. suspension & ABS disc brakes, "Logic 7" AM/FM/CD/satellite-ready audio, 18-in. wheels & sport pkg., rain-sensing wipers, front/front-side/front-rear curtain airbags: $57,820.

 

 


2005 BMW 530i


2005 BMW 530i

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