Lucky Number Seven

Getrag GMBH & CIE KG Becomes the latest high-profile player in the dual-clutch-transmission segment as BMW AG and Ferrari Automobiles SpA rush to incorporate the German supplier's new drivetrain technology in their newest performance cars.

Many praise-worthy headlines are to be expected of these new transmission systems, which deliver more than ever the performance benefits of a sequential-manual gearshift with the smoothness of a conventional torque-converter automatic.

Rushed is the wrong word to describe the similar DCT system Porsche AG developed with ZF Friedrichshafen AG for the '09 911. The German auto maker originally planned to launch the 7-speed PDK (Porsche-Doppelkupplung) gearbox with the release of the current 997-edition model, but “development issues” delayed the program by at least three years.

However, rushed correctly applies to Getrag's 36-month development for its two all-new DCT gearboxes, which debut in the BMW M3 this fall and upcoming '09 Ferrari California.

The new 7-speed transmissions — 7DCI600 for the M3 and 7DCL750 for the California — were developed in parallel, but according to Stephan Rinderknecht, Getrag's head of research and development, “They were independent programs; there are no common parts.”

To broaden the 7DCI600's appeal, Getrag offers the gearbox in two basic forms, both capable of accepting up to 443 lb.-ft. (600 Nm) of torque.

For the M3, the high-speed version offers a ratio spread (between first and seventh gears) of 4.8, with a direct top gear that permits 9,000 rpm.

The alternative variant (yet to be seen on a production car), in which fifth gear is direct and sixth and seventh are overdrive gears, offers a planned ratio spread of 6.7, although this could stretch to “beyond 7.0.”

Because the overdrive ratios would increase prop-shaft speeds to well over 10,000 rpm, this version is limited to engine speeds of 7,500 rpm.

“The main focus in the development was a superb level of economy,” Rinderknecht says.

In the M3, the high-speed DCT delivers a 5% fuel-economy improvement over a 6-speed automatic. However, Rinderknecht claims the wide-ratio gearbox carries at least a 10% advantage.

“We also wanted to offer flexibility between comfort and sporting (gear) shifting and to allow short shifting in low-speed driving, so that it is capable of performing at virtually the (same) level as an automatic gearbox.”

Still, he admits software upgrades to further improve low-speed smoothness already are in the pipeline.

The M3 is just the first of many high-performance, front-engine/rear-drive cars to use the new 7DCI600 transmission, called M-DCT by BMW.

Getrag's factory, 31 miles (50 km) north of Stuttgart, which produces the new gearbox, is set up to allow a “flexible concept on volumes,” Rinderknecht says, noting the factory architecture allows for a production of 100,000 units per year.

Because the M3 only is expected to absorb about 15,000 units annually, and the addition of a DCT option for certain '09 3-Series models won't take up the remaining capacty, that leaves plenty of room for other programs.

However, the BMW M5 and M6, which currently are saddled with the oft-criticized single-clutch SMG automated manual, will have to wait until their next iterations to sport a DCT, despite the new gearbox's ability to cope with the 5.0L V-10's 384 lb.-ft. (520 Nm) of torque.

Getrag's dual-clutch transaxle unit for the Ferrari California is more robust than the BMW version and capable of absorbing 553 lb.-ft. (750 Nm) of torque. This is far beyond the maximum torque of Ferrari's latest V-8 powertrain, which is expected to produce in the California slightly more than the F430's 343 lb.-ft. (465 Nm).

It, too, is capable of extreme revs — 9,000-plus rpm, which is well above the 7,500-rpm maximum permitted by even the best conventional automatic — yet manages a range of ratio spreads from 4.7 to 6.1.

The Ferrari gearbox is built in much lower numbers of between 5,000 and 10,000 annually.

“We expect further customers, because it offers important advantages over an automatic at high revs,” says Rinderknecht.

As such, it's not hard to imagine the gearbox becoming standard on all Ferrari road cars, much like how carbon-ceramic disc brakes have proliferated through the auto maker's lineup.

Getrag's involvement with DCTs dates back to the early 1980s, when the supplier worked with Porsche on PDK gearboxes for its 962 Le Mans prototypes.

Rinderknecht admits inadequate electronics slowed joint-development programs with Ford of Europe in 1996 and 1997.

“It was clear that technology was not ready for the product,” he says “The ECU (electronic control unit) processor simply was not fast enough.“

Without a firm commitment from an auto maker, Getrag could not devote the necessary resources to proceed with the development on its own.

It was the Direct Shift Gearbox (DSG) breakthrough by Volkswagen AG and BorgWarner Inc. in late 2003 that provided the impetus to move beyond the crude, single-clutch robotized manuals that slowly gained popularity in the late 1990s.

“It was always a problem for us, so we were happy that VW took the system and proved it could work. It opened up the complete market,” Rinderknecht says.

VW worked on the technology for more than 15 years before introducing the first 6-speed DSG in 2003.

Among the auto maker's brands, VW, Audi, SEAT and Skoda all offer the feature, as well as the Bugatti Veyron and its unique Ricardo plc-developed 7-speed version.

VW built 400,000 DSG gearboxes in 2007 and recently increased daily output to 1,750 units to keep up with demand.

Earlier this year, the auto maker released a 7-speed version (DQ200), which uses a pair of dry clutches vs. the 6-speed's wet clutches, providing an improvement in efficiency, simplicity and performance in low-power applications.

A high-torque, 7-speed DCT with wet clutches will debut later this year on several high-performance Audi AG models under the S-tronic label.

In addition, Getrag currently has high-volume deals for dual-clutch gearboxes with Ford Motor Co., Volvo Cars, Chrysler LLC and Mitsubishi Motors Corp.

Combined with new transmissions continuing the charge in two of the most-storied nameplates in sports-car history, DCTs surely are destined to become de rigueur in more performance vehicles over the next decade.

The Endangered Clutch Pedal
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