GM’s DCT Intro Doubtful By 2012
GM has lagged behind European OEMs that have introduced swift-shifting, dual-clutch transmissions over the past several years.
January 12, 2010
Special Coverage
North American Int’l Auto Show
DETROIT – While some auto makers are embracing swift-shifting dual-clutch transmissions for performance cars, it appears General Motors Co. will remain wedded to conventional 3-pedal manual configurations for the foreseeable future.
The viability plan GM filed last year as part of its bankruptcy case said the auto maker planned to introduce a dual-clutch transmission in 2012. But Tom Stephens, vice chairman-global product operations, suggests the DCT will not come until later.
“I don’t think 2012,” Stephens tells Ward’s on the sidelines at the North American International Auto Show here.
“We've had to call the shots on where we spend the money," Stephens says when asked why GM is lagging behind European auto makers that have introduced DCTs – to rave reviews – over the past several years.
A DCT connects two separate gear sets, with even-numbered gears on one shaft and odd-numbered gears on another, to the engine by two parallel clutches. When one gear is engaged, the next gear, thanks to the second clutch, is pre-selected, ready for swift engagement.
In a separate roundtable media interview, Vice Chairman Bob Lutz says, “We have plans for a DCT,” and that it will be introduced “in due time.”
Lutz says he considers a DCT to be equivalent with a conventional 3-pedal manual. However, the computer-controlled dual-clutch enables shifting that is much faster and smoother.
On Monday, GM unveiled a high-performance Buick Regal GS that arrives in showrooms by this summer, and the sole gearbox is a 6-speed manual. Initially, the car will be imported from Russelsheim, Germany, but North American production is slated for first-quarter 2011 at GM’s Oshawa, ON, Canada assembly plant.
Lutz says GM will have DCT “in due time.”
The Regal GS show car has a 2.0L turbocharged direct-injection gasoline 4-cyl. tuned to 255 hp and 295 lb.-ft. (400 Nm) of torque.
Lutz says GM wants to produce a DCT that requires no hydraulic fluid – a task that creates certain technological challenges. A dry-clutch DCT is less expensive to manufacture, while a wet-clutch configuration is more expensive than a conventional automatic, he says.
Problem is, dry-clutch DCTs are “torque-limited,” Lutz says.
“Anything over 1,600 to 1,800 CCs (1.6L to 1.8L in engine displacement) won’t work with a dry-clutch DCT. Since most of our engines are 2.0L or 2.4L or above, we have to either envisage a wet-clutch DCT or figure out a way to get the torque capacity of dry-clutch DCTs up. That’s what we are wrestling with now.”
Until GM can crack that problem, 3-pedal manuals appear to be the gearbox of choice for the auto maker’s performance cars.
“For an automobile to be taken seriously by the enthusiast media, it pretty much has to offer a manual transmission,” Lutz says.
“Whether you sell very many that way or not is almost immaterial. It’s a fact that you’ve done it, you’ve demonstrated you can do it, and the car with the manual transmission is there for those who really want it.”
GM spokesman Tom Read says the auto maker for now is working without a supplier partner on the DCT, and that GM’s existing second-generation 6-speed automatics boost efficiency 5% when mated to both 4-cyl. and 6-cyl. engines in front-wheel-drive applications.
Rival Ford Motor Co. already offers its PowerShift dual-clutch transmission in its European Focus C-car that pairs a twin wet-clutch system with a 2.0L turbodiesel engine.
In North America, Ford’s 6-speed dual-clutch PowerShift gearbox will be available in the upcoming Fiesta and Focus small cars. In both applications, a dry-clutch derivative of the PowerShift transmission will be employed, requiring no oil pump or torque converter.
Ford’s partner on the PowerShift gearbox has been Germany’s Getrag GmbH & Cie KG.
German auto makers pioneered the DCT, arriving first in the Volkswagen Golf R32 and Audi TT in early 2003. The TT was the first vehicle to reach the U.S. with the DCT, later that year.
Drivetrain specialist BorgWarner Inc. developed the gearbox, alongside VW engineers.
Since then, the technology has been driving a wide range of applications, including the New Beetle, BMW M3 and Z4 roadster, Nissan GT-R, Mitsubishi Lancer Evolution and Porsche Boxster, Cayman, Carrera and Panamera.
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