Twin-clutch gearbox

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A twin-clutch gearbox, double clutch transmission or dual clutch transmission (DCT) is a semi-automatic transmission with separate clutches for odd and even gears. The outer clutch drives the odd numbered gears, while the inner clutch drives the even numbered gears. Shifts can be accomplished without interrupting power, by applying the engine's torque to one clutch just as the engine's torque is being disconnected from the other clutch. Since the synchronizers that select an odd gear can be moved while driving the car in an even gear, and vice versa, DCT's have been configured which shift more quickly than Formula One and other cars equipped with single-clutch AMT's (automated-manual transmissions, a.k.a. single-clutch semi-automatics). Also, with a DCT, shifts can be made more smoothly than with an AMT, making a DCT more suitable for street-driving.^[1]

A twin-clutch gearbox eliminates the torque converter used in traditional automatic transmissions. Instead, dual clutch transmissions that are currently on the market use wet multi-plate clutches, similar to the clutches used in traditional automatic transmissions. A 7-speed version that uses dry clutches, like those usually associated with manual transmissions, will be introduced by VW in the 2008 Golf and Jetta (product codename DQ200). Getrag has a dry DCT under development^[2], and others are rumored to be in development by several manufacturers.^{[citation needed]}

This type of gearbox was invented by Andolphe Kégresse just before the outbreak of World War II, but he never developed a working model. The first actual DCT's came along in the 1980s when computers to control the shifts were compact enough: the PDK (Porsche Doppelkupplung) used in the Porsche 956 and 962 Le Mans race cars and the Sport Quattro S1 race car.^[3]

[edit] Manufacturers

As of late 2007, DCTs are sold mostly by Volkswagen Group under the brand names DSG Direct-Shift Gearbox (for Volkswagen, SEAT, Škoda and Bugatti) and S-Tronic (for Audi). Volkswagen produces a DCT transmission (model DQ250) under license from Borg-Warner for use in transverse powertrain installations, and this is used in a wide range Volkswagen (Golf/Rabbit/Golf Plus, Jetta, Passat and Touran), Audi (A3 and TT), SEAT (Altea, Leon and Toledo) and Škoda (Fabia, Octavia and Superb) models. Volkswagen are believed to be developing a family of DCTs to be used across the full VAG product range, including longitudinal powertrains.^{[citation needed]} UK-based Ricardo Company produces the seven-speed DCT for the 1001-horsepower Bugatti Veyron 16.4.

Getrag has developed a complete range of DCT transaxles, including 7DCL750, a seven-speed transaxle for mid-engine longitudinal applications, capable of taking more than 750 N·m.^[4] Getrag will be providing its DCT in its first commercial applications, for the Dodge Journey and Volvo S40/V50, from mid-2008.^[5] Getrag and Chrysler will also jointly build a plant in Indiana, to supply dual-clutch transmissions to Chrysler starting in 2009.^[6] The Volvo transmission will be called Powershift and will be built in Koping, Sweden at Volvo's transmission plant. The powershift gearbox will be introduced on the second generation Volvo S60 and then on to the V50 and C30 models. The XC60 is expected to get this Powershift gearbox along with other new models to make a more sport car.

A renewed version of the PDK (Porsche Doppelkupplung), but for mass-production instead of race cars, was expected in January 2006 but may come in 2008 or later. Porsche is said to have filed paperwork indicating that it will be available as a late addition to the 997, in future model-years.^{[citation needed]} [1]

Mitsubishi Motors has announced that the 2008 Lancer Evolution X will come with their Twin Clutch SST dual clutch transmission controlled by magnesium paddle shifters.^[7]

The Nissan GT-R's rear transaxle twin-clutch gearbox also functions as the differential for the car's AWD system.

BorgWarner is the current leading supplier of wet clutches and hydraulic modules for these transmissions. BorgWarner, who call their technology "DualTronic", signed further agreements with three other (unnamed) European automotive manufacturers to incorporate their components in DCTs.^[8]

In January 2008 BMW announced the introduction of a double clutch transmission on their M3 model, manufactured by Getrag and dubbed M DCT (M Dual Clutch Transmission).

Fiat Powertrain Technologies is starting production of Dual Dry Clutch in 2009.^[9]

Ferrari will be incorporating a 7-speed dual clutch transmission in to their upcoming California sportscar.

Ford have released a "Powershift" transmission on the 2008 Ford Focus (international)^[10] . This was designed with gearbox specialist Getrag under the GETRAG FORD Transmissions group founded in 2001^[11] and is expected to feature in other Ford and Volvo models.