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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.
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Encyclopedia
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, DCTs have been configured which shift more quickly than Formula One and other cars equipped with single-clutch AMTs (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.
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 seven-speed version that uses dry clutches, like those usually associated with manual transmissions, has been introduced by VW in the 2008 Golf and Jetta (product codename DQ200). Getrag has a dry DCT under development, and others are rumored to be in development by several manufacturers.
This type of gearbox was invented by Adolphe Kégresse just before the outbreak of World War II, but he never developed a working model. The first actual DCTs 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.
Manufacturers
Mercedes
As of Nov 2008 Mercedes Benz announced a new seven-speed transmission for the redesigned SL63 AMG. The Transmission replaces the traditional torque converter in their 7 speed auto with a multipack wet clutch. It also allows for skipping gears while downshifting rather than progressive downshifting (the driver could go directly from 7th to 4th gear for example). But it is a planetary transmission rather than a twin-clutch gearbox.
Volkswagen
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 of Volkswagen (Golf/Rabbit/Golf Plus, Jetta, Passat and Touran), Audi (A3, Audi S4, Audi S4 Avant 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. UK-based Ricardo Company produces the seven-speed DCT for the Bugatti Veyron 16.4. Lamborghini although owned by VW has a separate "robatized" single clutch transmission which is much like BMW's SMG (Not a dual clutch but no use of clutch pedal).
Getrag
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. Getrag will be providing its DCT in its first commercial applications, for the Dodge Journey and Volvo S40/V50, from mid-2008.
Chrysler
Getrag and Chrysler would have also jointly built a plant in Indiana to supply dual-clutch transmissions to Chrysler starting in 2009, but there is no longer an agreement for it.
In 2008, Chrysler LLC announced Dodge Journey, 2.0L diesel versions of Dodge Avenger and Chrysler Sebring included dual-clutch transmission option in European market.
With Chrysler's merger deal Fiat it is hoped that the dual clutch fiat transmission will make it into fiat models that will be marketed in the USA as Chryslers.
Porsche
Porsche will offer a mass production version of its previously race-only PDK (Porsche Doppelkupplung) transmission on 2009 997 Carrera and Carrera S models. The seven-speed PDK transmission will replace the outgoing Tiptronic transmission. Porsche has additionally announced a separate seven-speed version for the upcoming 911 Turbo. Porsche will also offer the same transmission in the upcoming 2009 Cayman, and Boxster.
Mitsubishi
The Mitsubishi Motors Lancer Evolution X comes with their Twin Clutch SST dual clutch transmission controlled by magnesium paddle shifters.
Nissan
The Nissan GT-R's rear transaxle twin-clutch gearbox also functions as the differential for the car's AWD system. The DCT system was built by BorgWarner, partnered with Nissan's gearbox supplier Aichi.
BorgWarner
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.
On January 14, 2009 BorgWarner announced the establishment a joint venture with the China Automobile Development United Investment Co., Ltd. (CDUI) which is owned by 12 leading Chinese automakers. This joint venture will be known as the BorgWarner United Transmission Systems Co., Ltd., and will be located in Dalian, China. The company will produce various dual clutch transmission modules beginning in 2011.
BMW
In January 2008 BMW introduced a double clutch transmission on their M3 model, manufactured by Getrag and dubbed M DCT (M Dual Clutch Transmission). The same transmission is to be used in the upcoming redesigned Z4 (the Sdrive35i version).
For 2009 models, DCT is an option on the 335i. This is a $1600 option over the manual transmission. The transmission is said to be able to hold 500 NM of torque..
Fiat
Fiat Powertrain Technologies is starting production of Dual Dry Clutch in 2009.
Ferrari
Ferrari will be incorporating a seven-speed dual clutch transmission in to their upcoming California sportscar.
Ford
Ford has released a "Powershift" transmission on the 2008 Ford Focus (international)
. This was designed with gearbox specialist Getrag under the GETRAG FORD Transmissions group founded in 2001 and is expected to feature in other Ford and Volvo models. Ford has announced the US-market version of the Mk. 7 Ford Fiesta coming in 2010 will feature the "Powershift" transmission. Ford also announced the introduction of PowerShift transmission to North American market by 2010.
The Volvo version 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 more sporty cars.
General Motors
In the company's restructuring plan, it revealed that dry dual clutch transmission would be available in 2012 calendar year.
saab 1995 900s
Hyundai
In 2009 Geneva Motor Show 2009, Hyundai unveiled Hyundai ix-onic concept car, which features 6-speed double-clutch transmission.
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