Dual-clutch transmission

Design

The fundamental principle of a DCT is that one clutch drives a gear-set for the even-numbered gears, while the other clutch drives the odd-numbered gears. Since the DCT can pre-select an odd gear while the vehicle is being propelled in an even gear (or vice versa), DCTs can shift several times faster than is possible with a manual transmission. By timing the operation of one clutch to engage at the precise moment that the other is disengaging, a DCT can shift gears without interrupting the torque supply to the wheels.

A DCT uses clutch packs (as per a manual transmission), rather than the torque converter used by traditional (hydraulic) automatic transmissions. Wet-clutches are bathed in oil to provide cooling for the clutch surface, therefore wet-clutches are often used in applications with higher torque loads, such as the 1250 Nm engine in the Bugatti Veyron.

Several arrangements for the two clutches are possible, and are outlined below:

• Most automotive DCTs use two concentric clutch packs located on the same axis as the flywheel. Therefore, the outer clutch pack has a larger diameter than the inner clutch pack.
• Many DCTs for tractors (such as the Fortschritt ZT 320) use a similar arrangement where the clutches are located on the same axis of the flywheel. The difference is that the clutches are at different positions on this axis (i.e. one in front of the other) and the same size as each other. This design is used by the Tremec TR-9070 DCT used by the 2020 Ford Mustang Shelby GT500.
• Another design (as used by the Volkswagen DQ200 transmission) arranges two identical-size clutches located side-by-side. This design requires two side-by-side input shafts, which are driven from the crankshaft via gears.

History

| M: Motor | A: Primary drive and driving shaft | B: Dual clutch | C: Driven shaft | D: Layshaft, hollow, even gears | E: Layshaft, odd gears | F: Output

The concept of a dual-clutch transmission was invented by French engineer Adolphe Kégresse in 1939. The transmission was intended for use in the Citroën Traction Avant, however Kégresse ran out of money before a working model could be developed.

One of the first production DCTs was the Easidrive unit developed in the late 1950s by United Kingdom's Smiths Industries and Rootes. This DCT – introduced on the 1961 Hillman Minx (Series IIIC) – used two electro-magnetic clutches, along with analogue electronics and a series of solenoids to implement the gear shifts. The Easidrive was offered as an option on Hillman and Singer models, however it was not a reliable device and many were replaced by conventional manual transmissions.

Porsche began development of DCTs for racing cars in the late 1970s, due to the possibility of a DCT preventing a drop in boost during gear shifts on a turbocharged engine. As the electronics required to control the transmission became compact enough to be practical, the Porsche Doppelkupplungsgetriebe ('dual-clutch gearbox') (PDK) transmission was installed as a prototype in a Porsche 956 Le Mans racing car in 1983. The first use of a PDK in competition was the 1985 Porsche 962 C Le Mans racing car, which won the World Sportscar Championship in 1986. The PDK transmission was also used in the 1985 Audi Sport Quattro S1 Group B rally car.

The first mass-production passenger car to use a DCT was the 2003 Volkswagen Golf R32.

Manufacturers

; BorgWarner BorgWarner produced the first mass-production DCT, as used in the R32 model introduced to the Volkswagen Golf range in 2003. and produced various components for the 2007 Nissan GT-R sports car, an early application for DCTs involving high torque loads. The company supplies several car manufacturers with complete transmission units, wet-clutches and/or mechatronic control modules.

; Getrag Getrag began production of DCTs in 2008 and has supplied manufacturers including BMW, Dacia, Dodge, Ferrari, Mercedes-Benz, Ford, Mitsubishi, Renault, Smart and Volvo. The Getrag 7DCL750 is a 7-speed DCT which is designed for high-performance engines and has a torque rating of 750 Nm. It is used in mid-engined sports cars such as the 2009 Ferrari 458, the 2014 Mercedes-AMG GT and the 2017 Ford GT.

; Honda Honda manufactures DCTs for some Honda motorcycles as of 2024, and was the first to add a DCT to motorcycles. Honda also previously manufactured DCTs for some Acura cars.

; HYUNDAI TRANSYS HYUNDAI TRANSYS manufactures dry 7-speed and wet 8-speed DCTs as of 2024. The DCTs are used in some Hyundai and Kia (e.g. Ceed) vehicles.

; LuK LuK DCTs have been used by Volkswagen Group since 2008, in several smaller cars with relatively low torque outputs.

; Ricardo Ricardo designed and built 7-speed DCT used by the 2005-2015 Bugatti Veyron, which has a turbocharged 16-cylinder engine producing 1250 Nm of torque.

; Stellantis Stellantis manufactures the electrified dual-clutch transmission (eDCT) at the Mirafiori Automotive Park in Italy as of 2024.

; Tremec Tremec provides the 8-speed DCT used in the 2020 Chevrolet Corvette C8 and the 7-speed DCT used in the 2020 Ford Mustang Shelby GT500.

; ZF Friedrichshafen ZF Friedrichshafen produce the 7-speed DCT used by Porsche (marketed as PDK).

Usage in motor vehicles

Following its 2003 introduction in the Volkswagen Golf R32, a 6-speed DCT (model code DQ250), with two wet-clutches arranged concentrically, has been used in several Volkswagen and Audi models.

Usage in high performance cars began in 2005 with the 7-speed DCT used in the Bugatti Veyron. Other early high performance applications include the 2007 Nissan GT-R, the 2008 Ferrari California, the 2008 Mitsubishi Lancer Evolution X and the 2009 Porsche 911 (997).

The 2009 Honda VFR1200F is the first motorcycle to use a DCT. Honda has since expanded the application of the DCT to the Gold Wing model (model year 2018), the Africa Twin, the NT1100, Rebel 1100, and the NC700XD (model year 2012).

In 2010, the Mitsubishi Fuso 6-speed Duonic transmission became the first DCT to be used in a truck.

The 2015 Acura TLX uses a torque converter (a device typically used in hydraulic automatic transmissions) paired with its 8-speed DCT. The purpose of the torque converter is to improve the smoothness of low-speed driving, through the elimination of jolting and shuddering sometimes found in DCTs at low speed.

Usage in tractors

Several 1970s tractors from eastern European countries (such as the Kirovets K-700 derivatives) used manually operated DCTs. For example, the Fortschritt ZT 300 has an Unterlastschaltstufe ('shifting under load') function, which needs to be pre-selected by the driver and then activated by pressing the clutch halfway down. This engages the second clutch, which applies a reduction gear to the driven wheels without any interruption in the torque transmission to the wheels.

Usage in railcars

A different type of dual-clutch transmission has been used in some railcars. The two clutches are placed one on the gearbox input shaft and the other on the gearbox output shaft. To make a gear change, both clutches disengage simultaneously and a brake inside the gearbox engages. The gearchange occurs with all gears stationary, so no synchronizing mechanism is needed. After the gear change, both clutches re-engage. There is a significant break in power transmission, so this system is unsuitable for shunting locomotives.

References

References

1. (September–October 2003). "Powertrain — transmissions: Shift in power to the gearbox". UnofficialBMW.com.
2. (June 2009). "Automatic-shifting dual-clutch transmissions are poised to grab share from traditional transmissions thanks to their combination of efficiency and convenience". DCTfacts.com.
3. "Porsche Doppelkupplung (PDK)". Porsche.com.
4. Fenske, Jason. (July 8, 2019). "Here's How the Koenigsegg Jesko's Seven-Clutch Gearbox Works".
5. (August 19, 2022). "Holy Shift! Koenigsegg's Wild Manual Transmission Has 7 Clutches—and an Automatic Mode".
6. Colwell, K.C.. (14 September 2019). "Koenigsegg's New Light Speed Transmission Promises Ultraquick Shifts". [[Car and Driver]].
7. "Wet-Clutch or Dry-Clutch?". The Lubrizol Corporation.
8. "Two Clutches, No Waiting".
9. "ZT300 doppelkupplung image".
10. "TREMEC Introduces New 7-Speed Dual Clutch Transmission".
11. "How dual-clutch transmission works".
12. (6 April 2006). "How Dual-clutch Transmissions Work".
13. "Easidrive".
14. (7 July 2014). "A Useful Text-Book - The Motor Vehicle".
15. "The PDK Transmission".
16. (10 December 2013). "Shift This: A History of Porsche's Sportomatic, Tiptronic, and PDK Transmissions".
17. (10 May 2010). "Porsche 956".
18. (22 January 2018). "Here's What the Porsche PDK Gearbox Means".
19. (13 March 2009). "Dual clutches take the lead". Findlay Media Ltd.
20. "The Porsche Transmission". Lüfteknic.com.
21. (21 January 2008). "The 7-speed DSG — the intelligent automatic gearbox from Volkswagen". [[Volkswagen AG]].
22. (11 March 2009). "Dual-Clutch technology voted Transmission of The Future at CTI Symposium". Gordon Communications.
23. Sutton, Mike. "BorgWarner Refining DCT Technology". Wardsautoworld.com.
24. Lewin, Tony. (17 September 2007). "Getrag's dual-clutch transmissions to take off". Crain Communications, Inc..
25. Robinson, Peter. (2008-07-28). "Getrag Jumps Into DCT Fray With High-Performance Applications". Subscribers.wardsauto.com.
26. (February 2022)
27. Pund, Daniel. (2008-11-06). "2009 Ferrari California First Drive on Inside Line". Insideline.com.
28. (2009-11-10). "2010 Ferrari 458 Italia First Drive". Insideline.com.
29. TIME AGO. (4 November 2009). "2011 Mercedes-Benz SLS AMG Gullwing — Second Drive — Auto Reviews". Car and Driver.
30. (no votes). "Renault Megane CC dual clutch transmission". Eurocarblog.com.
31. "GETRAG Powershift 7DCL750 transmission". GETRAG Corporate Group.
32. (9 November 2018). "The Ford GT's Gearbox Is Shared With the AMG GT, Costs Twice as Much".
33. (13 February 2008). "LuK dual-dry-clutch 7-speed DSG gearbox in volume production at Volkswagen (Group)". Schaeffler Group USA Inc., BÜHL, GERMANY.
34. (April 28, 2020). "The Differences Between a DCT and a Traditional Automatic Transmission | TREMEC Blog: Get Connected".
35. (23 September 2009). "FEATURE: ZF's new 7DT 'Mood-Sensing' Dual-Clutch Transmissions". CSM Worldwide.
36. "ZF in the Porsche 911 Carrera: Porsche Carrera — Versatility with sports car genetics". [[ZF Friedrichshafen.
37. "7-Speed Dual Clutch Transmission".
38. (24 September 2009). "Top 911 moves to industry-standard shift controls". The Lubrizol Corporation.
39. "Porsche Joins the DCT Set". The Lubrizol Corporation.
40. "Volkswagen Service Training Manual 308 — 02E 6-speed DSG".
41. "BorgWarner DCT for Nissan's GT-R". SAE International.
42. "Aichi Kikai manufacturing history". Aichi Machine Industry Co., Ltd.
43. "Ferrari chooses DCT for its latest supercar". The Lubrizol Corporation.
44. (10 July 2007). "Mitsubishi Motors develops S-AWC vehicle dynamics control system & Twin Clutch SST automated manual transmission". Mitsubishi Motors.
45. (2009-05-06). "2008 Mitsubishi Lancer Evolution X MR: Are Shift Paddles for Wimps?". Edmunds Inc..
46. (14 April 2008). "SS-T: The Magic Inside the Evo X". The Motor Report Pty. Ltd..
47. (6 June 2008). "New Porsche 911 with Direct Fuel Injection and Double-Clutch Gearbox". Porsche Cars Great Britain Ltd. / Dr. Ing. h.c. F. Porsche AG.
48. "Porsche Doppelkupplung (PDK) — 911 Carrera & 911 Targa 4 Models". Dr. Ing. h.c. F. Porsche AG.
49. Atlas, Steve. (8 October 2009). "2010 Honda VFR1200F First Look". Motorcycle USA.
50. "First double-clutch transmission in a truck".
51. "Honda's new 8-speed DCT uses a torque converter".