As Volkswagen and its group brands SEAT, Skoda and Audi reveal new concept and production designs at motor shows in the US, Europe and Asia, the availability of its dual-clutch transmissions is set to reach additional model lines as well as reach downwards to smaller vehicles and appear on more powerful Audi sedans and sports cars.

Volkswagen and Audi pioneered the introduction of dual clutch transmissions on road cars in 2003 with the six-speed DQ250 unit fitted to the Golf R32 and Audi TT sports car. Some 311,000 light vehicles were produced in Western Europe with dual-clutch transmissions in 2008, according to data from JD Power; of these, the overwhelming majority were Volkswagen-group models.  CSM Worldwide puts the likely 2009 DCT share of Western European vehicle production at 3.47 percent, set to rise to over 12 percent by 2015 as other automakers volume DCT programs become more prevalent.

The application of DCT technology to the new super-economical 1.2 liter Polo BlueMotion, the attractive BlueSport roadster, and the most powerful six-cylinder diesels from Audi shows how the system is able to combine fuel saving with performance and driver enjoyment. Additional applications within the Skoda and SEAT ranges show how focusing on DCT can appeal to the value-conscious buyer too.

Perhaps the most convincing demonstration of the potential of diesel and DCT to combine economy and excitement is seen in the shape of Volkswagen’s BlueSport concept, a two-seater roadster previewed at the Detroit show. Equipped with VW’s two-liter TDI diesel set transversely behind the two occupants and driving the rear wheels through the company’s familiar six-speed DSG dual wet clutch transmission, the 178 hp machine promises a top speed of 226 km/h (140 mph) and 0-100 km/h (0-62 mph) acceleration in 6.6 seconds. Most remarkably, however, the light 1200 kg roadster is expected to emit just 113 grams per kilometer of CO2, corresponding to diesel consumption of 4.3 liters per 100 km (52.6 US mpg).

Volkswagen engineers say the base engine for a production version of the BlueSport roadster could be the 1.4 liter turbocharged gasoline unit; this would likely be linked to the group’s seven-speed dry-clutch DCT, which has a torque limit of 250 Nm.

That same transmission is a core feature of a further VW concept: a new 1.2 liter three-cylinder TDI version of the new Polo BlueMotion. The standard Polo BlueMotion is a 1.6 liter four-cylinder with 90 hp and emitting 96 grams of CO2 per kilometer; the Concept version, which VW expects to put on sale in spring 2010, has 75 hp and just 87 g/km CO2, making it the most economical five-seater car in the world.

Volkswagen says that a stop-start system, which links very effectively with the DSG transmission, saves 0.2 liters of diesel per 100 km, while aerodynamic improvements cut a further 20 percent. Sister brand SEAT’s Ibiza, a small car built on the same platform as the Polo, also offers the seven-speed dry-clutch transmission, with the higher-torque wet-clutch six-speed doing duty on larger models such as the Leon and Toledo. At Skoda the Golf-sized Octavia offers both the seven- and the six-speed, depending on the engine choice, as does the larger Superb model.

Yet it is premium brand Audi that has embraced dual-clutch technology with the greatest enthusiasm, with three different transmission systems. The group’s seven-speed dry-clutch unit takes care of lower-torque transverse applications, typically small gasoline engines such as the 1.4 liter turbo and supercharged four-cylinder in the A3 hatchback. The wet-clutch six-speed – soon due for an upgrade as it was the group’s original DCT in 2003 – has a higher torque capacity and is again configured for transverse engine installations such as the TT sports car.

Audi’s major step forward has been to develop a bigger DCT suitable for the longitudinal engine configuration of its larger models – the A4, A5, Q5 and the next-generation A6 and associated models. With twin wet clutches and a torque capacity of 600 Nm this transmission does more than just allow use with powerful diesel engines: it also brings DCT into the premium segment and is compatible with Audi’s signature all-wheel drive (AWD). In so doing, it provides Audi customers with a remarkable range of transmission choices: five and six-speed manuals, mainly on smaller cars;  six- and seven-speed S tronic DCTs across the range, including most quattro models; the Multitronic CVT, on front-drive versions of the A4, A5 and A6;  and the six-speed Tiptronic torque converter planetary automatic on high-torque applications, including quattro. One oddball transmission is the R tronic sequential AMT on the mid-engined R8 supercar, presented as an alternative to the standard six-speed manual.

For an analysis of the new seven-speed longitudinal DCT, click Inside Audi’s premium DCT.

Story Filed: 5/8/2009
By Tony Lewin, managing editor DCTfacts.com