Audi AG will expand its S-tronic dual-clutch transmission offerings later this year with the launch of a new 7-speed unit designed for higher-power, longitudinally mounted engines.

Until now, the auto maker’s BorgWarner Inc.-sourced DCT gearboxes have been shared with Volkswagen AG, which introduced the technology in 2002.

Branded Direct Shift Gearbox (DSG) by VW and S-tronic by Audi, the automated transmissions have brought better fuel economy and driving dynamics to several small vehicles with horizontally mounted 4- and 6-cyl. engines, including the VW GTI, GLI and Eos convertible, as well as the Audi TT and A3.

In contrast, the new 7-speed DCT was developed with BorgWarner solely for Audi, the auto maker says, and will be rolled out in several mid-range and sporty models throughout the year.

The 7-speed S-tronic shares the same quick shifting and all-wheel-drive compatibility as existing DSG units, but is differentiated by its robust 406-lb.-ft. (550 Nm) of torque threshold and ability to be joined with more powerful engines with north-south placements. Engine speeds up to 9,000 rpm also can be tolerated.

Audi is coy about applications for the new transmission, but its higher torque rating means theoretically it could withstand the punishment doled out by the 420-hp R8 sports car and RS4 sport sedan, both of which produce only 317 lb.-ft. (430 Nm) of twist from their 4.2L FSI V-8s.

Reports hint one of the first uses for the 7-speed S-tronic may be in the all-new Q5 cross/utility vehicle in Europe.

However, Michael Dick, Audi’s head of worldwide research and development, recently told Ward’s the all-new S4 sedan expected later this year initially will feature a DCT in the European market.

U.S. availability is uncertain, but the current ’08 S4 sedan produces 340 hp and 302 lb.-ft. (409 Nm) of torque from a 4.2L V-8.

Other possibilities include future variants of the A5/S5 lineup, as well as the A3, which is expected to be redesigned later this year.

Similar to all DCTs, the new S-tronic has odd-numbered gears arranged on one input shaft and clutch, with even gears and reverse positioned on another, concentric shaft/clutch. Operation is by steering wheel-mounted paddles or by the console shifter, with drive, sport and manual modes.

Power flows through a locking center differential in the quattro AWD system with a default 60% rear-drive bias. When traction is limited, the bias can be upped to 85% in the rear, or 65% up front, Audi says.

Other notables include triple-cone, carbon-coated synchronizers in the lower gears and reverse, along with dual oil systems – one for the wet dual-clutch assembly, mechatronic-control module and pump, the other for the wheelsets and center and front differentials.

Audi says this separation allows for the ideal placement of components without compromising lubrication.

msutton@wardsauto.com