Audi A6
Audi made a high-performance, 4.2-litre V8 engine (parts code prefix: 077, identification code: AEC) with a Bosch KE-Motronic ECU available as an option in the original European S4s, and made the decision to continue to do so with the S6, making a version of the 4.2 available as an optional upgrade over the 2.2-litre inline five-cylinder turbo. Unlike the five-cylinder turbocharged version, the V8-powered S6 was supplied with a four-speed automatic transmission as standard, but kept the quattro four wheel drive. A six-speed manual gearbox was also available as an option.
Audi Sport GmbH
quattro GmbH has historically only been able to produce one specific model at a time at its sole plant at Neckarsulm. Chronologically, the first quattro GmbH model produced was the Audi RS2 Avant, a joint venture between Porsche and quattro GmbH, from 1994-1996 (and actually built at Porsche's Zuffenhausen plant). After this initial joint venture, all subsequent cars have been solely (with the exception of the Audi TT RS) produced at Neckarsulm by quattro GmbH. The second car was the C4 S6 Plus, produced from April 1996 to July 1997. Third was the 2000-2001 B5 RS4 Avant quattro; fourth was the 2003 C5 RS6 quattro; fifth was the 2005 B7 A4 DTM Edition saloon. Sixth out of quattro GmbH was the 2006 B7 RS4 quattro, seventh out of quattro GmbH was the 2006 B7 S4 25 Quattro, the eighth was a special edition A4 S-Line with and additional options for local markets - for example the UK 'Special Edition' with black optics pack, ventilated cross-drilled front disc brakes, black exhaust pipes, two tone leather interior - and the Swedish 'TS' designation with ventilated cross-drilled front disc brakes, S4 chassis, sport seats and aluminum interior detailing, and as of 2009, the ninth and latest offering is the 2008 C6 RS6 5.0 TFSI quattro.