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.
Quattro (four-wheel-drive system)
The Torsen T3 centre differential combines a planetary gear set with a Torsen differential in a compact package developed for centre differential installations. Unlike the T2 Torsen where the torque split is a nominal 50:50, in the T3 Torsen the torque split, due to the use of the planetary gear set, is an actual asymmetric 40:60 front-rear torque split (i.e., when grip is equal on both front and rear axles, 40% of torque is sent to the front axle, and 60% to the rear). As with the T1 Torsen, torque will be distributed dynamically depending on tractive conditions, but with an actual (rather than nominal) static bias. The T3 allows handling characteristics and vehicle dynamics more akin to rear-wheel drive cars. This asymmetric Torsen was first introduced in the highly acclaimed 2006-model (B7) Audi RS4. The Type 3 torsen was used in the Audi S4 and RS4 B7 manual transmissions from 2006 to 2008, as well as the S6, S8, and Q7 models from 2007.