Audi S4
Audi's quattro four-wheel-drive system was standard on the C4 S4/S6; a first-generation Torsen-based system which used the "T-1" automatically biasing centre differential (ATB) was used on vehicles equipped with manual transmissions, while a transfer box based system was used on vehicles equipped with an automatic transmission.
Audi S6
The Audi S6 and S7 are powered by a 4.0L DOHC twin-turbo V8 engine mated to a 7-speed S-tronic Double Clutch Gearbox. This engine makes and of torque, plus there is a cylinder-deactivation system and a stop-start system for improved fuel economy. The 2013 Audi A8 shares the same engine, while the 2012 Audi S8 has a variant of the powerplant in a higher state of tune making and of torque, both mated to an 8-speed automatic transmission.