Audi Ur-S4 / Ur-S6
The Ur-S4 was produced from 1991 to 1994, while the Ur-S6 was produced from 1995 to 1997. They both featured a 2.2 litre, 5-cylinder engine with turbocharging and an intercooler, with of torque. In Europe, V8-powered versions of both S4 and S6 were available. The S4 version sported a engine (the same "ABH" engine as in Audi V8), the S6 had an upgraded engine "AEC" with . American versions featured a 5-speed manual transmission and in Europe a 6-speed, as well as a 4-speed automatic transmission could be substituted.
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.