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.
Quattro (four-wheel-drive system)
Starting with the B7 Audi RS4 and the manual transmission version of the 2006 B7 Audi S4. It was adopted in the entire S4, S6, and S8 lineup in 2007.