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 S4
The S4 along with the other B8 models received a facelift in early 2012. This included a revised front-end with new headlights and grille, an updated interior, and upgraded MMI options. Mechanically, the facelift B8 (known colloquially as the B8.5) was upgraded with electromagnetic steering and a lighter crown gear center differential.