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
Audi was restructuring their model lineup in early and mid-1990s, and in late 1994, began selling the fifth generation (C4) Audi 100 model, re-badged as the Audi A6. Wanting to keep a sports-saloon in their lineup, the company made small revisions to what was previously known as the Audi S4, renaming it the Audi S6; the S4 name would eventually be re-used for a completely different model derived from Audi's smaller Volkswagen Group B platform-based Audi A4. As this was the first S6 model from Audi, it is commonly referred to as the "Ur-S6", derived from the German augmentive, "Ursprünglich" (meaning: original).