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 RS 4
The B7 RS4 was planned to replace the C5 RS6 in the SCCA Speed World Challenge, but after Champion Racing had prepared the car, it was decided not to compete in the series, due to rule changes imposed by the Sports Car Club of America (SCCA) on Audi concerning 4WD systems, wheels size, and engine power output. Rather than scrapping the fully built Speed World Challenge RS4, Champion and Audi used the car as a part of the American Le Mans Series Vitesse Program, which highlights the technology link between race cars and conventional series production road cars.