Check out an elderly Audi saloon capable of 420 km/h

Cars & Bids has just accepted a U.S. $33,000 top bid for an Audi S4 sedan converted into a time attack machine. It set a sedan speed record at the Bonneville Salt Flats 13 years ago by hitting 420 km/h (261 mph).

The car was manufactured in the 1990s and was originally known as the Audi 100 (C4). Later rebranded as the S4, it retained its understated, sleeper appearance while upgrading to a serious sports car powertrain. Buyers could choose between a 2.3-liter turbocharged V5 rated at 230 PS (227 hp / 169 kW) and a 4.2-liter naturally aspirated V8 capable of 280 PS (276 hp / 206 kW). Both came equipped with a Torsen interaxle differential and quattro AWD.

The example seen here is based on the turbo version and comes from Missouri-based Audi specialist Four Ring Performance. The entire drivetrain was overhauled with a massive BorgWarner S400SX turbocharger at its base and a custom air intake, resulting in 1,171 PS (1,155 hp / 861 kW) and 957 Nm (706 lb-ft) of torque. The most spectacular part is that both figures were measured at an actual dyno stand at the wheels, so the output at the crank should be even wilder than this.

Racing at the annual Bonneville Speed Week in 2012, the insane S4 managed to hit the 420 km/h (261 mph) mentioned above and maintain an average acceleration of 383 km/h (238 mph), something not a single sedan could accomplish before. It was driven by Jeff Gerner, the leader of Four Ring Performance at the time.

Among other things, the S4 was upgraded with a roll cage, a fire extinguisher, a brake parachute and wheels with aerodynamic “moon discs” for the race. Whoever bought it will have an opportunity to race it again, since it is still apparently in good condition.