In late 1997, Audi introduced an all-new range of Audi A6 models, based on the Volkswagen Group C5 platform. A new Audi S6, now officially known as the Audi S6 quattro appeared in 1999, to complement its A6 platform-mate. It was available in a four-door saloon/sedan and a five-door Avant (estate/wagon). In North America, the Avant bodystyle was the only version available. The vehicle could accelerate from standstill to 100 kilometres per hour (62.1 mph) in 5.7 seconds, and from 0 to 200 km/h (124.3 mph) in just 21.7 seconds. The top speed was electronically governed to 250 km/h (155.3 mph).
Motive power is from a new rubber-hydro mounted all-aluminium alloy 4.2 litre 40-valve (five valves per cylinder) 90° V8 petrol engine, with twin double overhead camshafts and solenoid-operated magnesium two-stage variable intake manifold. It displaced 4,172 cubic centimetres (254.6 cu in), and was rated at 250 kilowatts (340 PS; 335 bhp) at 6,600 revolutions per minute (rpm), producing 420 newton metres (310 ft·lbf) of torque at 3,400 rpm. It satisfied the European Union EU3 emissions standard, and engine management was by way of a Bosch Motronic ME 7.0 electronic engine control unit (ECU), with manifold-sited sequential fuel injection, mapped direct ignition with eight individual spark coils, Bosch longlife spark plugs, four heated lambda sensors and two catalytic converters, cylinder-selective knock control, and a Bosch "E-Gas" drive by wire throttle. The engine was now cooled with the aid of two electric cooling fans, replacing the single viscous fan of earlier models.
Source: Wikipedia, 2011