Audi S4
Audi's quattro four-wheel-drive system was standard on the C4 S4/S6; a first-generation Torsen-based system which used the "T-1" automatically biasing centre differential (ATB) was used on vehicles equipped with manual transmissions, while a transfer box based system was used on vehicles equipped with an automatic transmission.
Audi S4
The powertrain details of the B5 S4 feature a 2.7-litre twin-turbo ('biturbo') 90° third-generation V6 engine (parts code prefix: 078, identification codes: AGB, AZB, APB). Details of the powerplant include a cast iron cylinder block with two lightweight aluminium alloy cylinder heads. The valvetrain includes 30 valves (five valves per cylinder), twin hybrid-driven (timing belt and roller chain) double overhead camshafts and variable valve timing for the inlet valves. The intake air is pressurized by two parallel water-cooled BorgWarner K03-series turbochargers; the charged air is cooled by two side-mounted air-to-air intercoolers (SMICs). It displaces , and is rated to produce a motive power output of at 5,800 rpm, and generates of torque at 1,850 rpm. Engine management was by way of a Bosch Motronic ME 7.1 (7.0 in North America) electronic engine control unit (ECU), and helped it meet the European EU-3D emissions standard. In all US-market cars, the engine was detuned to meet US emissions regulations; output was reduced to and (identification code: APB).