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 current generation S4 is powered by a 3.0L V6 with petrol direct injection and a single turbo EA839 engine. The engine uses an HSI (Hot Side In) layout, which places the cylinder head exhaust ports, exhaust manifolds, and turbocharger inside the V of the engine; this is a similar arrangement to the twin-turbo V8 engines used in Audi's S6 and S7.