The Audi S4 is the high performance variant of Audi's compact executive car A4. The original Audi S4, built from 1991 until 1994, was a performance-oriented version of Audi's 100 saloon/sedan. All subsequent S4s since 1997 have been based on the Audi A4; and as the A4 has evolved from one generation to the next, so has the S4. A more powerful internal combustion engine, larger upgraded brakes, firmer suspension, larger roadwheels, and distinctive sheetmetal, styling clues and badging have always been amongst the many upgrades the S4 receives over its mainstream 100 and A4 siblings. In markets where the even higher-performance Audi RS4 is not offered, the S4 is the top-of-the-line trim of the A4 family. Like its regular A4 counterpart, all S4 variants have had longitudinally oriented, front-mounted engines. A single turbocharged 2.2 litre inline five-cylinder powered the original C4 version, and a 2.7 litre twin turbocharged V6 engine was found in the B5 generation.
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