The Audi S4 was first introduced as a performance variant of the Audi 100, yet the name has become most well known as the performance version of the Audi A4. The first A4-based S4 was introduced for the 1998 model year, and was offered as a sedan or 'Avant' station wagon, and with manual or automatic transmissions. The four main B5 S4 variants were: Sedan - Manual, Sedan - Automatic, Avant - Manual, and Avant - Automatic. These cars were powered by a 2.7L twin turbo V6 engine, and featured numerous improvements to the drivetrain, chassis, and exterior over the standard A4. Production of the B5 generation of Audi S4 ended in 2002, but the model series continued in the next A4 generation as the B6 Audi S4.