under the Audi S5 nameplate. C4 (Typ 4A, 1991–1994) Factory production of the original Audi S4 (Typ 4A), usually known as Audi 100 S4, began in August 1991 to serve as the performance version of the newly updated C4 platform 100 four-door, five-seat saloon. It was designed to replace the outgoing C3 based Audi 200 quattro turbo, which had been Audi's first true sports-saloon and had been discontinued at the end of 1990. Being the first S4 model from Audi, it is commonly referred to as the Ur-S4, derived from the augmentive word (meaning: original). Audi mildly updated the C4-based model line in 1994 and dropped the 100 nomenclature; all variants of the former Audi 100 line were now re-badged as the Audi A6. In line with the switch in model name, Audi temporarily discontinued the use of the S4 name and began selling an updated but fundamentally identical version of the car, based on the "new" A6 and badged as S6. Despite the change in name, differences between the outgoing S4 and incoming S6 were primarily cosmetic. A more powerful, more expensive and more exclusive variant known first as the S4 Plus and later as the S6 Plus was available from October 1992 through to July 1994. Built in very small numbers, the "Plus" models featured numerous performance enhancing upgrades; including the use of Audi's 4.2-litre V8 engine in place of the then current inline-five engine. An all-new C5-based Audi A6 debuted for 1997, after which the S4 and S6 became distinctly separate models based on very different platforms. The C4 variant S4 ended factory production after less than three years in July 1994. One of its most renowned owners was Ayrton Senna who owned a silver Avant, not least because he was the Audi distributor for Brazil. C4 powertrain In standard form, the powertrain detail of the C4-based S4 was available with only one engine, a single turbocharged and intercooled version of Audi's 2.2-litre 20-valve inline five-cylinder engine This displaced and was equipped with an advanced Bosch Motronic electronic engine control unit (ECU). This engine (parts code prefix: 034, identification code: AAN), developed a motive power output of at 5,900 revolutions per minute (rpm) and of torque 1,950 rpm. This powerplant made it rather powerful by contemporary standards, and the vehicle with five-speed manual transmission was able to accelerate from standstill to in 6.2 seconds. Both five- and