The most powerful and notable variant of the Audi Quattro was the Sport Quattro. Two variants of the Sport Quattro were produced, the S1 and the S1 E2. The Sport Quattros were created in order to meet homologation rules for the Group B Rally Championship, and not only featured more powerful engines, but were also created on a shortened platform to give the car improved agility. The rarest and most desired of all Quattro variants, the Sport Quattro cars were fitted with advanced turbocharged engines which produced nearly 500hp. Due to the motorsport success of the Audi Quattro, these Sport variants have become some of the most desirable and sought after Audi cars. Production of the Audi Sport Quattro ended in 1986.