The Audi Sport Quattro S1 was introduced in 1985 as an update to the Audi Sport Quattro. The car featured a inline 5-cylinder engine that displaced 2110 cc and produced an extraordinary 560 bhp. In addition to the improved power output, an aggressive aerodynamic kit was added that featured very distinctive wings and spoilers to the front and rear of the car.
Twenty years after the cancellation of Group B, the Sport Quattro S1 was still widely regarded as the most powerful rally car ever fielded in international competition, with the final factory machines of 1986 rated at 600bhp.