The Audi Sport Quattro S1 was the full Group B competition evolution of the road-homologation Sport Quattro, developed to contest the World Rally Championship against increasingly powerful rivals from Peugeot and Lancia. Built around the shortened wheelbase platform of the road car, it carried a heavily developed version of the turbocharged 2.1-litre five-cylinder engine tuned to outputs that climbed well beyond 400 horsepower in later specification, with the E2 variant representing the most extreme stage of that development. The S1 E2 in particular featured dramatic aerodynamic bodywork, including a prominent front splitter and a large rear wing, generating significant downforce and giving the car one of the most recognisable silhouettes of the Group B era. Its all-wheel drive system, which had defined the original Quattro's rally success earlier in the decade, remained central to the S1's technical identity even as the power figures pushed into territory that made the cars progressively harder to manage on stage.
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