The Audi Sport Quattro S1 E2 was introduced at the end of 1985 as an update to the Audi Sport Quattro S1. The car featured an inline five-cylinder engine that displaced 2,110 cc (128.8 cu in) from a bore and stroke of 79.5 mm × 85.0 mm (3.13 in × 3.35 in) and generated an officially quoted power output figure of 480 PS (353 kW; 473 hp). However, the turbocharger utilised a recirculating air system, with the aim of keeping the unit spinning at high rpm, when the driver closed the throttle, either to back off during cornering, or on gearshifts. This allowed the engine to resume full power immediately after the resumption of full throttle, reducing turbo lag. The actual power figure was in excess of 500 PS (368 kW; 493 hp) at 8,000 rpm.
The S1 E2 made its debut at the 1985 Rally Argentina, with Blomqvist driving. This variant was successful in the rally circuit, with Röhrl and Christian Geistdörfer winning the 1985 San Remo Rally. A modified version of the E2, was also driven by Michèle Mouton. The S1 E2 would become the final Group B car produced by Audi, with the works team withdrawing from the Championship following the 1986 rally in Portugal. The final factory cars of 1986 were rated at 600 PS (441 kW; 592 hp). In 1987, the car won the Pikes Peak International Hill Climb driven by Walter Röhrl.
History : See wikipedia article