It used a turbocharged 2.1L five-cylinder, 200 HP, and a permanent all-wheel drive system with manually lockable centre and rear differentials.
Rally regulations at the time said nothing about AWD because nobody thought it was relevant.
Audi entered anyway, and won the World Rally Manufacturers' Championship in 1982 and 1984, and the Drivers' Championship in 1983 and 1984.
Only 400 cars were required for homologation.
Demand was high enough that Audi built 11,452 in total between 1980 and 1991.
Before the Quattro, all-wheel drive belonged to tractors and military vehicles and was a rare feature among sports cars.
After it, every performance car manufacturer in the world had to reconsider what a fast road car could be.