40 years, 40 figures, 40 images: fascinating facts and tales about Audi’s quattro technology

Around 720 PS (530 kW) is what the five-liter turbo in the Audi 90 quattro produced, which competed in the IMSA GTO series in 1989 – the 2.2-liter four-valve powerplant summoned no less than 329 PS from every liter (0.04 cu ft) of displacement. The drivers, Hurley Haywood and Hans-Joachim Stuck, won almost every second race in the North American series. Audi exploited the technical rules of the IMSA series to the full: A tubular trellis frame supported a greatly widened plastic body, while the tires were up to 360 millimeters (14.2 in) wide.