Starting from 1975, he was manager of technological engineering, being responsible for the concepts of the Audi 80 and Audi 100. He celebrated his 40th birthday on 17 April 1977 with a ball at which guests included Giorgetto Giugiaro and at which the staff of the Porsche Hotel presented him with an Audi 80 that was just 40 cm (16 in) long and constructed of marzipan.[6] In 1977 he also initiated the development of a car for the World Rally Championship, resulting in the four-wheel drive Audi Quattro. The engine used in the Quattro model was a turbocharged inline-5 cylinder unit.