1975, he was manager of technological engineering, being responsible for the concepts of many Audi models from the 1970s and 1980s, including the Audi 80, Audi 100 and the Audi V8. 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 long and constructed of marzipan. 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. Piëch held a small engineering company in the time between leaving Porsche AG and joining Audi, and while there, he developed a 5-cylinder in-line diesel engine for Mercedes-Benz. He picked up the concept again after moving to Audi, because there was a market demand for engines with more than 4 cylinders. At the time, Audi (and the Audi-derived VW Passat/Santana model range) used longitudinally mounted inline engines and front wheel drive. More conservative layouts with 6 cylinders were rejected because of engineering and production costs (V6 engine) or packaging requirements (straight 6 did not fit because front wheel drive required that it be mounted in front of the axle). In 1993, Piëch moved to Volkswagen AG, parent company of the Volkswagen Group, where he became Chairman of the Board of Management, succeeding Carl Hahn. At that time Volkswagen was only three months from bankruptcy, and he was central to orchestrating its dramatic turnaround. He retired from the Board of Management in 2002, but still served in an advisory capacity as Chairman of the Supervisory Board. In 2000, he was named chairman of Scania AB. He retired from the management board in 2002 and was succeeded as chairman by Bernd Pischetsrieder. While head of Volkswagen Group, Piëch was known for his aggressive moves into other markets. He drove the Volkswagen and Audi brands upmarket with great success. Piëch also pursued other marques, successfully acquiring Lamborghini for Audi, and establishing Bugatti Automobiles SAS. His purchase of British Rolls-Royce and Bentley was more controversial. After successfully buying the Crewe, England, car building operation, including the vehicle designs, nameplates, administrative headquarters, production facilities, Spirit of Ecstasy and Rolls-Royce grille shape trademarks, VW was denied the use of the Rolls-Royce brand name, which had been licensed to BMW