After exiting the Tertre Rouge corner, cars spent almost half of the lap at full throttle, before braking for Mulsanne Corner. The Porsche 917 "long tail", used from 1969 to 1971, had reached . After engine size was limited, the top speed dropped until powerful turbo engines were allowed, like in the 1978 Porsche 935, which was clocked at . Speeds on the straight by the Group C prototypes reached over during the late 1980s. At the beginning of the 1988 24 Hours of Le Mans race, Roger Dorchy driving for Welter Racing in a "Project 400" car, which sacrificed reliability for speed, was clocked by radar travelling at . Jean-Louis Lafosse and Jo Gartner would ultimately suffer from fatal high speed accidents in 1981 and 1986, respectively, leading to concerns with the growing speeds on the 3.7 mile straight.