The P82 was powered by a Garrett twin-turbocharged 2.7-litre Peugeot PRV V6 engine producing between 600 and 890 hp at 8,300 rpm depending on boost pressure, driving the rear wheels through a five-speed manual transmission. The chassis was built as an aluminium monocoque and the complete car weighed approximately 900 kg. Gérard Welter, who worked professionally as an aerodynamicist and vehicle designer at Peugeot, leveraged access to Peugeot's wind tunnel to refine the aerodynamic package — a significant advantage for a small privateer operation.
The best result achieved by the P82 itself was a sixth-place finish at the 1982 1000 km of Monza, driven by Roger Dorchy, Guy Fréquelin, and Jean-Daniel Raulet.
The P83 was developed for the 1983 season, intended specifically for the 24 Hours of Le Mans. The monocoque construction was retained and the bodywork was pulled down tightly over the rear wheels — a recognisable Welter styling trait. A powerful rear wing provided downforce on the rear axle. Power came from a 2.8-litre six-cylinder Peugeot turbo engine producing close to 420 hp.
Welter entered two cars at Le Mans in 1983. Both qualified poorly, finishing 17th and 18th in practice. Car number 9, driven by Belgian driver Didier Theys, retired after 102 laps when the Peugeot engine overheated and would not restart following a pit stop. Car number 10, shared by Pascal Fabre — who would drive for the AGS Formula One team in 1987 — and regular Welter driver Roger Dorchy, also struggled with overheating but eventually completed the race in 16th place overall.
For 1984 the cars were revised and designated P83B. The most visible change was a wider rear end, though the rear wheel covers were retained. The 1984 race produced the most dramatic moment in Welter's Le Mans history: Roger Dorchy, starting from eighth on the grid, briefly moved into the lead — the first time a Welter car had led at Le Mans. The lead lasted only one lap before Dorchy was passed, and ultimately both cars retired. In 1985 the number 42 car, shared by Dorchy and former Le Mans winner Jean Rondeau among others, finished 17th overall; a second car was disqualified and a third crashed.
The P83's final Le Mans outing came in 1986. Already superseded by the new P86, the car qualified in 34th position. The crew of Roger Dorchy, Claude Haldi, and Pascal Pessiot nevertheless brought the car home in twelfth place overall.
The P86 was constructed in 1986 as the definitive evolution of the lineage. The type designation followed the team's established logic: W for Gérard Welter, M for Michel Meunier, P for prototype, and 86 for the development year. Only one chassis was built.
Aerodynamically the P86 retained the fully enclosed rear wheel arches common to all Welter designs; during tyre changes the covers could be folded up to minimise pit-stop time. The 2.8-litre V6 turbo engine was upgraded to produce approximately 550 hp, and the unit fitted to the Welter cars was notable for being the only DOHC variant produced in the entire PRV engine family.
The P86 appeared at Le Mans twice. In 1986, Jean-Daniel Raulet, Michel Pignard, and François Migault drove car number 41 in the C1 class, but retired after 132 laps with engine failure. In 1987 the same car, now crewed by Raulet, Migault, and Pascal Pessiot, again failed to finish — again due to engine failure.
Welter Racing remained a small, technically ambitious operation throughout its Group C years. The series of cars demonstrated that a tight privateer team, backed by Peugeot engineering expertise and wind-tunnel access, could develop aerodynamically sophisticated machinery capable of leading at Le Mans, even if outright reliability remained elusive. The P83B's brief leadership in the 1984 race stands as the high point of the programme.