BMW M1 Group 5

Group 5 was the "silhouette" category, so called, Alan Henry explained in Motor Sport, because one of its few rules was that a racing car had to keep the outline of the road car it came from. Roger Bell put it more bluntly: "For silhouette read anything goes, so long as the racer retained the outline and layout of the qualifying homologation specials." Bell wrote that BMW had conceived the M1 to beat Porsche's turbocharged cars in that class. But a Group 5 car had to be derived from one already recognised in Groups 1 to 4, and the M1's Group 4 recognition came only from 1 December 1980, so until then BMW's Group 5 car raced in IMSA's classes, at Le Mans and in the United States. Adam Cooper's summary in 2008 was that "a Group 5 version – which owed little to the original – was also seen".⁠source 5​source 6​source 7​source 8​source 9

BMW's own Group 5 car was planned from the start, and Motor Sport reported the plan in January 1979:

Stuck was to be its first driver and Le Mans 1980 its "ultimate aim". The car that raced had the normally aspirated M88, and no turbocharged March M1 appears in any result read. racingsportscars records a "BMW March M1" as a reserve entry at Le Mans in June 1979. In February 1980 two March-BMW M1s started the Daytona 24 Hours, one entered by March Engineering and one by Jim Busby, and both stopped with broken drive shafts. Busby's car ran again at Sebring in March, where its gearbox (transmission) failed, and at Riverside in April, recorded there with a Chevrolet engine. At Le Mans in June 1980 March Engines entered No. 82 for a crew that included Manfred Winkelhock, and it went out after an accident on lap 38.

The Le Mans records give its chassis as 002 in 1979 and 002a in 1980, and with two cars at Daytona there were at least two. How many March built, no source read says. March's next car for BMW North America, the M1/C of 1981, was a March of its own design, and the M1 race car follows it.⁠source 3​source 1​source 10

Schnitzer built the M1 that came nearest to BMW's turbocharged plan, and raced it in the German championship's first division in 1981, entered at first as the Lubrifilm Schnitzer BMW Team. touringcarracing calls it the only new challenger of that season, and sums it up:

touringcarracing gives its specification: a BMW straight six with a smaller bore than the road engine's and the same stroke, 3,150 cc in all, with two overhead camshafts, four valves per cylinder and two KKK turbochargers; a Hewland or ZF four-speed gearbox; wheels of 13 × 16 inches in front and 15 × 19 at the rear; and a weight of 1,065 kg (2,348 lb). BMW described Schnitzer's car in 2008 as having "a kevlar body".

The power is a matter of whose figure. No source read gives one figure for "the Group 5 M1", and each claim below belongs to its own car and kind:

Stuck drove it, as No. 51, in a season short of money:

It retired at Zolder in March, at Hockenheim in April, at Mainz-Finthen in May and at the Nürburgring Supersprint in September. At Wunstorf it was scratched because its sponsor, Lubrifilm, had refused to pay the bills. A week later, at the Norisring, Wollek's Porsche ran out of fuel 3 laps from the end while Stuck, unsure of his own fuel, kept going, and touringcarracing recorded the mood: "the team was ecstatic; a fine revenge to sponsor Lubrifilm, who had stopped paying weeks ago and whose decals were removed from the car." At the Salzburgring Stuck took pole and fastest lap and won in the rain, the gearbox stuck in fifth late in the race. At Hockenheim only Manfred Winkelhock's Capri beat him.

Schnitzer ran a second M1 in 1981, serial 4301072, a former Procar, which was seventh at the Norisring; whether it was a turbo, no source read records. Nor does any source read say whether the Schnitzer M1 that Stuck drove to four wins in German races in 1982 was the same turbo car.⁠source 4​source 11​source 12​source 3​source 6​source 7​source 13​source 14

Sauber built two space-frame Group 5 M1s, which racingsportscars records as 81.M1R.01 and 81.M1R.02. They kept the normally aspirated six of the Procar, with Kugelfischer injection and a ZF five-speed gearbox, ran on Dunlop tyres and, by Slickpix's account, had aramid (Kevlar) bodies.

81.M1R.02 was GS-Sport's car in BASF colours. At the Nürburgring on 24 May 1981 Stuck and Piquet led when the race was stopped after 17 of its 44 laps. Stuck remembered the car and the day in 2011:

The rest of its season was harder. At Le Mans, with Jarier, Stuck and Helmut Henzler, it went out after 57 laps with accident damage, and at the Brands Hatch 1000 km Stuck and Heyer crashed out. In the German championship GS-Sport entered it for Piquet at the Norisring, where he did not start the championship race, and for Christian Danner, who was sixth at Hockenheim and third at Zolder; only the Zolder entry carries the chassis number. In the Kyalami 9 Hours on 7 November 1981 Stuck crashed at night: "I hit the wall at 250kph … The car broke in half," he told Motor Sport in 2011.

81.M1R.01 was Sauber's own, in the colours of Würth and Lubrifilm. Marc Surer and Dieter Quester were 13th with it at the Nürburgring in May, and at Le Mans its engine failed after 207 laps. It raced on for others: BMW Italia were third with it in the Nürburgring 1000 km of 1982, and Enzo Calderari won a Swiss championship race at Dijon in April 1982 and, with Marco Vanoli, the Hockenheim 3 Hours on 29 October 1983. The car on this page's cover is in that car's Le Mans livery of 1981.⁠source 1​source 12​source 4​source 15​source 13

Procars ran under Group 5 rules too, as entries more than as new cars. EMKA's car, 4301028, which Niki Lauda had raced in Procar, ran in Group 5 at Le Mans in 1981 and won the class for cars over 2 litres at the Brands Hatch 1000 km that year. BMW Italie-France's No. 51 was fifth in Group 5 at Le Mans in 1981, Total's 4301059 third in the class at Le Mans in 1982, and BMW Motorsport entered 4301269 as an "M1 Gr.5" at Mosport in 1981, where it was 14th. The Register marks all three serials PROCAR.⁠source 1​source 16