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BMW M1/C | Secret History

The one-season IMSA wonder that spelled the end for BMW's Group C plans...

By Dafydd Wood / Monday, April 6, 2020

The competitive history of the BMW M1 is hardly a secret. One of motorsport's - let alone its manufacturer's - most revered models, the Procar championships of 1979 and 1980 remain the stuff of legend. Such a series seems almost impossible to contemplate today; a one-make grid supporting the F1 calendar on its European legs, with eight rounds (nine in 1980) at circuits like Zolder, Monaco, Silverstone and Imola.

Competitors were plucked from all types of racing, with the top five F1 drivers in practice on any given weekend automatically earning a place. Single-seater legend Niki Lauda was crowned champion in '79, the highlight of an otherwise difficult season which saw him retire from F1 for the first (though not the last) time. While in 1980 his shoes on the top step of the podium were filled by Nelson Piquet, who also finished a close second to Alan Jones in the F1 drivers' championship that year.

As entertaining as Procar had been, however, M1s struggled for success elsewhere. A win for Hans Joachim Stuck and Nelson Piquet at the 1981 Nurburgring 1,000km seemed promising, but even in beefed-up Group 4 and 5 guise, a lack of reliability across the board saw the M1 flounder. A total of 22 factory and privateer entries over eight years at Le Mans recorded a best finish of just sixth - at the first attempt - with 14 DNFs. Across the pond, though, things were about to look up.

In America, the M1 Procar had competed rather unsuccessfully in the 1980 IMSA Camel GT series. Finding itself stuck in the series-topping experimental GTX class - rather than the more appropriate GTO class due to a lack of homologation - the 480hp produced by the M1's 3.5-litre inline-six was no match for the 600hp of rivals like Porsche's 935, a situation not helped by the M1's considerably heavier mass.

A switch to GTO for the 1981 season, however, made all the difference, the M1 winning all but four rounds of the championship and dominating its class like few cars before or since. Curiously, however, while BMW's mid-engined flagship finally seemed to have found success in the lower class, another M1 continued to struggle at the front of the grid.

Dubbed the M1/C, it was powered by the same six-cylinder, 3.5-litre motor as the GTO M1, producing the same 480hp. It, however, raced in an all-new category for 1981: GTP. Unlike the GTX class it would eventually usurp, in which cars were still required to bear some resemblance to their road-going counterparts, GTP (for prototype) allowed much greater freedom. It was the perfect format, BMW thought, in which to develop a racer for the FIA's upcoming Group C series, set to begin in 1982.

The German marque turned to March Engineering to build the car, which based the design around the lightweight aluminium monocoque chassis of its own 81P. As well as the M1's engine, it made use of the car's brakes and suspension, yet thanks to its prototype design the finished machine weighed over 120kg less, at just 900kg. Piloted by David Hobbs and Marc Surer it finished sixth on its first outing at the Riverside Six Hours, finding itself at a disadvantage to the Porsche 935s, just as its less exotic sibling had done the season before.

Back in the M1's maiden 1980 IMSA season, and in a desperate attempt to make his car more competitive, frustrated privateer Jim Busby had resorted to swapping out the car's BMW straight-six for a 6.0-litre, 700hp Chevy small block. Now it was BMW's turn to try a similar trick; the F1-derived unit intended for the car still wasn't ready, so instead it turned the 2.0-litre turbocharged motor used in its Formula 2 racers to replace the standard powerplant.

So equipped the M1/C was also capable of producing up to 700hp; it was not, however, capable of handling it. The car was fast, taking a couple of pole positions, but a string of mechanical failures and DNFs followed before BMW pulled the plug on the project at the end of the season. Not only was the M1/C done in GTP, but the manufacturer never entered a factory effort in Group C, either.

That wasn't entirely the end of the M1/C story, though. A descendant of the car, the March 83G - re-designed by a young man by the name of Adrian Newey - would go on to win the IMSA GTP championship just two years later. Its engine? The turbocharged flat-six from a Porsche 935. BMW would return to IMSA with another March-built car in 1986, the 86G-based GTP. Despite making use of the same BMW M12/13 engine as the Brabham F1 team's BT55, though - a unit capable of up to 1,400hp in qualifying and 811hp in race trim respectively - it too found success hard to come by. Luckily for BMW, its best F1-powered prototype racer was yet to come.

Photo credit | BMW USA

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