Guide: Group 4 Dreaming - a Historical & Technical Appraisal of the BMW E26 M1 Procar (1978-1980)
BACKGROUND
BMW conceived the M1 supercar project to complement its existing Formula 2 engine supply deal and Group 5 Division 2 E21 320i programme. With a turbocharged iteration of M1’s 3.5-litre straight six expected to develop in excess of 850bhp, BMW hoped their new flagship model would to be able to topple Porsche’s 935 as the premier Division 1 Group 5 machine.
To qualify for the Group 5 Special Production Class, a manufacturer first had to have a base car homologated into either Group 1, 2, 3 or 4. BMW opted to create a Group 4 version of the M1 which necessitated a minimum 400 car production run within a 24 month timeframe. The Group 4 M1 was expected to supersede Porsche’s ageing 934 as the best car in its class.
Originally, BMW anticipated the M1 would be homologated in time to contest the 1979 season. However, continual delays (the contract with M1 production partner Lamborghini was cancelled in May 1978) meant it quickly became apparent that homologation would not be approved in time for the original deadline.
With the M1 road car scheduled to make its international motor show debut at the Paris Salon in October 1978, BMW was forced to come up with another way to publicise its expensive new range topper instead of a conventional international race programme. Although the German governing body had confirmed it would allow the Group 4 M1 to race in Group 5 un-homologated, this would hardly bring the worldwide exposure that BMW desired.
The inspiration for a leftfield solution came from BMW Motorsport boss, Jochen Neerspach, who managed to cut a deal with the Formula One Constructors Association (FOCA) to run Group 4 M1s in a one-make series that supported most of the Formula 1 races in Europe during the 1979 season.
Dubbed the Procar Championship, around 20 identical Group 4 M1s priced at 150,000 DM each (around $60,000 or £40,000) would contest an eight-race series with the first five grid slots at each round allocated to the quickest five drivers from F1 first practice. The other starting positions would be determined by qualifying times.
The M1 Procar championship was announced at a press conference at Hockenheim in July 1978 where a prototype and wing-less Group 4-style M1 was shown alongside a pre-production road car. At this stage, BMW still hoped to have the M1 homologated mid way through 1979 which would allow them to run a works Group 5 version during the second half of the season.
In October 1978, BMW confirmed Project Four in England and Osella in Italy would assist with the production of customer versions of the Group 4 M1 Procar.
The first true M1 Procar prototype was completed on December 5th 1978. Testing and development continued from winter into spring, but the M1 didn’t appear in its final Group 4 trim until April 29th when a works car was entered for a race-test at the DRM Nurburgring event where BMW Junior driver Marc Surer (who won the weekend’s F2 contest driving a BMW-powered March) qualified seventh. Having run sixth for the first half of the race, Surer began to drop back at half-distance with a sick engine and eventually finished ninth.
CHASSIS
Compared to the more extensive list of modifications permitted in Group 5, Group 4 regulations allowed relatively few upgrades over the base car. Wider wheels and tyres were OK in addition to lightly modified suspension and brakes. Some relatively minor aero upgrades were also permitted along with tuned engines and the installation of all the essential safety gear required for racing.
Each Procar started life as a standard M1 square section steel-tube spaceframe to which a beefy steel roll cage was added. Instead of the normal fuel cells (located on both sides ahead of the rear axle), new flexible ATL bag tanks were adopted.
As usual, unequal length wishbones, coil springs and gas-filled Bilstein dampers were fitted to each corner along with an anti-roll bar at either end. However, Procars were uprated with custom springs and adjustable dampers, uniball joints instead of rubber bushes and thicker, fully adjustable anti-roll bars.
There was also a new ATE brake system with bigger 332mm vented discs (up from 300mm front and 297mm rear). Floating calipers were installed, the servo-assistance was ditched and a cockpit adjustable balance arrangement fitted. A new hydraulic handbrake system was also plumbed in.
Reinforced centre-locking wheel hubs were another new Procar feature. The BBS wheels retained a 16-inch diameter, but went from 7 to 11-inches wide at the front and from 8 to 12.5-inches wide at the rear.
Goodyear tyres were originally used and the Procar also came with a quicker steering rack.
ENGINE / TRANSMISSION
Instead of the standard M88 24-valve dual overhead cam straight six used by the M1 road car, the Procar came equipped with an M88/1 unit that featured a host of upgrades.
Whereas the standard M88 lump was based around a cast-iron block with light aluminium alloy head, the M88/1 utilised an aluminium alloy block as well. It also incorporated a revised dry-sump lubrication system, forged pistons, hotter camshafts, bigger valves, guillotine-type throttle slides (instead of individual butterflies), a straight-through exhaust and ran a higher compression ratio (11.2:1 as opposed to 9.0:1).
Thanks to larger cylinder bores (94mm instead of 93.4mm), displacement went from 3453cc to 3498cc. Stroke was kept at 84mm.
A Kugelfischer mechanical fuel-injection system was retained.
Peak output went from 277bhp at 6500rpm to 470bhp at 9000rpm and 239lb-ft at 5000rpm to 288lb-ft at 7000rpm.
The existing five-speed ZF DS25 gearbox now came with a separate oil cooler, as did the new high-lock limited-slip differential. An uprated Fichtel & Sachs clutch was also fitted.
BODYWORK
Whereas Group 5 allowed manufacturers to substantially modify a base car’s appearance either side of the cockpit bulkheads, Group 4 was comparatively restrictive.
The M1 Procar came with a deep wraparound front apron that featured a gaping rectangular radiator intake and two circular brake cooling ducts as well as a jutting chin spoiler.
Down each flank, massive wheelarch extensions were necessary to cover the wider wheels and tyres. The side and rear windows were switched from conventional glass to lightweight Plexiglas. Quick fuel fillers were mounted on the sail panels.
At the rear was a high-rise rear wing with adjustable flap. The single pipe megaphone exhaust exited just off-centre as opposed to through the left-hand side of the rear apron.
Like the M1 road car, body panels were fashioned almost exclusively from fibreglass and bonded to the chassis.
INTERIOR
Inside, each M1 Procar was bereft of soundproofing and any superfluous upholstery. Only the bucket seat came trimmed (in fire-retardant fabric). A passenger seat was an optional extra. Four-point harnesses were used instead of regular safety belts.
The road car dash covered in soft-touch vinyl was carried over, but mated to a Procar-specific binnacle of much-reduced size. Housed centrally within this was a large rev counter flanked by four smaller read outs for oil pressure, oil temperature, water temperature and road speed. Located in between were a variety of warning lights.
A plain centre console replaced the original where controls for the ventilation and audio systems normally resided. Further back, the transmission tunnel was also simplified and now featured an array of basic switches along with a battery cut-off toggle.
Basic door trim housed wind-down as opposed to electric window switches.
WEIGHT / PERFORMANCE
As a consequence of the radical weight-saving measures carried out, each Procar tipped the scales at 1020kg which represented a 280kg reduction over the M1 road car. However, those examples that went on to race in Group 4 events outside of the Procar series often came in even lighter trim (often well under the 1000kg mark).
Depending on the gear ratios installed, a top speed of 193mph was possible (up from 163mph) while the 0-62mph time dropped from 5.5 to as little as 4.3 seconds.
PRODUCTION
M1 Procars were variously completed by BMW Motorsport in Germany, Project Four Racing in the UK and Osella Squarda Corse in Italy. The Procars assembled for customers by Project Four and Osella arrived in the early stages of completion direct from Ital Design who themselves received the bare chassis from Marchesi and bodies from Trasformazione Italiana Resina (both of whom were were based in Modena).
In total, 54 examples of the Group 4 M1 Procar were built.
PRODUCTION CHANGES
Production changes during the M1 Procar’s life were limited.
Following some unrest at the pace of the works cars at Dijon in late June (round three of the 1979 Procar Championship), rev limiters were raised from 8500rpm to 9200rpm.
Noisier exhausts were then introduced for round five at Hockenheim in late July.
For the 1980 Procar Championship, FOCA took control of the series as BMW began to look towards an F1 engine supply deal having essentially given up any hope of running works Group 5 M1s.
That season, the ‘works’ cars were prepared by BS Fabrications in Luton and now came equipped with air jacks for quicker wheel / tyre changes. Instead of the traditional white, blue and red BMW Motorsport colour scheme, the ‘works’ cars initially appeared in a white and red livery before switching to a white and green combination from round four at the Norisring in June.
COMPETITION HISTORY
The eight-race 1979 Procar series proved an enormous success and, on account of the cars and drivers competing, went down in history as arguably the best one-make championship ever.
Thanks to wins at Monaco, Silverstone and Hockenheim, Brabham F1 driver Niki Lauda was crowned the winner. Second place went to ATS F1 driver Hans-Joachim Stuck who drove a Manfred Cassani-prepared customer car and took a brace of wins (at Zandvoort and Monza, the last two events of the year). Even though he ultimately failed to win a Procar race, Wiliams F1 driver Clay Regazzoni had looked most likely to challenge Lauda for championship honours, but a DNF in the final race at Monza dropped him to third.
Aside from Lauda and Stuck, the other competitors who won Procar events in 1979 were Shadow F1 driver Elio de Angelis (the season-opener at Zolder for Osella), Lauda’s Brabham team-mate Nelson Piquet (at Dijon driving a works car) and Ligier F1 driver Jacques Laffite (at Zeltweg, also in a works car).
Elsewhere in 1979, after BMW had run Marc Surer in a works Procar at the DRM Nurburgring for its debut race during late April, the factory supplied a single car for a Herve Poulain entry at the Le Mans 24 Hours. This particular example, the fourth in BMW’s Art Car series, was painted by Andy Warhol and came home sixth overall and second in the over 2.5-litre IMSA class.
In addition to various rounds of the Deutsche Rennsport Meisterschaft (DRM), several customer teams ran their M1 Procars in the season-ending Kyalami 1000km non-championship race where the Eggenberger example of Eddie Keizan and Helmut Kelleners emerged victorious.
The nine-race 1980 Procar Championship was won by Nelson Piquet (still driving for Brabham in F1). Piquet’s run to the title followed a late surge that culminated in a hat-trick of consecutive victories in the last three races of the year (Zeltweg, Zandvoort and Imola). Williams F1 driver Alan Jones finished second despite no wins while 1979 runner up, Hans-Joachim Stuck, dropped to third in the standings driving initially for Project Four and later GS Tuning. Stuck took a brace of wins (at Monaco and the Norisring).
The only other participants to win a Procar race in 1980 were ATS and Ensign F1 driver Jan Lammers in a BMW Netherlands customer car (Donington), Williams F1 driver Carlos Reutemann (in a works car at Brands Hatch) and Manfred Schurti (at Avus in a Manfred Cassani customer car).
In 1980 and beyond (the M1 was finally homologated in December 1980), the M1 became an ever present in the DRM, World Sportscar Championship and IMSA where it ultimately proved as effective as BMW had originally hoped.
Text copyright: Supercar Nostalgia
Photo copyright: BMW - https://www.bmw.com & Bonhams - https://www.bonhams.com/department/CAT-MOT/motoring/
