The 1982 World Sportscar Championship saw the beginning of a brand new era in sportscar racing: Group C had been introduced. The new regulations left plenty of room for engineers to go crazy with exotic engine types of various configurations, and gave them access to the odd technologies already banned from Formula 1. Ground effect chassis allowed sleek low drag bodies to be used, which in conjunction with 1000+ horsepower turbocharged engines saw the top speeds soar into figures never seen before or since.
During the 1980’s the category drew massive manufacturer interest, with Porsche, Nissan, Jaguar, Lancia, Aston Martin, Toyota, Mercedes and Mazda all entering the fray. As a result the stakes were higher than ever, and the series’ popularity grew to the point where it was severely threatening Formula 1’s comfy position as the pinnacle of motorsport.
This development had not gone unnoticed by the top brass of Formula 1. Under the direction of one B.Ecclestone and his band of merry FIA men, a plan was drawn up to softly kill Group C and secure the position of F1 as unassailable top dog for good. The attack entailed a drastic overhaul of Group C’s class system, which saw the lower tier C2 class eliminated completely. C2 had been conceived to allow strapped for cash privateers to run relatively cheap naturally aspirated prototypes, as opposed to the multi million dollar C1 category dominated by major manufacturers. With C2 now dead, these teams effectively had nowhere to go but out. The problem was worsened by introduction of mandatory 3.5L naturally aspirated piston engines, with a specification identical to the one introduced in F1 just a year earlier. This meant affordable engines like the Cosworth DFL and BMW M88 had to be replaced by ludicrously expensive F1 designs meant for major manufacturers. For most former C2 teams, this sudden violent switch was just too much to handle.
Many independent outfits left the series completely, which thinned out the grids in a dramatic fashion. Despite this, stubborn Swiss owner/driver Walter Brun decided to stay put. His Brun Motorsport organization had been loyally campaigning customer Porsche’s 962C, arguably the most capable car of the C1 era. The car had suffered weight penalties to bring its speed down to the 3.5L level, but was still eligible for competition during 1991. For 1992 however, the special dispensation would be null and void, so Brun was forced to come up with something else fast.
As Porsche was too busy with its own F1 engine project and had no interest in developing a 3.5L car, Brun Motorsport had to become a constructor out of bare necessity. Luckily the new F1 engine regulations did little to bother Walter Brun, as it had just ended an unsuccessful three season stint in that category at the end of 1990. With his ambitious self-built Neotech V12 project falling through, he turned to one of his old connections within the shady world of Formula 1.
Eventually he was able to secure the latest narrow angle Judd EV 3.5L V8 from former partner Engine Developments. In all out sprint race form, this engine was good for around 620 horsepower, a fraction of what the old turbocharged 962C produced. To make the unit last a full race distance, the already modest power figure had to be lowered even further. A Hewland six speed manual transmission ensured the remaining power would hit the road efficiently. With the crucial engine plans now in order, Brun’s engineers turned their attention to finishing the new car. The Judd V8 nestled in the middle of a tried and true carbon fiber chassis clad in a new style of bodywork.
With the massive loss of engine power compared to the large displacement C1 cars, the strong emphasis on a smooth streamlined body became irrelevant. To maintain some speed, the focus shifted towards attaining higher levels of downforce. As as result the wings on the new C91 were much bigger, and it included a new carefully shaped aerofoil in the nose. Another prominent change was the large airbox on top of the car, necessary to keep the hungry F1 engine satisfied. All in all the package weighed just 750 kg (1653 lbs).
While the C91 was being completed, Brun made do with the 962C. After four WSC rounds the new machine was finally ready for the 430 KM of the Nürburgring GP-Strecke. By this time three major manufacturers had already taken up the new 3.5L challenge.
Competing with the big budget Mercedes, Jaguar, and Peugeot entries was of course completely out of the question for Brun Motorsport. Instead they directed their attention to an old foe coming from a very similar position: former Porsche clients turned constructors Konrad Motorsport and their KM-011 Lamborghini, which was also making its debut.
Because of the recent changes, the WSC was still in a peculiar transitional state. Both the older C1 and the new 3.5L cars were now competing in the same series. To promote its agenda the FIA demoted the soon to be banned C1 machines to “Category 2”, while reserving the front half of the grid for the 3.5L “Category 1”, regardless of qualifying times. Tasked with trying to get the C91 in a good position were former EuroBrun F1 drivers Oscar Larrauri (ARG) and Gregor Foitek (CH).
At the end of the session they had only managed a dismal 1:29.872, only good for 16th on the 21 car grid. The time was four seconds slower than the nearest Category 1 competitor (Spice SE90C), and a whopping 10 seconds slower than the pole-sitting Jaguar XJR-14. Adding further insult to injury, the Porsche 962C Brun had brought as a T-car was 1.6 seconds faster, along with six other Category 2 machines. The disappointing performance was cut short by technical difficulties before the race. As a result the car never made it to the starting grid. Brun Motorsport’s 962C driven by Jésus Pareja (ESP) and Walter Brun himself finished 7th.
At Magny Cours Gregor Foitek was replaced by the more experienced Pareja. This time the C91 started 7th on the grid behind all the factory machinery and in front of the Spice. Sadly the success was blown to pieces along with the engine after a mere 5 laps.
Still filled with ambition, Brun flew the car to Mexico’s Autódromo Hermanos Rodriguez for Round 7 of the 1991 WSC. At the high altitude circuit the Judd engine suffered a substantial loss in power, which saw the car slip down with a 13th overall time. The new class split was in the C91’s favor however, which saw it start 8th on the grid anyway. Larrauri and Foitek were paired up once more, and again only the Argentinian managed to get a race drive. After 31 laps he came in for a pitstop, but had to retire as the starter motor failed when he tried to get back out again.
Another expensive flight took the car halfway across the world to Autopolis, Japan for the 8th and final round of the 1991 WSC. Oscar Larrauri started from 8th position on the grid, hoping to at least finish on this occasion. Unfortunately he was met with disaster for the fourth time. With just 20 laps completed, the gearbox threw in the towel, forcing Larrauri to retire in frustration.
With the season over and not a single race finish achieved, Brun Motorsport turned its attention to 1992. Their reliable Porsche had been scoring points consistently while the C91 failed, but for 1992 it would be rendered obsolete. The string of misfortune put a hefty dent in their budget, and major sponsor Repsol lost interest in the project. Without adequate funding, Brun withdrew its entry into the 1992 WSC season.
The Brun C91 was an ambitious move by a cornered privateer outfit. The Machiavellian machinations of B. Ecclestone and his cronies forced Brun Motorsport to adapt or die. Inexperienced in the world of race car manufacture, Brun did its best to run with the big boys.
Unfortunately persistent technical issues and teething problems squashed any hopes of the C91 being successful. After struggling for half a season, Brun had to leave the WSC in its entirety, just as B. Ecclestone had intended all along.