J. Fuller, 1996
The modern era of sports prototype racing began in 1953 with the implementation of the World Sports Car Championship. The World Sports Car Championship was an organized racing series and was overlooked by a governing body, the FIA (Federation Internationale de l’Automobile-- International Automobile Federation). The FIA organized the series of world-wide races, established rules that governed the design and construction of the race cars, and awarded points relative to the finishing position of a competitor, thereby establishing a competitive environment that attracted the world's best drivers, sponsors, designers, engine and chassis manufacturers, and tire companies.
Throughout the 1950s, the typical sports prototype racing car was small, light weight, front-engined, and was bodied in a slippery aerodynamic shell. Due to relatively inefficient engines that lacked horsepower, race car designers subscribed to making the car look as aerodynamic as possible by designing the body round and streamlined so that it cheated the wind and made up for any horsepower deficits. What the designers didn't realize was that by designing slippery looking shapes, they were providing for the airflow to pack underneath the car at racing speeds and produce dangerous lifting forces on the front axle. The car bodies were more akin to positive lift producing airplane wings and had a tendency to want to take off at high speeds. This made the cars unpredictable and potentially dangerous at the limit.
But this period of race car development was punctuated by one innovator who realized the potential of designing a device that produced negative lift, thereby canceling the positive lift forces that were common. In 1956, Michael May, an engineer, thought that by constructing an airfoil, flipping it over so that it produced a negative force towards the ground, and mounting it onto his Porsche Type 550, he could utilize this negative force, or downforce, to improve the traction, grip, and handling of his race car . But Michael May's innovation was perhaps too successful. At the first race that he introduced his device, the race organizers, under pressure from the Porsche factory team, refused him the opportunity to race sighting that the wing, “restricted the view of the drivers behind him”. Subsequent attempts to run the wing mounted Porsche were denied as well. With that, wing development and conscious downforce generation fell by the side and for the rest of the 1950s the concentration was still on low drag and slick looking bodies.
1963 saw the first win at the prestigious 24 Hours of Le Mans for a car with a mid-mounted engine. This proved beyond a doubt that the mid-engine layout, where the engine is mounted in front of the rear axle, offered substantial improvements in handling and aerodynamics. The 1960s also saw the resurgence in the development of the wing. In 1966 Jim Hall mounted a wing onto his 2E Can Am Chaparral and proved the value of the concept by running competitively in the Can Am championship that year. The next year Jim Hall brought the winged 2F Chaparral to Le Mans and reintroduced the wing concept to the Europeans. By 1968 wings started to show up on Formula One cars and a new era of conscious aerodynamic development began to emerge.
This turning point is exemplified by the development of the Porsche 917. In 1969 Porsche introduced the 917 to international sports car racing. Porsche management was interested in having a race car capable of vying for overall victories, not just the class victories they had come accustomed to. The success they had achieved in the lower classes came about by coupling Porsche's reliable, small capacity, low horsepower engines with sleek, low drag body work designed to achieve as much straight-line speed as possible. This combination was highly successful, but, as stated, over all victories were elusive. With the 917 Porsche decided to design a new, pure-bread, high horsepower racing engine and clothe the chassis in the low drag body work that Porsche had so much experience with. Porsche hoped the 917 would be the world-beater.
But from the outset the 917 was plagued by an aerodynamic instability problem. This instability was due to the relatively massive horsepower increase (from the production based racing units Porsche was used to, to the 917’s 580 racing horsepower) in combination with Porsche's low drag aerodynamic design philosophy . Porsche set out to cure the 917’s diabolical handling nature (the drivers of the 917 had nicknamed it “The Ulcer”). Through extensive wind tunnel and track testing, Porsche ended up modifying and reprofiling the front and rear body work to improve the cars aerodynamic stability. The results was a race car that dominated the Sports Car World Championship in 1970 and 1971.
Between 1972 and 1979 sports car racing fell into decline because of uncertain world-wide economics and frequent changes in the rules by the FIA. The sports cars of this time were typified by open cockpits and minimal downforce generating bodies and wings. These cars were called Spyders. This time period lacked some of the excitement and innovation of past eras, but, by the late 1970s, revolutionary advancements in engines and aerodynamics were being made in Formula One racing that would eventually find their way into sports car racing.
During the late 1970s the French auto maker Renault introduced the turbocharged engine to Formula One racing. Turbocharging was not a new idea nor was the application of turbocharging new to racing, but Renault showed that turbocharged engines could be fuel efficient, reliable, and produce tremendous amounts of horsepower from very small engine capacities. By the early eighties, all competitors in Formula One racing had switched from conventional engines to turbocharged engines. This influenced the sports prototype designers especially since the F.I.A. had introduced the Group C rules (C for Consumption) for sports prototypes that put a fuel consumption limit of 60 liter's per 100 kilometers of racing. The Group C rules did not set maximum engine capacity, and the majority of engine manufacturers embraced the turbocharger as a way of producing large amounts of reliable horsepower within the fuel limits.
Another innovation that would fundamentally change the way sports prototypes were designed was introduced in 1977 by the Lotus Formula One team. Peter Wright and the Lotus design team introduced for the 1977 season the Lotus 78 “wing car”. The Lotus 78’s sidepods were shaped like upside down wings and made use of the well known aerodynamic effect that the lift of a wing increases with decreasing ground proximity (called the ground effect). This created massive amounts of downforce underneath the car which boosted cornering speeds tremendously. The best thing was that it was with very little drag penalty. A standard wing produces more pounds of drag per pound of downforce (therefore a less efficient lift to drag ratio, L/D) in comparison with a contoured underbody (the underbody/underwing is sometimes also called a ground effect tunnel) run in close proximity to the ground. Not to mention the fact that only a small pressure drop per square inch would yield loads of downforce due to the large area of the underbody that was available. Utilizing the underbody shape of the race car to produce huge amounts of downforce was revolutionary and this idea has been utilized throughout motor sports, especially in the sports prototype racing series.
The 1980s sports prototype racing car utilized all of the innovations race bred in Formula One racing in the late 1970s. High horse power, small capacity, turbocharged engines were status quo. Horse power figures of 750 or more were common, and qualifying boosted horsepower numbers of over 1000 were not unheard of. The use of composite materials, such as carbon fiber and Kevlar, introduced in the early 1980s by Ron Dennis and the McLaren Formula One team, in the construction of the chassis, wings, and body work made the prototype cars lighter and stronger. All these elements, coupled with the continued development of ground effects and aerodynamics increased cornering speeds even further. The typical 1980s sports prototype racing car had a turbocharged, mid-mounted engine, an aluminum honeycomb chassis, carbon fiber and Kevlar body work, and highly developed, high down force aerodynamics.
The end of the 1980s witnessed the banning of the turbocharged racing engine by the F.I.A., replaced instead by small capacity, high revving, highly efficient, normally aspirated Formula One type racing engines. This measure was sighted at reducing costs, reducing power outputs, and increasing safety through reduced speeds. The sports prototypes racing cars of the early 1990s were called “two seat Grand Prix cars” because of their Formula One derived engines and astonishing cornering capabilities. The aerodynamic developments of the past were refined even further, and the 1990s sport prototypes, which had less horsepower than a turbocharged 1980s prototype, were even faster.
In comparison of pole qualifying lap times between 1990 and 1992 at the 24 Hours of Le Mans: In 1990, it took the pole qualifying Nissan R90CK turbo car 3 minutes and 27.00 seconds to travel the 8.45 mile circuit at an average speed of 146 miles per hour. In 1992 the pole sitting Peugeot 905B non-turbo car qualified in 3 minutes and 21.21 seconds at an average speed of 151 mile per hour. The Peugeot 905B was quicker over the lap, but the Nissan R90C had a higher top speed at the fastest point on the track, 236 miles per hour versus 220 miles per hour. In analysis, the Nissan R90CK was supposedly developing more than 1000 horespower in qualifying trim while the Peugeot's engine was good for about 715 . An additional difference was that the Peugeot weighed nearly 300 pounds less (1700 lbs. vs. 2000 lbs. for the Nissan) and therefore its braking distances were shorter. But the essential difference was that of the Peugeot's overall aerodynamic superiority over the Nissan and that allowed the 905 to lap faster than the R90CK. The Peugeot did not go quicker over the lap by driving slowly through the corners.
But, as the saying goes, “All good things must come to an end”, and it was the cost of developing such high performance vehicles coupled with the world-wide recession that saw sports car racing fall into decline again in the early 90s. The World Sports Car Championship was abandoned but sports car racing continued in the United States under the International Motor Sports Association's (IMSA) banner and at stand alone events like the 24 Hours of Le Mans in France and the 1000 Kilometers of Suzuka in Japan. Currently the concentration of IMSA and organizations such as the Automobile Club de L’Ouest (ACO- organizers of the 24 Hours of Le Mans race) is to reduce the costs of racing and increase the competition between the competitors. A lot of the technology introduced in the 70s and 80s has been banned due to the prohibitive costs associated with development and application. Ground effect tunnels and carbon brakes have been disallowed and turbocharged engines have been replaced by production based normally aspirated power plants. The new prototypes are called World Sports Cars (WSC) and are a throw back to the Spyders of the 70s with their open cockpits, flat bottoms, and wings. The hope is that with the reduced costs of racing the privateer teams, who once formed the backbone of sports car racing, will come back to make the sport strong.
So, the future of sports prototype racing is far from bleak. Manufacturers such as Ferrari, Ford, Mazda, and Oldsmobile have taken a great deal of interest in the World Sports Car concept. It is guaranteed that further development in the areas of aerodynamics, engines, and materials will be undertaken in order to find optimal performance on the track.
Copyright, Michael J. Fuller, 1996