Tony Southgate and the XJR-6
It was around this time that Jaguar called upon another major player in the development of their prototype sports car program, one who would see the manufacturer rise to the very top of the sport with a car based on the XJR-5 framework, and subsequent iterations. Jaguars presence had been strongly established in IMSA with the XJR-5, after following entry in the 1984 24 Hours of Le Mans, they looked to develop a car to compete in the World Sportscar Championship and challenge the Porsche 962. They turned to Tom Walkinshaw Racing to develop the XJR-6. TWR was a race team founded in Oxford in 1976. Initially involved in privateer efforts with Mazda and Rover, Tom Walkinshaw built a reputation for winning through successes in the European Touring Car series, securing a championship for Jaguar, a feat which eluded all other British makes that year. Ironically, the title was sealed on the same weekend Group 44 took the XJR-5 to Le Mans. It was a significant accomplishment, proving to Jaguar that it wasn’t only the American team who was capable of coaxing victory from the cars. Through all its racing efforts, TWR was trying to align itself to become the Group C representative for Jaguar. When TWR got its hands on an XJR-5 to begin development of the 6, Walkinshaw simply went through the motions because in reality, he was already preparing a new car in partnership with designer Tony Southgate.
Southgate was brought on by TWR as a consultant, bringing with him an established career which spanned CanAm to Formula One. He had recently finished designed the Ford C100 Group C prototype racer, and using the design as inspiration, he went straight to work on the new XJR-6. The benefit of moving from one finished project to a new one was it gave you the opportunity to keep the good bits, and discard the bad ones. If there were inherent problems with the previous design, you could engineer the problems out. Much like the XJR-5, Southgate designed the chassis as an all carbon fiber tub and bodywork. The aerodynamic properties of the body were developed at the Imperial College wind tunnel in London, where the car diverged from the classic ‘Porsche’ school of thought regarding aerodynamic design. Southgate analyzed the airflow entering the underbody area of the car from both the front and sides. He recognized that better management of side air in-flow was key in unlocking additional potential aerodynamic performance.
To condense the idea Southgate was after into an easier to digest concept, allow me to add to my original topic on ground effect that was brought up during Porsches 962 development. As a car passes through air at speed, the majority travels over the car, and some goes underneath. Like an aerofoil, the air on top must travel faster than the air below the car to cover the same straight-line horizontal distance. Faster air creates higher air pressure, and conversely slow air creates low pressure. Low pressure under the car, as we should know by now, creates suction, pulling the car into the ground and improving traction. If the underside air pressure is very low, it tends to act like a vacuum and pull undisturbed air at higher pressure into the void. This usually occurs at the side of the car. If you could create skirts that run between the front and rear wheels to separate the underside of the car from the ambient air, you create a tighter vacuum, and lower pressure. Class dismissed.
In the same effort, the rear wheel well was sealed off with sheet metal bodywork to encapsulate more air underneath the car’s body. This change alone improved downforce by a staggering 10%.
The XJR-6 first appeared in competition at Mosport in Bowmanville, Ontario in August of 1985. It weighed 920kg in race trim, a certifiable pig compared to the majority of its contemporaries, but despite the baby fat, Martin Brundle was able to hold a lead during the opening laps of the 1000km race. The team of Brundle, Schlesser and Thackwell brought the car home in third spot, another debut from a Jaguar chassis showing immense promise for the future seasons. Later that season, the same car and team scored fifth overall finish at the fateful 1985 1000km of Spa, the same event of Stefan Bellofs death. The race was elected to be cut short by race directors which left the Jaguar where it had been currently running. Finally, an impressive 2nd place finish was achieved at Shah Alam in Malaysia. These being the notable finishes for the XJR-6 during the 1985 season, TWR had an opportunity to use the offseason to their advantage, and extract the winning potential out of the chassis.