Model history: Despite dominating the 1988 World Championship and winning the 24 Hours of Le Mans, Tom Walkinshaw realised that 'his' V12-engined Jaguars were gradually losing competitiveness, especially in the shorter sprint events. The new generation turbocharged engines were both lighter and more compact than the big production-based V12 that had served JaguarSport (a collaboration of Walkinshaw's TWR and Jaguar) so well for the better part of three seasons.
In response JaguarSport started the development of a purpose-built six cylinder engine for the 1989 season. The design permitted for two variants; a 3-litre for the American IMSA series and a 3.5 litre Group C specification for the World Championship, which included the 24 Hours of Le Mans. Taking advantage of the much more compact dimensions of the bespoke V6, JaguarSport's Tony Southgate also designed an all-new chassis. In IMSA form the new car was known as the XJR-10 and the Group C variant was dubbed the XJR-11.
The all-aluminium V6 was loosely based on the engine used in the MG Rover 6R4 Group B racing car. Tipping the scales at just 143 kg, this was a thoroughly modern V6 with twin overhead camshafts and four valves per cylinder. Added to the lightweight unit were two Garrett turbochargers, which boosted the power to around 650 bhp in 3-litre form. The larger Group C engine produced around 750 bhp depending on the level of boost. In both forms, the 'JRV-6' was mated to a five-speed gearbox, which served as a fully stressed member.
With the help of Ross Brawn, Southgate laid down a chassis, which in most respects was a compacter evolution of the successful XJR-6/8/9 carbon fibre monocoque. Suspension was by double wishbones with the front springs and dampers actuated by pushrods and the rears mounted outboard. This unconventional setup freed up more space for the ground-effect tunnels. Both machines received subtly different bodies to suit their specific purpose; the XJR-10 generated more downforce to cope with the tighter American tracks.
The XJR-10 was ready first and it debuted during the May 29 Lime Rock IMSA round. Jan Lammers placed a promising second behind Geoff Brabham's Nissan. In July the XJR-10 finally broke the Nissan stronghold when Lammers and Price Cobb won at Portland beating the two Nissans. Used well into 1991, the V6-engined machine would eventually rack up 6 victories out of 26 entries in the hugely competitive championship, which also saw the Eagle-Toyotas emerge as top contenders in this period. For the long-distance events JaguarSport continued to use the tried and trusted V12-powered XJR-12s.
By July of 1989, the Group C specification XJR-11 was also ready. Like its IMSA counterpart, it faced very strong competition, this time from the Sauber-Mercedes team with their hugely powerful V8-engined 'Silver Arrows'. Lammers and Patrick Tambay did qualify on pole at the Brands Hatch debut but in the race could do no better than sixth. Reliability issues dogged the car for most of the year and only in May of 1990 did the XJR-11 score its one and only victory. As with the IMSA car, the XJR-11 was not used at Le Mans where the XJR-12 was used and driven to victory in 1990.
Rule changes rendered the XJR-11 all but obsolete for the 1991 season. It was replaced by the F1-inspired, V8-engined XJR-14, which was driven to another World Championship for JaguarSport. For IMSA, the all-new XJR-16 was developed, which was driven to 4 wins in the second half of the 1991 championship. In 1992 its place was taken by a mildly modified XJR-14.
With seven victories, the XJR-10 and XJR-11 do not rank as the most successful sports racers produced by TWR and Jaguar. They nevertheless served JaguarSport well for the better part of two seasons. The JRV-6 was later also used in the XJ220 super car. Today the surviving examples are still frequently raced in historic events and are often found at the sharp end of the field.
The first of three XJR-10s constructed in 1989, chassis 389 was campaigned in the IMSA GTP series for the better part of three seasons by the TWR Jaguar Team. Jan Lammers, sharing with Price Cobb on one occasion, won two races with this car in 1989. During the next season, it was raced by Cobb and John Nielsen, who took one victory. In 1991 Raul Boesel gave the car a glorious farewell by scoring one more win at its final outing. Today, the Castrol liveried machine is regularly raced in historic events.