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  Article Image gallery (22) XJR-7/001 Specifications  
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Country of origin:Great Britain
Produced from:1985 - 1987
Numbers built:5
Designed by:Lee Dykstra for Group 44
Author:Wouter Melissen
Last updated:August 17, 2011
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Click here to download printer friendly versionWith five victories in seven years Jaguar's dominance in the 24 Hours of Le Mans race was total. After the last victory, in 1957, the rules were changed, leaving Jaguar's D-Type obsolete. This effectively ended Jaguar's interest in sportscar racing. Halfway through the 1960s work was started on a completely new V12 engined sportscar, to challenge Ferrari and Ford at Le Mans. One XJ 13, as it was called, was completed and tested, but the project was dropped for unclear reasons.

After Jaguar's withdrawal, it was up to privateers to defend the honours of the leaping cat. One of the premier Jaguar privateers was Bob Tullius, whose Group 44 racing first campaigned a Jaguar in 1974. He won the Sports Car Club of America (SCCA) B production category with a mildly modified V12 engined E-Type. Over the years he kept on competing V12 Jaguars in the SCCA championships and in TransAm. When the new IMSA GTP class was formed, Tullius decided to construct a prototype racer around the V12 he knew so well.

At Le Mans there was a class for IMSA GTP cars, so this could end up as Jaguar's return to the French track. That foresight sparked interested in Coventry and with factory backing work was started in the Winchester, Virginia headquarters of Group 44 racing, early in 1981. The prototype would be aptly dubbed XJR-5; Group 44's previous four cars were XJR 1 - 4.

Hired as designer was Lee Dykstra, whose Special Chassis Inc. had designed a successful ground effects racer in 1980. Dykstra decided to use the long and relatively heavy V12 engine as stressed chassis member. The engine was bolted directly on the aluminium monocoque, supported by four stiffening struts bolted on the firewall. The slim design was completed by attaching the rear suspension on the transaxle, leaving plenty of space for underbody aerodynamics.

Pioneered by Lotus in the late 1970s, ground effects aimed at reducing the air pressure under the car. Grip was created by the low air-pressure 'sucking' the car to the ground. To create ground effects, the underbody of the car was shaped like the top half of an airplane wing. The XJR-5's slim monocoque chassis allowed for large, clean 'wing' surfaces on each side of the engine. After many wind-tunnel tests of quarter scale models in the Williams rolling road wind-tunnel, two underbodies were constructed. A low drag, low downforce version for high speed tracks like Le Mans and Daytona and a high downforce one for slower tracks.

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  Article Image gallery (22) XJR-7/001 Specifications