Guide: Jaguar XJR-15 - a Historical & Technical Appraisal

Dec 24

Dec 24 Guide: Jaguar XJR-15 - a Historical & Technical Appraisal

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BACKGROUND

Having successfully managed Jaguar’s European Touring Car Championship effort with the XJS between 1982 and ‘84 (a programme that yielded 16 wins and the 1984 Driver’s title), Tom Walkinshaw Racing (TWR) was commissioned to take the British manufacturer into the World Sportscar Championship for 1986.

Ultimately, TWR’s sports car collaboration with Jaguar proved even more successful than their touring car partnership.

In 1988 and 1990, the TWR Jaguar squad secured outright wins at the Le Mans 24 Hours while back-to-back World Sportscar Championship titles were achieved in 1987 and 1988.

During this period, TWR boss Tom Walkinshaw began to formulate plans for a Group C-inspired Jaguar road car, something in a similar mould to the Le Mans-winning C and D-types that were sometimes used as the fastest road cars of their day back in the 1950s.

The machine that followed was dubbed XJR-15.

Announced in November 1990, the XJR-15 was based on the 1988 Le Mans-winning XJR-9, a mule of which (chassis XJR-9R) had been used to test composite materials over thousands of miles and which became the basis for the new model.

However, at the Birmingham Motor Show back in October 1988, Jaguar had displayed their own supercar which was itself given the green light for production. The XJ220 was scheduled to arrive in 1992 and, having been unveiled in the midst of a red hot speculator-driven collector car boom, orders flooded in with Jaguar reputedly taking 1400 deposits for the new machine at £50,000 apiece.

Despite the XJ220's impending arrival, Walkinshaw convinced Jaguar to give their blessing to the XJR-15 and a new jointly owned company called JaguarSport was established to manufacture a batch of 50 examples.

The XJR-15 was given a press launch at Silverstone in early January of 1991 and then a public debut at the Autosport Racing Car Show a week later. Production was expected to have ended prior to the XJ220’s arrival.

Although it was designed with road use in mind, the XJR-15 was also marketed as a one-make racing car to avoid creaming off prospective XJ220 customers.

At $960,000 (£550,000), the XJR-15 was even more expensive than the XJ220 which ultimately retailed at $820,000 (£470,000).

XJR-15 buyers were able to order their car in road or racing trim with the latter eligible for a one-make series called the 1991 JaguarSport Intercontinental Challenge.

The three-race Intercontinental Challenge supported the Formula 1 events at Monaco, Silverstone and Spa. The not inconsiderable purchase price for an XJR-15 included race preparation and maintenance for the series, but any damage had to be paid for separately.

Grid slots were limited to 16 cars. The winners at Monaco and Silverstone each received a Jaguar XJR-S. At Spa there was a $1m cheque for the victor which guaranteed enormous exposure.

CHASSIS

At the core of the XJR-15 was a carbon Kevlar monocoque based on that of the XJR-9.

The existing tub was modified to provide more cockpit space as the original passenger seat had been little more than a token gesture to satisfy the rule makers. At 2718mm, the XJR-15’s wheelbase was 62mm shorter than the XJR-9.

The engine and transmission acted as a stressed member; the engine was bolted to the rear bulkhead and carried the rear suspension.

Ride height had to be increased (the XJR-15 was ostensibly a road car after all) and as this would have affected ground effect, underbody aero was greatly reduced.

Racing suspension geometry comprised double wishbones with pushrod-activated coil sprung dampers (inboard at the front, outboard at the rear). An adjustable anti-roll bar was installed at the front but not at the back.

Cars for road use were configured with a slightly softer suspension set-up for increased comfort.

330mm diameter ventilated disc brakes were fitted all round along with AP Racing four-piston calipers. Brake balance was adjustable from within the cockpit.

The handsome 17-inch forged alloy centre-lock wheels were supplied by OZ Racing. They measured 9.5-inches wide at the front, 13-inches wide at the rear and were originally intended to be shod with Goodyear tyres before Tom Walkinshaw signed a late supply deal with Bridgestone.

ENGINE / GEARBOX

As per the XJR-9, the XJR-15’s engine was a naturally aspirated dual overhead camshaft 60° V12.

This all-alloy power unit was a combination of two earlier race motors: the bottom end came from Group C while the 24 valve head and intake system were derived from the Group A XJS.

Displacement was 5993cc thanks to a bore and stroke of 90mm and 78.5mm respectively.

The engine featured Cosworth forged alloy pistons, dry-sump lubrication, Zytek sequential electronic management, Lucas electronic ignition, a forged EN40B steel crankshaft with Holset harmonic damper and a fly-by-wire throttle.

Compression was set at 11.0:1.

Peak output was 450bhp at 6250rpm and 420lb-ft at 4500rpm.

For comparison, the seven-litre XJR-9 developed 750bhp at 7200 rpm and 611lb-ft at 5500rpm.

The reduced torque from the XJR-15's engine required the use of a six rather than five-speed gearbox for competition use. Built by Hewland, it employed straight-cut gears while cars built to road trim used a five-speed ‘box with full synchromesh for greater practicality.

Transmission was through a triple-plate carbonfibre AP Racing clutch and limited-slip differential.

BODYWORK

Bodywork was designed by Peter Stevens who went on to style the McLaren F1 shortly afterwards. It was manufactured entirely from carbonfibre and frankly made the XJ220 look like a barge.

Simple, elegant and beautiful, the XJR-15 was a match for anything Ferrari or Lamborghini had to offer.

Curvaceous cooling ducts were carved out from the nose and flanks. Covered supplementary lights were housed below retractable main units.

The domed cockpit was inevitably a little wider than the XJR-9 and access was via conventionally hinged doors.

A fixed body-coloured spoiler was mounted at the rear.

The tail fascia was home to a wide cooling grille housed between custom tail lights.

All 50 production cars were originally painted XJR Blue.

INTERIOR

Once inside, occupants were greeted by acres of exposed carbonfibre.

No carpet was installed, nor were upholstered door trim panels or headlining and there was little in the way of sound insulation. The Plexiglas side windows were fixed in position; for additional cockpit ventilation a triangular cutaway flap hinged at the base could be folded down.

The dash was home to a 220mph speedo, 7000rpm rev counter and smaller read outs for oil pressure, oil temperature, water temperature and fuel. Off to the right were a series of flick and push-button switches along with a battery cut-out switch.

Grey leather was used to cover the instrument binnacle and leading edge of the dash top.

Every XJR-15 was right-hand drive with a right-hand gear lever.

Cars built to racing specification came with un-trimmed carbonfibre bucket seats, blue four-point Sabelt harnesses and a three-spoke Personal steering wheel upholstered in black leather.

Those configured for road use had more substantial seats complete with a padded head rest panel. They were trimmed in two-tone grey leather with purple highlights. Road versions came with black four-point harnesses, a grey-trimmed Nardi three-spoke steering wheel and were also supplied with a pair of JaguarSport-branded headphones with intercom.

WEIGHT / PERFORMANCE

The XJR-15 weighed 1050kg in race trim and 1062kg in road trim.

JaguarSport quoted a 0-62mph time of 3.1 seconds and top speed of 185mph.

With longer ratios, in excess of 210mph would reputedly have been possible.

END OF PRODUCTION

XJR-15 production continued until 1992.

Although a production run of 50 units had been planned, 53 cars were ultimately completed of which 18 were to race specification and 35 to road specification.

1991 JAGUARSPORT INTERCONTINENTAL CHALLENGE

The three-race 1991 JaguarSport Intercontinental Challenge was arguably the most spectacular one-make series ever organised. Each contest comprised a grid of 16 cars, most of which were piloted by highly rated professional drivers.

The Monaco event was won by pole-starter Derek Warwick who, having briefly been passed by Armin Hahne into Ste Devote on the opening lap, regained his advantage and led the chasing pack home to win by just over half a second from David Brabham.

After a more-or-less trouble-free event around the streets of Monte Carlo, round two at Silverstone was carnage.

Eleven of the 16 cars incurred some kind of damage in what proved to be a frantic race from start to finish. Derek Warwick was on pole for the second race in a row, but it was Juan Manuel Fangio II that took the chequered flag by just over four seconds from Bob Wollek as most of the more fancied runners picked up damage and were delayed or retired.

The finale at Spa was to be decided over an undisclosed number of laps to avoid any opportunity for race fixing. All the drivers knew was that the event would run for at least six laps.

Cor Euser started from pole, but having nearly gone off at Eau Rouge, he was passed by Armin Hahne on lap eight. Derek Warwick also tried to go through and battled with Euser for the rest of lap until the Englishman lost it in the sequence of fast corners before the Bus Stop. Warwick’s car pin-balled off the barriers in what was the biggest crash of the series.

Hahne went on to finish a little over four seconds clear of Euser to claim the $1m prize.

Text copyright: Supercar Nostalgia
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