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Jaguar XJR-15
In the late 1980s, Tom Walkinshaw had seen the potential demand amongst wealthy customers for exotic and expensive cars. There were already customers wanting to purchase Jaguar Group C cars for themselves, and other cars such as the Ferrari F40 and Porsche 959 had found a ready market.
In order to produce the “ultimate Jaguar”, Tom Walkinshaw used the basis of the Tony Southgate designed XJR-9 Group C racer and commissioned Peter Stevens (who was later to design the McLaren F1 car) to create a softer shape more likely to appeal to the target market. Code-named “R9R”, the prototype was fitted with a modified 6-litre version of the V12 race engine used for the Group C racers and would be eligible for both Group C and GTP racing.
Under R9R’s skin, the general layout was similar to the XJR-9, with the rear uprights, dampers and springs designed to fit inside the wheels allowing more room for the underbody venturi tunnels. The front springs and dampers were were housed horizontally above the driver’s legs, as per the XJR prototypes, and inside the car there were also distinct similarities, including the position of the gear shift to the right of the driver.
At the same time as TWR was developing R9R, Jaguar was also working its own road-going supercar in conjunction with TWR – the Jaguar XJ220 – which posed something of a political problem for Tom Walkinshaw. In order to create some distance between the cars, the XJR-15 became a product of the joint-venture company owned by Jaguar and TWR: JaguarSport. To further distance the cars, where XJ220 was sold as a road car, XJR-15 was sold as a racing machine and owners were required to sign up to participate in a special race series developed specifically for the car: the JaguarSport Million Dollar Intercontinental Challenge.
The asking price for the cars – half a million pounds each – also included full race preparation and backup for the race series, and body preparation from JaguarSport. The XJR-15 race series was to be held over three rounds as support races for the 1991 Formula 1 championship: Monaco, Silverstone, and Spa-Francorchamps. The cars could be owner-driven, however most owners preferred to hire professional drivers including Derek Warwick, David Brabham, John Nielsen and Juan-Manuel Fangio II. Winners of the first two rounds would each win a 6-litre Jaguar XJR-S, whilst the bonus for the final round was a one million dollar prize fund.
Round 1 at Monaco was an eventful affair. 16 cars started but the tight twisty circuit was to take it’s toll on the competitors with many of the cars sustaining damage from the crash barriers lining the circuit. Derek Warwick was to take both pole position and the race victory and the only non-finishers were John Nielsen and record producer Matt Aitken.
Round 2 at Silverstone again saw 16 cars enter, with Fangio taking victory (plus an additional two laps having failed to see the chequered flag at the end).
The final round at Spa was won by Armin Hahne who took a half share in the million-dollar prize money awarded to the car’s owner. Cor Euser finished in second place.
Engine:
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· Type: 60º V12 overhead cam, naturally aspirated
· Construction: aluminium-alloy block and heads, forged-alloy pistons, nitrided forged EN40B steel crankshaft with Holset harmonic damper, seven main bearings, cast-iron ‘wet’ cylinder liners, Cosworth pistons
· Bore x Stroke: 87mm x 84mm
· Displacement: 5993cc
· Compression Ratio: 11.0:1
· Valve Gear: two valves per cylinder operated by single chain-driven overhead camshaft per bank of cylinders
· Fuel System: Zytec electronic engine management
· Ignition: Lucas electronic
· Max Power: 450bhp (335 KW) @ 6250rpm
· Max Torque: 420 lb ft (569 Nm) @ 4500rpm
· BHP/Litre: 75 bhp / litre
· Weight: 299kg including clutch and accessories
Transmission:
· TWR 6 speed manual non synchromesh
Body/Chassis:
· Carbonfibre and Kevlar composite construction monocoque chassis with engine used as rear suspension load bearer; lightweight composite and carbon fibre reinforced body with undersurface incorporating ground-effect venturi channels to the rear and regulation flat floor
Running Gear:
· Steering: rack and pinion
· Suspension:
o front: independent with aluminium hub-carriers and wide-based pushrods to spring/damper units mounted horizontally in centre of car
o rear: independent with double wishbones actuating spring/damper units mounted outboard to allow maximum width of venturi tunnels;
o aluminium uprights all round
· Brakes: AP four-pot calipers with 13 inch diameter cast-iron ventilated discs
· Wheels: OZ forged alloy, 9.5 x 17.0 in (front), 13.0 x 17.0 in (rear)
· Tyres: Pirelli PZero, 250/30 R17 (front), 320/35 R17 (rear)
Dimensions and weight:
· Length: 188.9 in (4800 mm)
· Width: 74.8 in (1900 mm)
· Height: 43.3 in (1100 mm)
· Wheelbase: 107.0 in (2718mm)
· Track: 60.5 in (1537mm) front / 62.0 in (1575 mm) rear
· Weight: 2,315 lb (1050kg)
Performance:
· Max Speed: 185 mph (297 km/h) – limited by gearing
· 0-60mph: 3.1 seconds
· Power to weight ratio: 0.43 bhp / kg
· Fuel consumption: 12 mpg
Chassis
The XJR-15’s composite chassis is based on that of the Le Mans winning XJR-9 designed by Tony Southgate. However, neither the carbonfibre and Kevlar construction nor the monocoque design is the same. In the XJR-15 the tub has been modified to accommodate two occupants comfortably - the XJR-9, like all Group C cars, is really just a wide-bodied single seater with technically just enough room to fit a passenger. Likewise the underbody ground effect venturi tunnels, although of similar width, are much reduced in depth compared with the race car.
The engine and transmission, like that in the Group C Jaguar, are used as a stressed member bolted to the rear bulkhead of the central tub and upon which is mounted the rear suspension.
Suspension
The suspension remains very similar to the car’s Group C forebear: wide-based fabricated wishbones at the front, actuating pushrods to centre-mounted horizontal spring/damper units mounted above the footwell. At the rear the dampers are mounted within the wheels to maximise the space available for the underbody aerodynamics.
Large 13-in diameter ventilated discs and four-pot calipers take care of the braking.
Transmission
For racing, unlike the XJR-9’s 5-speed transmission, the reduced torque from the XJR-15’s V12 engine necessitated the use of six-speed manual, non synchromesh, transmission. As part of the road-going conversion kit, a five-speed synchromesh was an optional extra at £50,000. Power was delivered via a triple-plate, race-spec carbonfibre clutch to the massive 13-in wide rear wheels.
Engine
The XJR-15’s V12, all alloy 6-litre engine was actually an amalgamation of two different race power plants. The bottom end is straight from the Group C cars, whilst the top end and intake system are taken from the XJS Group A racer of the mid-’80s.
With the aid of a Zytec electronic management system, the single-cam, two-valves per cylinder engine produced 450bhp at a rev-limited 6250rpm and 420 lb ft of torque at 4500 rpm.
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[ 本帖最後由 Raybirg NSX 於 2009-10-4 06:57 PM 編輯 ]
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