XJR-15 Specifications and Detail

Engine:

  • 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:
    • front: independent with aluminium hub-carriers and wide-based pushrods to spring/damper units mounted horizontally in centre of car
    • rear: independent with double wishbones actuating spring/damper units mounted outboard to allow maximum width of venturi tunnels;
    • 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.