Production Jaguar XJ220 In Detail

Suspension

The XJ220 runs on double wishbones all round, machined from solid alloy, with the exception of the lower pair at the rear which are welded fabrications with an airfoil section to minimise the disruption to the airflow through the underbody venturi tunnels. At the rear, the suspension is mounted to the engine subframe rather than the transmission itself.

Rocker-arm operated Bilstein spring/damper units control wheel travel, and anti-roll bars are used front and rear. The stub axles are machined forgings with centre-nut wheel retention. Steering is by rack and pinion without any power-assistance.

Chassis and Body

The XJ220’s structure is based on race car technology. Two-inch thick aluminium honeycomb panels run almost the whole length of the car, joined by both honeycomb and machined bulkheads with more honeycomb for the floor panels and centre tunnel, which houses all the wiring and pipework that run through the length of the car. The bulkhead at the front of the driver’s compartment is machined from solid alloy plate, while more machined alloy beams run behind the cabin and under the engine. The two bulkheads behind the cabin house the 90-litre bag-type fuel tank between them, positioned on the car’s centre of gravity to minimize weight transfer changes as the fuel load decreases.

The engine and transmission are mounted into a machined and bolted together alloy subframe which in turn bolts to the tub behind the cabin, stiffening the total structure. A cross-brace connects this frame to the steel roll cage that runs up unobtrusively inside the roof pillars.

Aerodynamics

The XJ220 was the first production road car to use ground-effects to generate positive downforce at speed. At the front of the car, the low nose and spoiler restrict the amount of air that passes underneath the car, whilst any air that does pass underneath the car flows along the smooth underbody without disruption. At the rear of the car are positioned two large venturi tunnels. Gradually increasing volume inside the tunnels causes a drop in air pressure inside them (the Bernoulli Effect), whilst the higher pressure present on the top surfaces of the car attempts to equalise this difference resulting in a positive downwards force, pushing the car into the road.

The cars high speed stability was further assisted through the use of a large rear wing, and at 200 mph, the XJ220 generates 600 lb of downward force.

Generating positive downforce does compromise the XJ220’s drag coefficient, however the resultant coefficient of 0.36 was seen as a reasonable compromise between outright top speed and stability.

Engine

Originally the XJ220 was to have been powered by a highly developed version of Jaguar’s long-lived V12. Instead, when JaguarSport created a production version of the car, they turned to the racing V6 used in Group C and IMSA. The bore and stroke are identical to that of the Gp C engine, but the alloy block is a new casting to allow the normal road car ancillaries to be fitted. The engine’s four valves per cylinder are driven by double belt-driven overhead camshafts per bank of cylinders and operate in a different combustion chamber shape, compared with the race engine, in order to optimise the fuel injector position for clean emissions. The valves differ to those used in the race engine by being 2 mm smaller in diameter. Other differences include a conventional one-piece gasket for the road version, as opposed to the individual cylinder sealing used for the race engine.

Twin Garrett T3 turbos, water-cooled with integral wastegates run at 1 bar pressure in an engine with an 8.3:1 compression ratio. The turbo setup was chosen to give a good spread of torque along with economy and power.

Cutaway drawing of the production Jaguar XJ220