The New XJ - The Most Advanced Jaguar Ever
Published: 3rd December 2002
Precise Weight-Saving Construction
With the basic design elements of a considerably larger car in place, the engineering team quickly realised that a breakthrough was needed to solve the weight dilemma. At the same time, the challenge was to enhance the performance capabilities and comprehensive list of luxury features the new XJ would offer its customers.
Compromise was unacceptable – and aluminium was the answer.
Intensive studies led by Jaguar engineers at the Whitley Engineering Centre in Coventry, UK had already exposed the potential value of an aluminium-intensive body structure joined in an innovative fashion using rivets and adhesives. It was soon very apparent that this was the direction to take.
"We chose the lightweight vehicle architecture for the new XJ not because it was something new," says XJ Chief Programme Engineer, David Scholes, "but because it would help us deliver significant benefits for our customers. Ultimately, they may not care whether the body structure is aluminium or steel, but the Jaguar customer does care very much about performance, dynamics, fuel economy, emissions and safety. The choice was clear."
The new XJ’s body structure comprises pressings of sheet aluminium combined with aluminium alloy extrusions and aluminium castings. Jaguar’s engineers adopted the proven construction techniques of the aerospace industry to assemble this structure and in volume production, the new Jaguar XJ represents an industry-first use of rivet-bonding construction for an aluminium-intensive monocoque body.
Rivet-bonding uses self-piercing rivets and epoxy adhesives for strength, robustness and durability when joining aluminium pressings. The adhesives applied robotically during assembly, heat-cure to optimal strength during the vehicle painting process. Approaching 3,200 rivets are used in the construction of the new body.
The body of the new XJ is significantly stiffer – by 60 per cent – and lighter by 40 per cent than its predecessor. The strength of its architecture also represents a groundbreaking advance in crashworthiness.
In addition to the advanced nature of the body construction, the craftsmanship and precision evident in the new XJ are indicative of Jaguar’s determination to ensure customers experience total satisfaction.
Panel gaps are smaller and even more precise than in the previous model. Door shut lines are designed with a uniform gap of 3.8 mm to the bumper, sill and an adjoining door. The doors open wide – front doors to 62 degrees, rear doors to 65 degrees – to assure ease of entry and exit for occupants.
The bonnet and boot lid both use four-bar-link hinges equipped with gas-assisted struts, and gaps on these major closures are also extremely precise at 3.5 mm from bonnet to bumper and bootlid to bumper. Extensive use of lightweight components in key areas of the structure ensured the new XJ met the weight targets set by the engineering team. These areas include:
- Bake-hardened aluminium sheet metal pressings for the new XJ’s exterior panels, offering added resilience against dents and dings
- High-pressure vacuum aluminium die castings for suspension and driveline component mounting points, which are both lightweight and highly resistant to bending and contribute to the precision and comfort of the XJ’s steering, ride and handling
- Aluminium alloy extrusions, utilised in the door structures for high strength against potential aerodynamic wind noise and for enhanced security, are also found in the front and rear bumper beams and used for floor and roof reinforcements
In addition, magnesium – as strong as aluminium but 30 per cent lighter again – is used for the new XJ’s seat frames and the cross-car beam that supports the dashboard, instrument panel and steering column.
