Jaguar’s XJ: Skinning the Cat
Jaguar gets underneath the skin of its new range-topper — and shows the first U.S.-trimmed XJs to boot.
by Ian Norris/ TCC 12/9/2002
When Jaguar unveiled its new XJ sedan at the Paris Auto Show it whetted the appetites of automobile engineers across the globe. Although it’s difficult to tell the new car from the current model at a cursory glance, under the skin this is one of the most important new Jaguars ever.
The reason is its body construction, which is almost completely in aluminum. There is already one major luxury car that features the lightweight metal in its body, the Audi A8, but it utilizes a frame made of aluminum that forms the skeleton of the car and supports aluminum body panels. The Jaguar uses aluminum in a conventional unitary monocoque, and is the first volume production car in the world to feature this type of construction.
The engineers were interested to know how the company had tackled a construction process that has put so many others off aluminum; Jaguar has now revealed some of its secrets by inviting journalists into its body plant at Castle Bromwich at Birmingham in the English Midlands. The plant is still in the preparatory stages of production, as the XJ program moves toward a planned roll-out of production cars next spring. The production rate is low, and the program is running late (the original aim was to start selling cars late this year) but that’s not surprising. Jaguar has taken on a mammoth task and seems to be making good progress.
The problem with aluminum
The problem with aluminum – which is an excellent material for cars because it is light, strong if properly utilized, resistant to corrosion and almost 100 percent recyclable – is that it cannot be welded in production quantities. Welding is the accepted form of constructing conventional steel bodies, and to turn over to aluminum, which has to be riveted and bonded with adhesives, is a major change for any manufacturer.
Jaguar took the giant step because it had decided that the replacement for its current large sedan range had to be lighter. Within Jaguar, the project was called the ‘Light Weight Vehicle’ and its leaders stress that the adoption of aluminum for the body was only one aspect of the weight-reduction program. It was the most important, however, and it has paid off. The overall weight of the new XJ is some 440 pounds below that of the current car, in spite of the fact that the new model carries all the bells and whistles now expected of a top-line luxury sedan. The bodyshell itself makes a major contribution to that slimming process – the new version weighs in at just 485 lb compared with the 793 lb of its predecessor.
Because of the new techniques involved, Jaguar has had to install a completely new press shop and body assembly line at Castle Bromwich, the largest of its three plants and the production center for all its bodies except that of the compact X-Type sedan. The pressshop contains 13 new Schuler presses that will produce 125 of the 235 pressings for the new body; the rest are supplied by outside contractors. In all, there are 339 components in the body, the majority of them in aluminum. In addition to the pressings, there are 15 castings, 28 extruded components, 1 hydroformed unit and 60 steel items.
The bodies are assembled using a combination of rivets and adhesives, with 3180 rivets and 394 feet of adhesive going into each body. Much of the riveting and application of adhesive is carried out by robots, supplied by Kawasaki. Because of the amount of new technology involved in the new body, Jaguar has drawn extensively on outside know-how. Alcan has been closely involved in the project since its inception, a British firm, Henrob, is the sole provider of the riveting technology, and Polynorm of Holland staffs and operates the new press shop on Jaguar’s behalf.
The heat involved in the paint process not only cures the adhesives used to bond the bodies but also bake hardens the exterior body panels, improving their resistance to dents and dings. Nevertheless, the bodies go through the same paint ovens as the XK and S-Type bodies that are also built at the plant.
With air suspension all round, the more powerful engines introduced this year on the existing XJ range and a lighter body, the new car is expected to offer much improved performance and handling over the current car. Jaguar executives are upbeat about its performance, promising 0-60 mph acceleration in 5.0 seconds and a limited top speed of 155 mph for the top-of-the-range XJR, powered by a 4.2-liter supercharged engine. The lightness of the body aids performance and handling, but it also brings advantages in fuel economy and exhaust emissions, both of which are promised to be excellent for a large luxury car.
Jaguar took the opportunity of the press visit to issue the first pictures of the new XJ in U.S. specification, but gave no hints as to what prices are likely to be when the car goes on sale in the first half of next year.
My first car was a 67 Mustang Coupe, 2nd one was a 67 Cougar XR-7, 3rd one was a 66 Mustang Coupe. Why did I get rid of these cars for ? I know why, because I'm stupid, stupid, stupid.
My next Ford.....