The following information is from a press release dated 10-5-2005:
Lightweight Vehicle Technology
- Chassis consists of riveted and bonded aluminium
- All-aluminium construction gives best-in-class torsional rigidity for Coupe and Convertible
- Lightweight body structure means better performance, handling, safety, and economy
- Volume production of aluminium monocoque body structure unique to Jaguar in the automotive industry
Key to the all-new XK’s character is Jaguar’s industry-leading bonded and riveted aluminium monocoque body structure, introduced with the latest XJ saloons. The aluminium body incorporates the latest thinking in epoxy bonding and riveting techniques to produce a chassis that is very safe and very light. In fact the new XK’s aluminium chassis is significantly lighter and stiffer in both Coupe and Convertible form than the steel model it replaces. The new Coupe chassis is over 30 percent stiffer than the previous XK, while the Convertible is an impressive 50 percent stiffer.
As a consequence the new XK accelerates faster, uses less fuel and produces lower emissions than the model it replaces, while offering high levels of safety, reduced noise and vibration intrusion, and improved ride and handling characteristics thanks to improved suspension dynamics.
Jaguar’s Lightweight Vehicle Technology is unique in the industry as a complete aluminium monocoque body structure as distinct from an aluminium spaceframe with separate aluminium panels. Developed from aircraft industry methods, where strength is critical, Jaguar’s manufacturing process produces a massively strong but very light structure. The new XK takes the concept a step further with extended use of lightweight aluminium castings and extrusions as well as the pressed aluminium panels. Its strength and light weight come from the way the shell is constructed, using new jointing technologies developed by Jaguar and its suppliers.
There is only a single welded joint in the new XK Coupe body, the one ‘cosmetic’ joint on the roof. That also has an environmental benefit in that the body construction needs no high electrical current, produces no welding sparks or fumes, and needs no water for cooling. All the other joints in the new XK shell are formed using Jaguar’s unique combination of riveting and bonding. Most joints are produced using self-piercing rivets applied by hydraulic pressure against a fixed tool. Where access to only one side of the joint is possible, as in some of the new extruded box sections, a new riveting process has been developed; and where particularly high stiffness is required in a joint, a combination of riveting and bonding is used – with the adhesive bond in effect creating a continuous joint which is stronger than a similar, riveted-only joint. All visible exterior panels are bonded to the underlying structure, and a new automated seam-sealing process seals all relevant areas of the shell before painting, to ensure that no gaps are missed.
In the new XK, a secondary front bulkhead of aluminium and composite materials helps reduce noise transmission from the engine compartment and provides a dry area under the bonnet for accommodating electrical components. The new structure also has benefits in refinement; castings used for the mounting points for the engine, transmission and suspension make those points significantly stiffer, further reducing transmitted noise and helping to improve suspension dynamics. In terms of long-term strength, Jaguar’s all-aluminium shell has durability approaching twice that of a traditional spot-welded steel body.
Another major advantage of this Lightweight Vehicle Technology is that all the necessary stiffness is in the structure of the body shell, with very large rectangular-section side sills. So the Convertible, even without a roof, does not need the traditional additional stiffening panels seen on many other convertibles - meaning no added weight and no penalty in stiffness or refinement. The aluminium monocoque construction is the biggest contributor to the low overall vehicle weight of the new XK, and the Coupe shell is over 30 percent stiffer than the previous model, while the Convertible boasts an impressive 50 percent improvement in torsional rigidity.
That lightweight body significantly also offers a 10 percent improvement in power to weight ratio. The all-new XK is up to 90 percent stiffer and 180kg lighter than key rivals, with a kerb weight of just 1595kg. In Convertible form the BIW weight, at just 287kg is 19 percent lighter than the previous XK Convertible.
“The lightweight vehicle architecture really helps the all-new XK to handle, steer and brake better than ever,” says Al Kammerer, Jaguar’s product development director. “Imagine how much easier it is to turn a lightweight object travelling at speed compared to a heavy one. The aluminium chassis makes the XK so much more controllable in corners and a whole lot of fun to drive!”
Safety is another major benefit of this very strong construction method. That is partly inherent in aluminium as a material, which absorbs significantly more energy per kilogramme of material weight than steel when it is deformed. But the strength advantage doesn’t only apply to high-speed impacts, it also means lower-speed accident repair costs are kept to a minimum. The reduction in the number of joints in the all-new XK further increases strength, and the front of the body is protected by easily replaced ‘crush cans’ that absorb the energy in impacts up to 15kph.
The all-new XK’s all-aluminium doors are each over 6kg lighter than an equivalent steel door and their mountings are significantly stiffer, which allows smaller gaps. Mounting the window glass rails directly to the aluminium castings at the front and rear of the door gives better sealing from the frameless layout, and an impressively solid sound and feel when closed.
The all-aluminium Liftback rear door is strong, light and simple to operate. Once it has been lifted manually through the first 20 per cent of its opening arc, gas struts lift it the rest of the way.
With lower weight and higher strength, Lightweight Vehicle Technology is the starting point for improved performance, safety, refinement, economy, emissions performance and driving dynamics in the new XK.
Jaguar AJ-V8
The latest AJ-V8 engine was developed to satisfy Euro 4 emissions requirements. Compared to the Euro 3 requirements, that meant a 50 percent reduction in hydrocarbons (HC) and oxides of nitrogen (NOx) and a 60 percent reduction in carbon monoxide (CO) emissions. The new engine also satisfies more stringent American regulations requiring a 50 percent reduction in HC emissions. It features Exhaust Gas Recirculation and the latest generation of catalyst cores with thinner coatings of higher density catalysing material – which reduces exhaust gas restriction and is more efficient.
The major difference between this engine and the previous generation 4.2 litre XK engine is in the fuel injection technology. This latest V8 now uses multi-hole injectors, which improve the fuel spray pattern in the combustion chambers, improving both power and fuel efficiency.
Optimum throttle response (a crucial ingredient in confirming the new XK’s sports car character) is delivered by full ‘drive-by-wire’ electronic throttle control, with no mechanical connection between the accelerator pedal and the throttle body. The response is based on the torque demand for every instantaneous driving situation. That is calculated by the electronic engine management control, based on parameters including the driver’s accelerator input, and other vehicle factors such as road speed, engine speed and gear selection. The electronic controls then call up the required torque at any instant by adjusting throttle position, variable cam phasing, fuel flow and exhaust gas recirculation settings.
Equally important for its new role in Jaguar’s sportiest cars, the 4.2 litre engine has been engineered to give the sound expected from a real sports car engine – especially under acceleration – but without being undesirably noisy. The new XK’s Semi-Active Exhaust system varies the flow of exhaust gases through the main, large silencer box depending on the pressure in the system, and features acoustically tuned tailpipes that eliminate low speed boom. There is also an underfloor resonator with two chambers (one for each cylinder bank) which balances the sound from the two banks. By tuning the sounds from the air-induction system and the exhaust system, Jaguar concentrated on both the solid, powerful low-frequency sounds and more technically ‘sophisticated’ higher frequency sounds, to give a feeling of power and performance.
More Interior Room
There is 59mm more seat-track travel, 54mm more front leg room, up to 31mm more front head room and 32mm more shoulder room [than the previous XK].
There are more interior stowage spaces, and the combination of more interior space plus longer seat travel effectively increases rear seat space and makes rear seat access through the long doors easier.