Seventh Generation Jaguar XJ Saloon – X350
Jaguar’s Lightweight Champion
For many years Jaguar had made limited use of aluminium in car production but for the new millennium a radical method of build was announced.
It was the shortage of steel in the immediate post-war years that dictated the use of aluminium for the Jaguar XK120. This was out of necessity as steel was rationed and only available if the manufacturer could prove the product was for export to earn much-needed revenue. Jaguar Cars, as it had become in 1945, made steel-bodied models such as the Mark V of 1948 which could be exported and earn money for a cash-strapped Britain.
The XK120 had been designed to showcase the six-cylinder XK engine and was only ever intended to be a limited production model; thus it did not qualify for a steel allocation and in the end only the first 240 cars were alloy-bodied. The car was not designed for volume production in aluminium and once export orders poured in for the two-seat XK120, the only course was to build it in steel and Jaguar was able to apply for a steel allocation.
Matters improved during the next decades; steel was the preferred choice for volume production with the use of aluminium, to save weight, and reserved for some panels, such as bonnets, boot-lids and in a few cases the roof. This light and strong alloy was used by Jaguar, and by several other mainstream car makers for this application. Aluminium, though, was used by some of the specialist builders, such as, for example, Healey-Tickford and Aston Martin, whose volume production was smaller than Jaguar and others. Though, of course, an exception to the rule was Land-Rover whose world-famous four-wheel-drive vehicles were fitted with an aluminium body. Jaguar used aluminium for the C- and D-types, which were hand-built in limited numbers.
Working with Alloys
Aluminium alloy is attractive to a motor manufacturer, as it is light and does not rust, it is, however, expensive and notoriously difficult to mould, press and spot-weld. To make more extensive use of it would require major changes in engineering and manufacturing technology, and both the Ford and Jaguar engineering teams were studying available methods of build, together with advances in technology. To gather more information they turned to the aerospace industry which had been using aluminium for decades. They concluded that an all-aluminium body-chassis structure could be made and would weigh some 20 per cent less than an all-steel equivalent. It meant that a chassis could be built that was significantly lighter than a steel counterpart, helping to improve fuel economy and lower emissions; every 100 kg saved with an aluminium chassis helps to reduce the vehicle’s CO2 emissions by 9 g/km.
Ford had worked on a method, which they patented, to develop and adapt aerospace technology for car manufacture. In the US Ford trialled the new build technique on sections of their very successful F150 pick-up. Ford wanted to take the process further and decided to use the low-volume Jaguar as a ‘test-bed’ for the new manufacturing technology. Consequently, further investment and development of the technology was going to be required in building of the next generation Jaguar XJ saloon; given the internal factory code X350. While aluminium was already in limited use by Jaguar in production, the alloy was now going to be used to a greater extent than ever before for the new model.
Having made the decision to use aluminium the work began on designing and having the necessary presses and moulds made. Alongside this work there was the urgent question on what was required as a replacement for the X300 and X308. To get the answers Jaguar turned to its US dealers and carried out a survey to find out what sort of ‘sedan’ would sell to new customers as well as to the existing client base. Their conclusions, and the solutions from the design team, will be dealt with later but it would be pertinent to note that Geoff Lawson, Jaguar’s Design Studio Director, would be influenced by the market research. Work on getting the aluminium-build technology right was paramount and whatever engineering and manufacturing processes were decided on the X350 would become standard for Jaguar models in the future.
Studies led by Jaguar engineers at the Whitley Engineering Centre – working closely with their colleagues in Ford Research Laboratories in Dearborn, USA – had already shown the potential for adapting aerospace-style rivet-bonding to create a body shell from aluminium instead of steel. The technology delivered not only significant weight savings, but also major advances in body stiffness, benefiting vehicle dynamics, safety, refinement and durability. Once in volume production, the X350 would represent an industry-first use of rivet-bonding construction of an aluminium-intensive, conventionally structured monocoque body. Rivet-bonding uses self-piercing rivets and aerospace epoxy adhesives for strength, robustness and durability, when joining aluminium pressings. Though the structure was light it was strong and as Chief Programme Engineer David Scholes said at the time: “The creation of this lightweight vehicle architecture required high levels of precision and engineering craftsmanship and Jaguar is uniquely positioned to deliver.” Arriving at that stage had not been an easy route. Scholes added: “Computers do not engineer cars, people do. Our tools are designed to enable every member of the engineering team to achieve the excellence that is the hallmark of Jaguar. Aluminium manufacturing is also quieter, cleaner and requires less energy than traditional steel chassis construction, while recycling aluminium consumes just five per cent of the energy of creating raw aluminium, without compromising the structural integrity of the material. All of this helps to reduce the environmental footprint of a Jaguar before it even hits the road.”
The X350, as an XJ, was going to be a large saloon and David Scholes and the engineering team quickly realized that a breakthrough was needed to solve the weight dilemma, while simultaneously enhancing the performance capabilities and comprehensive list of luxury features proposed for the X350. The aluminium body of the X350 incorporated the latest thinking in epoxy bonding and riveting techniques. At the time, Jaguar’s Lightweight Vehicle Technology was unique in the motor industry, as they envisaged 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 took the concept a step further with an extended use of lightweight aluminium castings and extrusions as well as the pressed aluminium panels. Its strength and lightweight came from the way the shell was constructed, using new jointing technologies that were developed by Jaguar and its suppliers. As we have noted, Jaguar adopted aerospace methods of building the X350 and specially designed presses and robots had to be ordered and, unlike the robots that were found welding in other factories, the robots for the X350 had to rivet and glue panels. The rivets and adhesives were heat-cured to optimal strength during the vehicle painting process, where the chassis was baked to 170ºC in the paint shop. The adhesive in the airtight aluminium sandwich became concrete-hard, turning the thin aluminium sheet into a phenomenally rigid structure, resulting in a body that was extremely strong but light in weight. The presses from Schuler AG in Germany were installed in two lines at Castle Bromwich:
- Line A of six presses produced the major body pressings, such as exterior panels and floor sections.
- Line B consisted of seven presses and was used to create smaller stampings required for the body architecture; the line could be configured into smaller lines as required.
Genesis of the X350
Under the ownership of Ford the well-known and well-loved XJ model would continue, by now in its XJ40 phase and considerably improved and developed. Lawson used the XJ40 as a starting point and clothed the existing structure with new panels that harked back to the curves of the original XJ6. While the resulting X300 (and later X308) was in production, the next generation XJ was under consideration. This version was one that would compete with the latest designs from Mercedes-Benz, Audi and BMW. These manufacturers had evolved several models during the lifespan of the XJ40-X300-X308 and Jaguar and Ford wanted a model to take and effectively catch-up and if possible overtake the Germans. Ford had the resources and did not stint when it came to financing the new Jaguar saloon.
To arrive at a suitable ‘look’ for the new model various style clinics and seminars were held, mostly in the United States where the main market for Jaguar saloons lay, to canvass the views of dealers and potential customers on what was required. This would be a blend of the old and new, though the clinics and forums identified that the XJ also had to evolve to address the requirements of luxury saloon customers, including the demand for more interior space but without sacrificing performance. Tackling this without losing the distinctive proportions and character of the XJ was undeniably a challenge for Lawson’s team.
Though the design team were maintaining visual links with the Jaguar XJ line, the larger X350 posed an even greater challenge for Jaguar engineers. Equipped with even more features, as well as being bigger, could mean increased weight. Without innovation, the new vehicle would have suffered in terms of performance, fuel economy and range, and emissions. Coupled with the reports from the different clinics that had been held the X350 would emerge, after various interpretations with a face similar to that of the outgoing Jaguar X308.
To reconcile the challenges posed by the significantly greater vehicle feature specifications, greater power, increased luggage space, fuel economy and emission targets, Jaguar decided to embrace ground-breaking technology for the X350. Having decided to build the new car in aluminium the next stage was to install suitable new equipment at Castle Bromwich. This was another example of major investment by Ford and Jaguar for the future. First, all the new assembly processes required to create an aluminium-intensive body structure were designed in virtual-reality and Jaguar invested in the latest Computer-Aided Design, Engineering and Manufacture Programmes (CAD, CAE and CAM), all integrated by a process known as Product Information Management (PIM). The latter is basically method of sharing information quickly and efficiently. This meant that anyone involved with the X350 programme could access the information they needed, no matter where they happened to be located. Importantly, PIM enabled engineers to see how any component changes or modifications would impact on their own and that of their colleagues work.
Fergus Pollock was appointed Overall Project Manager, with exterior styling of the seventh generation XJ entrusted to principal designer Tom Owen along with Sandy Boyes, all under the directorship of Geoff Lawson. There were some nods in the direction of the original XJ6, such as the headlamp arrangement and later in the design of the slatted radiator grille.
Work on the X350 commenced in 1996 and was sometimes hampered by Sales and Marketing who came up with demands on the design; for example on one occasion they insisted that there had to be a specific capacity in the boot, this from one of the questionnaires at a forum. Had the design team followed their directive the boot would have ended up halfway up the rear screen. Lawson was not about to be dictated to by this and had a clay made showing the enlarged boot. When the Sales and Marketing department viewed the result they were, rightly, horrified and said that it would not do. Lawson explained that he could not take up any space forwards in the cabin because of the rear seats and could not go lower as that would interfere with the exhaust and ramp angle. The boot could not be made wider as the track was already determined and they could not extend the boot rearwards because of the overall length. The only way was vertically, as he demonstrated in a very graphic manner. They backed down and allowed the design team to get on with the X350. These demands were understandable as they were from dealers and existing customers to the Sales department, who had to pass on the information. Not always easy for sales or design.
Like the S-Type and more so with the X-Type, digital imaging had been used extensively to model and view on-screen variations of the X350. By 1997 the design was well advanced and several four-tenths scale models were made and photographed; four were chosen to be submitted to further market research clinics in the UK, the USA and Japan. Two of the models had sloping front ends and they were not liked; the other two were deemed ‘more Jaguar’ and scrutinised further. Another scale model was made during May 1997 with half showing the sloping front and the other half the preferred design for further comment.
The ‘more Jaguar’ half was making an impression and another scale model, given the design letter ‘T’, was shown and this was chosen as being the ‘most Jaguar-like’ by those canvassed. A new model incorporating the suggested changes was made and presented to the Jaguar board in February 1998. They were impressed, some alterations were requested and a full-size clay was commissioned. This clay was considered by the board and more alterations were incorporated; though the resulting model did not meet the aerodynamic or boot-space requirements it was accepted as the final design for X350, though subject to further refinement and change as necessary. Now the process of arriving at a suitable Jaguar saloon that would satisfy the customer base and the Jaguar management went ahead. All changes were subject to it being possible to actually manufacture them in aluminium, which behaves quite unlike steel when pressed and moulded into shape. First all the new assembly processes required to create an aluminium-intensive body structure were created in virtual-reality, another first for Jaguar.
As we have noted, Jaguar adopted aerospace methods of building the X350 and specially designed robots had to be ordered and, unlike the robots that were found welding in other factories, the robots for the X350 had to rivet and glue panels. The rivets and adhesives were heat-cured to optimal strength during the vehicle painting process, resulting in a body structure that was extremely strong but light in weight.
Each X350 stressed aluminum monocoque used 15 aluminum castings, 35 extrusions and 284 stampings bonded using some 3,180 self-piercing zinc-coated boron steel rivets and 390 ft (120 m) of heat-cured epoxy resin adhesive. In addition to the rivets, which do not require a predrilled or punched hole – each rivet making its own hole on insertion – the process also uses a small number of nuts, bolts, and spot welds. Castings and extrusions accounted for about 11 per cent of the XJ bodyshell.
The exterior and interior structures of the bonnet and boot were assembled using structural adhesives and a joining method called spot-clinching, in which one metal surface is physically clinched over the other in a series of joins similar in size to spot-welds. The edges of the bonnet and boot were finished with a special ‘anti-flutter’ adhesive to reduce wind-noise potential.
To reduce front-end collision repair cost and ameliorate increased insurance rates associated with aluminum construction, the body was designed to withstand an impact of 10 mph without structural damage and used a bolt-on front-end module (BOFE). A hydroformed aluminum extrusion with an energy absorbing foam cover formed a bumper beam cross-member, to provide strength and ‘crushability’ in the event of a minor collision. Steel was used for front and rear subframes and magnesium (as strong as aluminum while 30 per cent lighter) was used for seat frames and lateral instrument panel beam.
Chief Programme Engineer, David Scholes recalled: “We chose the lightweight vehicle architecture for the new XJ not because it was something new, 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. So the choice was clear. We wanted to produce one of the world’s safest cars, and the body structure is the foundation of its excellent safety performance.” Worth noting is that, despite its light body, the X350 XJ was one of the first cars to pass the stringent new US crash standard regulations. To establish the X350’s safety credentials, Jaguar used its own ‘Real World’ crash-test programmes; the engineers performed more than 500 computer-simulated crash scenarios using crash-modelling software before following this up with physical tests. Once they were satisfied with the computer results, some of the prototype X350s were used in real crash tests, as required for certification.
Progress with X350
At the time, the late 1990s, aluminium technology was not as advanced as it is today, and a great deal of credit has to go to Jaguar for pioneering some of the build techniques. Having chosen aluminium over steel, Jaguar found that they could not mould the alloy to the exact lines of the design and changes had to be made. Some of the well-loved curves for which Jaguar is known had to be modified. These changes gave the X350 a more angular look, for example the C pillar was made more upright, whereas it originally paid tribute to the original XJ6 in shape.
All these changes to the overall profile of the X350 were made as the teams worked on the alloys and the designs. It was very much a learning curve for Jaguar and one that would help in the future.
Compared with the previous generation XJs, the overall body of the X350 was wider, longer and taller, with increased head, leg, shoulder and luggage space. It also carried a 0.32 coefficient of drag. Door shut lines were engineered uniformly to a 3.8 mm gap to adjacent body elements and the bonnet and boot were engineered to 3.5 mm to adjacent body elements.
Testing, of course, was carried out by teams in the Middle East, Alaska, Arizona, Europe and the UK and interestingly, once the prototypes had completed their test cycles they were checked and subjected to another round of the same tests. The engineers were pleased with the results and on the way that the X350 had coped. As Scholes commented: “Even before the XJ was introduced to the public the prototypes had already been driven over two normal lifespans (of the car).”
Giles Taylor was given the task of designing the interior of the X350. He gave it more space in the cabin than that of the outgoing models, more head and legroom and kept the usual Jaguar luxury trim. The interior had been designed with great care and was better appointed than before; wood veneer fascia and door trims were available but modified to give a more modern look. This XJ was also liberally-equipped with labour-saving devices: sixteen-way electrically adjustable seats, two zone climate control was also standard with four zones available on long wheelbase models (optional on SWB). Another option was the touch screen interface that controlled default settings, satellite navigation, an Alpine audio system, and blue tooth telephone. ‘Jaguar Voice’ offered voice control of many functions. Jaguar’s ‘quiet glass’ reduced external noise and gave occupants a sense of serene isolation. Coupled with the exceptional suspension and insulation the car rode all road surfaces effortlessly and noise was minimal. Reviewers commented that while the X308 had been a great improvement on the X300 the latest XJ surpassed those models by a comfortable margin.
Adding to the comfort was the multi-link layout, with four-wheel self-levelling adaptive air suspension instead of the previous generation XJs double wishbone Independent Rear Suspension.
Suspension was controlled electronically, requiring no intervention from the driver, (unlike other manufacturers Jaguar did not provide any driver control of ride height or suspension mode) which was fully computer-controlled to adjust damper settings (in milliseconds) and adjust ride and handling under varying conditions, its electronic control system was marketed as Computer Active Technology Suspension (CATS). The air suspension was designed to activate every 24 hours to level the vehicle when parked and not in use. Air suspension was fitted all round which provided adaptive damping as well as rear self levelling. Dynamic stability control as well as traction control were fitted as standard.
Unfortunately, while the progress of the X350 was well under way Lawson suffered a stroke and died. Ian Callum, who had been with TWR was appointed as Director of Design. There was little he could do to change any details of the design, which was far-advanced and nearly ready for production, but he was able to consolidate the team’s work and also added a few touches of his own. Callum takes no credit for his part in the X350 as he feels it was all down to Lawson, Pollock, Owen and the team. Though he would have liked to see a different XJ, he comments that the X350 “… is a dynamic looking car, and when you position it alongside major competitors, it is also clearly very elegant. I think it is a more modern car in terms of its proportions, and while for practical packaging reasons the boot and doors are larger, the slimmer glass-to-door ratio results are in a truly contemporary design. It has a lot more of a ‘wedge’ now, starting dynamically at the front and powering toward the back. All the power is on the back wheels, something that has always been the case with Jaguar.”
Still identifiable as an XJ the X350 design moved to a more cab-forward approach, positioning the wheels closer to the corners, incorporating a shorter bonnet and a shallower rake angle for the larger windscreen. The bonnet retained the sculpted shape that was characteristic of the XJ series, with the leading edge and those of the wings wrapping around the shape of the headlights, which, though quite different from the outgoing XJs, had evolved to keep something of the distinctive XJ ‘face’.
Paris Launch 26 September 2002
To highlight the fact that the new Jaguar XJ was an all-alloy structure, two specially commissioned highly-polished examples were manufactured. One example was placed centre-stage for the X350’s debut at the 2002 Paris Motor Show. On 26 September 2002, the seventh generation XJ was unveiled thirty-four years after the original XJ6.
The new model also saw the return of a model with the XJ6 title, this was powered with the 3.0-litre V6 from the S-Type. Otherwise, the XJ was available with the AJV8 in 3.5-litre, 4.2-litre unit and 4.2-litre supercharged configuration. The V8 engines could propel the lightweight XJ to an electronically limited top speed of 155 mph (250 km/hr) with ease; the XJ6 was slightly slower.
When the 2.7-litre V6 diesel was introduced in 2006 the V6 petrol version was soon discontinued; neither V6 petrol nor diesel were available in US markets. The V8 engine was offered in larger 3.5 and 4.2 Litre sizes as well as a supercharged 4.2 Litre. A new six-speed automatic ZF gearbox was fitted which was lighter and offered better economy with lock up on all gears and a larger spread of ratios.
Deliveries of the new XJ commenced during March-April 2003 by which time it had been seen at the Birmingham Motor Show and the Los Angeles and Detroit Motor Shows. At all these shows the polished unpainted XJ was centre-stage; it was even driven through the streets of London and Birmingham to highlight Jaguar’s new build-technology.
Jaguar had built the final X308 as a Daimler and the name slipped from the catalogue; there had been rumours that a dedicated Daimler model that was different from any Jaguar was in the offing but nothing came of this. In its place came a Daimler version of the X350 with the famous fluted radiator grille top, boot plinth and ‘D’ motif in evidence. Inside the walnut veneer had a boxwood inlay, carpets were deeper and lambswool rugs were standard. The high-specification interior had all the features of the LWB models with, as standard, the addition of heated rear seats and a multi-media system that received TV, played DVDs and ran computer games. The 4.2-litre supercharged engine and transmission was unaltered.
Known as the Super-Eight the Daimler was available in a range of colours some of which were exclusive to the model. Though the final car to be built at Browns Lane before its closure was a Jaguar X350 (now with the JDHT), the last X350 to be manufactured at Castle Bromwich – before the line turned to the X358 – was as a Daimler Super Eight (X357) with all extras in the catalogue. By the end of production in 2009, 713 Daimler saloons had been built at Browns Lane and Castle Bromwich.
Development and the End of the Line
The long wheelbase model, introduced in 2005, was the longest vehicle Jaguar had manufactured at the time. With a five inch extension behind the B-pillar, the rear doors were five inches longer, the extended model had a 3,159.8 mm (124.4 in) wheelbase and overall length of 5,214.6 mm (205.3 in). The bodyshell’s weight increased by 24 kg (53 lb) and the roof height increased by 7 mm (0.28 in) over the standard wheelbase XJ.
At the Geneva Motor Show in 2007, Jaguar showed the revised XJ (X358) with, at the front, new grilles and bumper, new side vents, lower side sills, door mirrors with side repeaters, and a small rear spoiler. The car looked far more impressive and different from the older X350. Ian Callum had carried out the facelift which drew cues from his XJ Concept Eight that had been shown in New York in 2004.
Assembly of the XJ was switched from Browns Lane to Castle Bromwich in July 2005 and ceased in 2009 when the last of 83,518 cars built came off the line and went to the Coventry Museum of Transport.
To sum up: the Jaguar X350 XJ may not have been what was expected, as the market had changed since the style clinics enthused about the design. Though profitable, it did not sell in the numbers that Jaguar had predicted, but since its launch in 2002 it has become a much-loved and sought-after model. Those who own the X350 and the X358 (X357 Daimler) relish this quiet and powerful Jaguar which represents excellent value for money and really ought to be sampled by any potential Jaguar enthusiast. They will not be disappointed.
Author: François Prins
Photos: Jaguar Cars & François Prins
© Text and Images – Jaguar Daimler Heritage Trust