The Jaguar XJ is the name of a series of full-size luxury cars sold by the British automobile brand, Jaguar Cars since 1968. Since 1970 they have been Jaguar's flagship. The original model was the last Jaguar saloon to have had the input of Sir William Lyons, the company's founder, and the model has been featured in countless media and high-profile appearances. The current Jaguar XJ was launched in 2009. It is one of the cars used by the British royal family and an armoured version is used for transporting the UK Prime Minister.
The XJ6, using 2.8-litre (2,792 cc or 170.4 cu in) and 4.2-litre (4,235 cc or 258.4 cu in) straight-six cylinder versions of Jaguar's renowned XK engine, replaced most of Jaguar's saloons – which, in the 1960s, had expanded to four separate ranges. Apart from the engines, other main assemblies carried over from previous models were the widest version of Jaguar's IRS unit from the Mark X and the subframe mounted independent front suspension first seen in the 1955 2.4-litre with new anti-dive geometry.
The car was introduced in September 1968. Power-assisted steering and leather upholstery were standard on the 2.8 L De Luxe and 4.2 L models and air conditioning was offered as an optional extra on the 4.2 L. Daimler versions were launched in October 1969, in a series of television advertisements featuring Sir William. In these spots, he referred to the car as "the finest Jaguar ever". An unusual feature, inherited from the Mark X and S-Type saloons, was the provision of twin fuel tanks, positioned on each side of the boot / trunk, and filled using two separately lockable filler caps: one on the top of each wing above the rear wheel arches. Preliminary reviews of the car were favourable, noting the effective brakes and good ride quality.
In March 1970 it was announced that the Borg-Warner Model 8 automatic transmission, which the XJ6 had featured since 1968, would be replaced on the 4.2-litre-engined XJ6 with a Borg-Warner Model 12 unit. The new transmission now had three different forward positions accessed via the selector lever, which effectively enabled performance oriented drivers to hold lower ratios at higher revs to achieve better acceleration. "Greatly improved shift quality" was also claimed for the new system.
Around this time minor changes were made as well, such as moving the rear reflectors from beside to below the rear lights; on the interior the chrome gauge bezels were changed for black ones, to cut down on distracting reflections.
In 1972 the option of a long-wheelbase version, providing a 4" increase in leg room for passengers in the back, became available.
The XJ12 version was announced in July 1972, featuring simplified grille treatment, and powered by a 5.3 L V12 engine (coupled to a Borg Warner Model 12). The car as presented at that time was the world's only mass-produced 12-cylinder four-door car, and, with a top speed "around 140 mph" (225 km/h) as the "fastest full four-seater available in the world today". Although it had been the manufacturer's intention from launch that the XJ would take the twelve-cylinder engine, its installation was nonetheless a tight fit, and providing adequate cooling had evidently been a challenge for the engineers designing the installation. Bonnet/hood louvres such as those fitted on the recently introduced twelve-cylinder E Type were rejected, but the XJ12 featured a complex "cross-flow" radiator divided into two separated horizontal sections and supported with coolant feeder tanks at each end: the engine fan was geared to rotate at 1¼ times the speed of the engine rpm, subject to a limiter which cut in at a (fan) speed of 1,700 rpm. The fuel system incorporated a relief valve that returned fuel to the tank when pressure in the leads to the carburetters exceeded 1.5 psi to reduce the risk of vapour locks occurring at the engine's high operating temperature, while the car's battery, unusually, benefited from its own thermostatically controlled cooling fan.
The Jaguar XJ12, launched during the summer of 1972, featured a simplified grille.
3,235 of these first generation XJ12s were built. A badge-engineered version, the Daimler Double-Six, was introduced in 1972, reviving the Daimler model name of 1926–1938.
Commonly referred to as the "Series II", the XJ line was facelifted in autumn 1973 for the 1974 model year. The 4.2 L I-6 XJ6 (most popular in the United Kingdom) and the 5.3 L V12 XJ12 were continued with an addition of a 3.4 L (3,442 cc or 210.0 cu in) version of the XK engine available from 1975.
The Series II models were known for their poor build quality, which was attributed to Jaguar being part of the British Leyland group along with massive labour union relations problems that plagued most of industrial England in the same time period, and to problems inherent in the design of certain Lucas-sourced components.
Initially the Series II was offered with two wheelbases, but at the 1974 London Motor Show Jaguar announced the withdrawal of the standard wheelbase version: subsequent saloons/sedans all featured the extra 4 inches (10 cm) of passenger cabin length hitherto featured only on the long-wheelbase model. By this time the first customer deliveries of the two-door coupe, which retained the shorter standard-wheelbase (and which had already been formally launched more than a year earlier) were only months away.
Visually, Series II cars are differentiated from their predecessors by raised front bumpers to meet US crash safety regulations, which necessitated a smaller grille, complemented by a discreet additional inlet directly below the bumper. The interior received a substantial update, including simplified heating and a/c systems to address criticisms of the complex and not very effective Series I system.
In April 1975, the North American Series II got a slightly revised set of front bumpers which had rubber over-riders covering the full length of the bumper with embedded turn signals at each end. In 1975 V12 XJS / XJ12L cars and in 1978 the 4.2 6 cyl. XJ6L North American cars got the addition of Bosch-Lucas electronic fuel injection in the place of Zenith-Stromberg carburettors.
In May 1977, it was announced that automatic transmission version of the 12-cylinder cars would be fitted with a General Motors three-speed THM 400 transmission in place of the British-built Borg-Warner units used hitherto.
The 1978 UK model range included the Jaguar XJ 3.4, XJ 4.2, XJ 5.3, Daimler Sovereign 4.2, Double-Six 5.3, Daimler Vanden Plas 4.2, Double-Six Vanden Plas 5.3.
In New Zealand, knock-down kits of the Series II were assembled locally by the New Zealand Motor Corporation (NZMC) at their Nelson plant. In the last year of production in New Zealand (1978), a special 'SuperJag' (XJ6-SLE) model was produced which featured half leather, half dralon wide pleat seats, vinyl roof, chrome steel wheels and air conditioning as standard. New Zealand produced models featured speedometers in km/h, and the black vinyl mats sewn onto the carpets in the front footwells featured the British Leyland 'L' logo.
Though worldwide production of the Series II ended in 1979, a number were produced in Cape Town, South Africa until 1981.
A total of 91,227 Series II models were produced, 14,226 of them with the V12 engine.
A 9,378-car run of two-door XJ coupés with a pillarless hardtop body called the XJ-C was built between 1975 and 1978. The car was actually launched at the London Motor Show in October 1973, but it subsequently became clear that it was not ready for production, and the economic troubles unfolding in the western world at this time seem to have reduced further any sense of urgency about producing and selling the cars: it was reported[where?] that problems with window sealing delayed production. XJ coupés finally started to emerge from Jaguar show-rooms only some two years later. The coupé was based on the short-wheelbase version of the XJ. The coupé's elongated doors were made out of a lengthened standard XJ front door (the weld seams are clearly visible under the interior panels where two front door shells were grafted together with a single outer skin). A few XJ-Cs were modified by Lynx Cars and Avon into convertibles with a retractable canvas top, but this was not a factory product. Lynx conversions (16 in total) did benefit of powered tops. Both six and twelve-cylinder models were offered, 6,505 of the former and 1,873 of the latter. Even with the delay, these cars suffered from water leaks and wind noise. The delayed introduction, the labour-intensive work required by the modified saloon body, the higher price than the four-door car, and the early demise promulgated by the new XJ-S, all ensured a small production run.
All coupes came with a vinyl roof as standard. Since the coupe lacked B-pillars, the roof flexed enough that the paint used by Jaguar at the time would develop cracks. More modern paints do not suffer such problems, so whenever a coupe is repainted it is viable to remove the vinyl. Today many XJ-Cs no longer have their vinyl roof, also removing the threat of roof rust. Some owners also modified their XJ-C by changing to Series III bumpers. This lifted the front indicators from under the bumper and provided built in rear fog lights.
A small number of Daimler versions of the XJ-C were made. One prototype Daimler Vanden Plas version XJ-C was also made, however this version never went into production.
From April 1979, the XJ was facelifted again, and was known as the "Series III."
Using the long-wheelbase version of the car, the XJ6 incorporated a subtle redesign by Pininfarina.
Externally, the most obvious changes over the SII were the thicker and more incorporated rubber bumpers with decorative chrome only on the top edge, flush door handles for increased safety, a one-piece front door glass without a separate 1/4 light, a grille with only vertical vanes, reverse lights moved from the boot plinth to the larger rear light clusters and a revised roofline with narrower door frames and increased glass area.
There were three engine variants, including the 5.3 L V12, the 4.2 L straight-six and 3.4 L straight-six. The larger six-cylinder, and V12 models incorporated Boschfuel injection (made under licence by Lucas) while the smaller six-cylinder was carbureted. The smaller 3.4 L six-cylinder engine was not offered in the US
The short-wheelbase saloon and coupé had been dropped during the final years of the Series II XJ. The introduction of the Series III model also saw the option of a sunroof and cruise control for the first time on an XJ model.
The 1979 UK model range included the Jaguar XJ6 3.4 & 4.2, XJ12 5.3, Daimler Sovereign 4.2 & Double-Six 5.3 and Daimler Vanden Plas 4.2 & Double-Six Vanden Plas 5.3.
In 1981 the 5.3 V12 models received the new Michael May designed "fireball" high compression cylinder head engines and were badged from this time onwards to 1985 as HE (High Efficiency) models.
In late 1981 Daimler Sovereign and Double Six models received a minor interior upgrade for the 1982 model year with features similar to Vanden Plas models. Also for the 1982 model year, a top spec "Jaguar" Vanden Plas model was introduced for the US market - a model designation still used today.
In late 1982 the interior of all Series III models underwent a minor update for the 1983 model year. A trip computer appeared for the first time and was fitted as standard on V12 models. A new and much sought-after alloy wheel featuring numerous distinctive circular holes was also introduced, commonly known as the "pepperpot" wheel.
In late 1983 revision and changes were made across the Series III model range for the 1984 model year, with the Sovereign name being transferred from Daimler to a new top spec Jaguar model, the "Jaguar Sovereign". A base spec Jaguar XJ12 was no longer available, with the V12 engine only being offered as a Jaguar Sovereign HE or Daimler Double Six. The Vanden Plas name was also dropped at this time in the UK market, due to Jaguar being sold by BL and the designation being used on top-of-the-range Rover-branded cars in the home UK market. Daimler models became the Daimler 4.2 and Double Six and were the most luxurious XJ Series III models, being fully optioned with Vanden Plas spec interiors.
The 1984 UK model range included the Jaguar XJ6 3.4 & 4.2, Sovereign 4.2 & 5.3, Daimler 4.2 & Double Six 5.3.
Production of the Series III XJ6 continued until early 1987 and on till 1992 with the V12 engine. In 1992, the last 100 cars built were numbered and sold as part of a special series commemorating the end of production for Canada. These 100 cars featured the option of having a brass plaque located in the cabin. It was the original purchaser's option to have this plaque, which also gave a number to the car (such as No. 5 of 100, etc.), fitted to the glove box, to the console woodwork or not fitted at all. This brass plaque initiative did not come from Jaguar in Coventry. It was a local effort, by Jaguar Canada staff and the brass plaques were engraved locally.
132,952 Series III cars were built, 10,500 with the V12 engine. In total between 1968 and 1992 there were around 318,000 XJ6 and XJ12 Jaguars produced.
The intended replacement for the Series XJ was code-named XJ40, and development on the all-new car began in the early 1970s (with small scale models being built as early as 1972.) The project suffered a number of delays due to problems at parent company British Leyland and events such as the 1973 oil crisis. The XJ40 was finally introduced in 1986 at the British International Motor Show.
With the XJ40, Jaguar began to place more emphasis on build quality as well as simplification of the XJ's build process. With 25 per cent fewer body panel pressings required versus the Series XJ, the new process also saved weight, increased the stiffness of the chassis, and reduced cabin noise.
The new platform came with significantly different styling, which was more squared-off and angular than the outgoing Series III. Individual round headlamps were replaced with rectangular units on the higher-specification cars, and all models came with only a single, wide-sweeping windshield wiper. The interior received several modernisations such as the switch to a digital instrument cluster (although this was eventually discontinued for MY 1990 in favour of analogue instruments.)
The six-cylinder XJ40s are powered by the AJ6 inline-six engine, which replaced the XK6 unit used in earlier XJs. The new unit featured a four-valve, twin overhead cam design. In 1993, one year before XJ40 production ended, the V12-powered XJ12 and Daimler Double Six models were reintroduced.
The X300, introduced in 1994, was stylistically intended to evoke the image of the more curvaceous Series XJ. The front of the car was redesigned significantly to return to four individual round headlamps that provided definition to the sculptured bonnet. Mechanically, it was similar to the XJ40 that it replaced.
Six-cylinder X300s are powered by the AJ16 inline-six engine, which is a further enhancement of the AJ6 engine that uses an electronic distributorless ignition system. The V12 remained available until the end of the X300 production in 1997 (although it ended one year earlier in the United States market due to problems meeting OBD-II-related emissions requirements.)
Jaguar first introduced the supercharged XJR in X300 production; the first supercharged road car manufactured by the company.
With the introduction of the X308 generation in 1997 came a switch from the XJ6 and XJ12 nomenclature to XJ8, reflecting the fact that the X308 cars were powered by a new V8 engine.
The exterior styling of the X308 was similar to the X300 with minor refinements such as a change to oval indicator lenses and amber style round fog lights. The interior was also updated to eliminate the instrument binnacle used on the X300; instead, three large gauges were set into recesses in the walnut-faced dashboard in front of the driver.
The major mechanical change was the replacement of both the inline-six and V12 engines with new eight-cylinder AJ-V8 in either 3.2 L or 4.0 L versions, with the 4.0 L also available in supercharged form in the XJR (A sport oriented model). No manual transmission was available, and all X308 models were supplied with a five-speed automatic gearbox.
X350 and X358 (2003–2009)
XJ8, Vanden Plas, XJR & Super V8
Daimler Super Eight
Jaguar introduced the re-engineered third generation XJ (known as X350) in 2003, featuring an all-aluminium body. The new car also featured a V8 engine, an XJ8 badge as well as greater interior and luggage space.
The V8 engine was offered in larger 3.5 and 4.2-litre sizes as well as a supercharged 4.2-litre. The car's lighter weight meant the 3.0-litre V6 was also offered, although with the later introduction of the 2.7-litre V6 diesel the V6 petrol version was discontinued (neither V6 petrol nor diesel were available in US markets). A new six-speed automatic gearbox was fitted which was lighter and offered better economy with lock-up on all gears and a larger spread of ratios.
Air suspension was fitted all round which provided adaptive damping as well as rear self leveling. Unlike other manufacturers Jaguar did not provide any driver control of ride height or suspension mode which was fully computer controlled. Dynamic stability control as well as traction control were standard.
Two-zone climate control was also standard, with four-zone available on long-wheelbase models. An optional touch screen interface controlled default settings, satellite navigation, the Alpine audio system, and bluetooth telephone. "Jaguar Voice" offered voice control of many functions.
In keeping with Ian Callum's new design direction for Jaguar, it is an all-new exterior design and a break from the XJ series mould carried over on all previous generations. It is a longer, wider car that looks much bigger than its predecessor. The front has clear links with the executive car XF, although with slimmer, sleeker lights and a larger, squarer grille and more aggressive appearance. The rear is the contentious part, like nothing Jaguar has shown before. The upright, swooping taillights, nicknamed "cat's claws", and black roof panels each side of the rear screen, which aim to hide the XJ's width, are the most striking aspects. There is also a standard full-length sunroof, that extends all the way back with just a single body-coloured roof panel that the designer likens to bridges on yachts.
The new XJ features an innovative, all-LCD dashboard and console displays. The dashboard can be configured to display various virtual dials in addition to the obligatory speedometer. The console display presents different views to the driver and passenger, including control of a sophisticated video and audio system.
Like several of its predecessors, the X351 is available in both standard and long-wheelbase form, as well as many special editions. Engines are modern units already seen in other JLR products: the 5-litre petrol V8 either normally aspirated or supercharged, or a twin-turbo 3-litre diesel that is predicted to account for most of the sales. For 2013 a 3-litre supercharged V6 was introduced to the line-up, primarily as an alternative to the diesel unit for improved fuel economy.
The X351 received a minor facelift in 2014, primarily upgrading the suspension and rear seat facilities on the long wheelbase versions, but also introducing small cosmetic changes across the range, and making stop-start technology standard on all engines.
The X351 received another facelift in 2015, adding LED headlights, J-Blade rear taillights, and adding several new driver assistance and safety features such as lane assist, adaptive cruise control with a new feature known as "Queue assist", reverse traffic direction, closing vehicle sensing, a 360 degree camera system, and semi-automated parking features 
Just prior to World War II, Jaguar, known then as SS Cars, started using a numbering system beginning with the letter X for internal projects. X meaning experimental, XB for military chassis projects and XF to XK for engines. This numbering system has never been consistent and there appear to be many omissions and duplications.