A vehicle frame known as its chassis, is the main supporting structure of a motor vehicle, to which all other components are attached, comparable to the skeleton of an organism. Until the 1930s every car had a structural frame, separate from its body; this construction design is known as body-on-frame. Over time, nearly all passenger cars have migrated to unibody construction, meaning their chassis and bodywork have been integrated into one another. Nearly all trucks and most pickups continue to use a separate frame as their chassis; the main functions of a frame in motor vehicles are: To support the vehicle's mechanical components and body To deal with static and dynamic loads, without undue deflection or distortion. These include: Weight of the body and cargo loads. Vertical and torsional twisting transmitted by going over uneven surfaces. Transverse lateral forces caused by road conditions, side wind, steering the vehicle. Torque from the engine and transmission. Longitudinal tensile forces from acceleration, as well as compression from braking.
Sudden impacts from collisions. Types of frame according to the construction: Ladder type frame X-Type frame Off set frame Off set with cross member frame Perimeter Frame Typically the material used to construct vehicle chassis and frames is carbon steel. In the case of a separate chassis, the frame is made up of structural elements called the rails or beams; these are ordinarily made of steel channel sections, made by folding, rolling or pressing steel plate. There are three main designs for these. If the material is folded twice, an open-ended cross-section, either C-shaped or hat-shaped results. "Boxed" frames contain chassis rails that are closed, either by somehow welding them up, or by using premanufactured metal tubing. C-shape By far the most common, the C-channel rail has been used on nearly every type of vehicle at one time or another, it is made by taking a flat piece of steel and rolling both sides over to form a c-shaped beam running the length of the vehicle. Hat Hat frames resemble a "U" and may be either right-side-up or inverted with the open area facing down.
Not used due to weakness and a propensity to rust, however they can be found on 1936–1954 Chevrolet cars and some Studebakers. Abandoned for a while, the hat frame gained popularity again when companies started welding it to the bottom of unibody cars, in effect creating a boxed frame. Boxed Originally, boxed frames were made by welding two matching C-rails together to form a rectangular tube. Modern techniques, use a process similar to making C-rails in that a piece of steel is bent into four sides and welded where both ends meet. In the 1960s, the boxed frames of conventional American cars were spot-welded here and there down the seam. While appearing at first glance as a simple form made of metal, frames encounter great amounts of stress and are built accordingly; the first issue addressed is the height of the vertical side of a frame. The taller the frame, the better it is able to resist vertical flex when force is applied to the top of the frame; this is the reason semi-trucks have taller frame rails than other vehicles instead of just being thicker.
As looks, ride quality, handling became more important to consumers, new shapes were incorporated into frames. The most visible of these are kick-ups. Instead of running straight over both axles, arched frames sit lower—roughly level with their axles—and curve up over the axles and back down on the other side for bumper placement. Kick-ups do the same thing, but don't curve down on the other side, are more common on front ends. Another feature seen are tapered rails that narrow vertically and/or horizontally in front of a vehicle's cabin; this is done on trucks to save weight and increase room for the engine since the front of the vehicle does not bear as much of a load as the back. Design developments include frames. For example, some pickup trucks have a boxed frame in front of the cab, narrower rails underneath the cab, regular C-rails under the bed. On perimeter frames, the areas where the rails connect from front to center and center to rear are weak compared to regular frames, so that section is boxed in, creating what is known as torque boxes.
So named for its resemblance to a ladder, the ladder frame is one of the simplest and oldest of all designs. It consists of two symmetrical beams, rails, or channels running the length of the vehicle, several transverse cross-members connecting them. Seen on all vehicles, the ladder frame was phased out on cars in favor of perimeter frames and unitized body construction, it is now seen on trucks. This design offers good beam resistance because of its continuous rails from front to rear, but poor resistance to torsion or warping if simple, perpendicular cross-members are used; the vehicle's overall height will be greater due to the floor pan sitting above the frame instead of inside it. The term unibody or unit body is short for unitized body, or alternatively unitary construction design, it is A type of body/frame construction in which the body of the vehicle, its floor plan and chassis form a single structure. Such a design is lighter and more rigid than a vehicle having a separate body and frame.
Traditional body-on-frame architecture has shifted to the lighter unitized body structure, now used on most cars. The last UK mass-produced car with a separate chassis was the Triumph Herald
SU carburettors are a brand of carburettor of the constant depression type. The design remained in quantity production for much of the twentieth century; the S. U. Carburetter Company Limited manufactured dual-choke updraught carburettors for aero-engines such as the Rolls-Royce Merlin and Rolls-Royce Griffon. Herbert Skinner, pioneer motorist and an active participant in the development of the petrol engine, invented his Union carburettor in 1904, his much younger brother Carl Skinner a motoring enthusiast, had joined the Farman Automobile Co in London in 1899. He helped Herbert to develop the carburettor. Herbert's son could remember his mother sewing the first leather bellows, it would be given on loan to The Science Museum, South Kensington in 1934. In 1905 Herbert applied for a patent, granted in early 1906. Carl sold his interest in footwear business Lilley & Skinner and became a partner in G Wailes & Co of Euston Road, manufacturers of their carburettor. Herbert continued to develop and patent improvements through to the 1920s including the replacement of the leather bellows by a brass piston though he was a full-time director and divisional manager of Lilley & Skinner.
S. U. Company Limited —Skinner-Union— was incorporated in August 1910 to acquire Herbert's carburettor inventions and it began manufacture of the carburettors in a factory at Prince of Wales Road, Kentish Town in North London. Sales were slow. Following the outbreak of war in 1914 carburettor production nearly stopped with the factory making machine gun parts and some aircraft carburettors. With peace in 1918 production resumed but sales remained slow and the company was not profitable so Carl Skinner approached his customer, W. R. Morris, managed to sell him the business. Carl Skinner became a director of Morris's held empire and remained managing director of S. U. until he retired in 1948 aged 65. Production was moved to the W R Morris owned Wolseley factory at Birmingham. In 1936 W R Morris sold many of his held businesses including S. U. to his listed company, Morris Motors. Manufacture continued, now by The S. U. Carburetter Company Limited, incorporated 15 September 1936 as part of the Morris Organization known as the Nuffield Organization.
The S. U. Carburetter Company Limited of 1936 was voluntarily liquidated in December 1994. In 1996 the name and rights were acquired by Burlen Fuel Systems Limited of Salisbury which incorporated an new company with the name The S. U. Carburetter Company Limited which continues to manufacture carburettors and components for the classic car market. S. U. carburettors were used not only in Morris's Morris and MG products but Rolls-Royce, Rover, Turner, Jaguar and Swedish Volvo, Saab 99 automobiles for much of the twentieth century. S. U. produced carburettors for aircraft engines including the early versions of the Rolls-Royce Merlin, but these were of the conventional fixed-jet updraught type rather than the firm's patented constant-depression design. They remained on production cars through to 1993 in the Mini and the Maestro by which time the company had become part of the Rover Group. Hitachi built carburettors based on the SU design which were used on the Datsun 240Z, Datsun 260Z and other Datsun Cars.
While these appear the same, only their needles are interchangeable. SU carburettors featured a variable venturi controlled by a piston; this piston has a tapered, conical metering rod that fits inside an orifice which admits fuel into the airstream passing through the carburettor. Since the needle is tapered, as it rises and falls it opens and closes the opening in the jet, regulating the passage of fuel, so the movement of the piston controls the amount of fuel delivered, depending on engine demand; the exact dimensions of the taper are tailored during engine development. The flow of air through the venturi creates a reduced static pressure in the venturi; this pressure drop is communicated to the upper side of the piston via an air passage. The underside of the piston is open to atmospheric pressure; the difference in pressure between the two sides of the piston lifts the piston. Opposing this are the weight of the piston and the force of a spring, compressed by the piston rising; because the spring is operating over a small part of its possible range of extension, its force is constant.
Under steady state conditions the upwards and downwards forces on the piston are equal and opposite, the piston does not move. If the airflow into the engine is increased - by opening the throttle plate, or by allowing the engine revs to rise with the throttle plate at a constant setting - the pressure drop in the venturi increases, the pressure above the piston falls, the piston is pushed upwards, increasing the size of the venturi, until the pressure drop in the venturi returns to its nominal level. If the airflow into the engine is reduced, the piston will fall; the result is that the pressure drop in the venturi remains the same regardless of the speed of the airflow - hence the name "constant depression" for carburettors operating on this principle - but the piston rises and falls according to the rate of air delivery. Since the position of the piston controls the position of the needle in the jet and thus the open area of the jet, while the depression in the venturi sucking fuel out of the jet remains constant, the rate of fuel delivery is always a definite function of the rate of air delivery.
The precise nature of the function is determined by the profile of the needle. With appropriate selection of the needle, the fuel delivery can be m
Jaguar is the luxury vehicle brand of Jaguar Land Rover, a British multinational car manufacturer with its headquarters in Whitley, England. Jaguar Cars was the company, responsible for the production of Jaguar cars until its operations were merged with those of Land Rover to form Jaguar Land Rover on 1 January 2013. Jaguar's business was founded as the Swallow Sidecar Company in 1922 making motorcycle sidecars before developing bodies for passenger cars. Under the ownership of S. S. Cars Limited the business extended to complete cars made in association with Standard Motor Co, many bearing Jaguar as a model name; the company's name was changed from S. S. Cars to Jaguar Cars in 1945. A merger with the British Motor Corporation followed in 1966, the resulting enlarged company now being renamed as British Motor Holdings, which in 1968 merged with Leyland Motor Corporation and became British Leyland, itself to be nationalised in 1975. Jaguar was spun off from British Leyland and was listed on the London Stock Exchange in 1984, becoming a constituent of the FTSE 100 Index until it was acquired by Ford in 1990.
Jaguar has, in recent years, manufactured cars for the British Prime Minister, the most recent delivery being an XJ in May 2010. The company holds royal warrants from Queen Elizabeth II and Prince Charles. In 1990 Ford acquired Jaguar Cars and it remained in their ownership, joined in 2000 by Land Rover, till 2008. Ford sold both Jaguar and Land Rover to Tata Motors. Tata created Jaguar Land Rover as a subsidiary holding company. At operating company level, in 2013 Jaguar Cars was merged with Land Rover to form Jaguar Land Rover Limited as the single design, sales company and brand owner for both Jaguar and Land Rover vehicles. Since the Ford ownership era and Land Rover have used joint design facilities in engineering centres at Whitley in Coventry and Gaydon in Warwickshire and Jaguar cars have been assembled in plants at Castle Bromwich and Solihull; the Swallow Sidecar Company was founded in 1922 by two motorcycle enthusiasts, William Lyons and William Walmsley. In 1934 Walmsley elected to sell-out and in order to buy the Swallow business Lyons formed S.
S. Cars Limited, finding new capital by issuing shares to the public. Jaguar first appeared in September 1935 as a model name on an SS 2½-litre sports saloon. A matching open two seater sports model with a 3½-litre engine was named SS Jaguar 100. On 23 March 1945 the S. S. Cars shareholders in general meeting agreed to change the company's name to Jaguar Cars Limited. Said chairman William Lyons "Unlike S. S. the name Jaguar is distinctive and cannot be connected or confused with any similar foreign name."Though five years of pent-up demand ensured plenty of buyers production was hampered by shortage of materials steel, issued to manufacturers until the 1950s by a central planning authority under strict government control. Jaguar sold Motor Panels, a pressed steel body manufacturing company bought in the late 1930s, to steel and components manufacturer Rubery Owen, Jaguar bought from John Black's Standard Motor Company the plant where Standard built Jaguar's six-cylinder engines. From this time Jaguar was dependent for their bodies on external suppliers, in particular independent Pressed Steel and in 1966 that carried them into BMC, BMH and British Leyland.
Jaguar made its name by producing a series of successful eye-catching sports cars, the Jaguar XK120, Jaguar XK140, Jaguar XK150, Jaguar E-Type, all embodying Lyons' mantra of "value for money". The sports cars were successful in international motorsport, a path followed in the 1950s to prove the engineering integrity of the company's products. Jaguar's sales slogan for years was "Grace, Pace", a mantra epitomised by the record sales achieved by the MK VII, IX, Mks I and II saloons and the XJ6. During the time this slogan was used; the core of Bill Lyons' success following WWII was the twin-cam straight six engine, conceived pre-war and realised while engineers at the Coventry plant were dividing their time between fire-watching and designing the new power plant. It had a hemispherical cross-flow cylinder head with valves inclined from the vertical; as fuel octane ratings were low from 1948 onwards, three piston configuration were offered: domed and dished. The main designer, William "Bill" Heynes, assisted by Walter "Wally" Hassan, was determined to develop the Twin OHC unit.
Bill Lyons agreed over misgivings from Hassan. It was risky to take what had been considered a racing or low-volume and cantankerous engine needing constant fettling and apply it to reasonable volume production saloon cars; the subsequent engine was the mainstay powerplant of Jaguar, used in the XK 120, Mk VII Saloon, Mk I and II Saloons and XK 140 and 150. It was employed in the E Type, itself a development from the race winning and Le Mans conquering C and D Type Sports Racing cars refined as the short-lived XKSS, a road-legal D-Type. Few engine types have demonstrated such ubiquity and longevity: Jaguar used the Twin OHC XK Engine, as it came to be known, in the Jaguar XJ6 saloon from 1969 through 1992, employed in a J60 variant as the power plant in such diverse vehicles as the British Army's Combat Vehicle Reconnaissance family of vehicles, as well as the Fox armoured reconnaissance vehicle, the Ferret Scout Car, the Stonefield four-wheel-drive all-terrain lorry. Properly maintained, the standard production XK Engine would a
Rolls-Royce Silver Cloud
The Rolls-Royce Silver Cloud is a luxury automobile produced by Rolls-Royce Limited from April 1955 to March 1966. It was the core model of the Rolls-Royce range during that period; the Silver Cloud was, in turn, replaced by the Silver Shadow. The J. P. Blatchley design was a major change from the pre-war models and the derivative Silver Dawn; as part of a range rationalisation the Bentley S1 is similar, apart from its radiator grille. Construction was body-on-frame, which permitted special bodied versions, though the overwhelming majority were built with the standard Pressed Steel Company manufactured steel body shell. A light-weight aluminium-based alloy was used for bonnet/hood and boot/trunk lid; the chassis was a simple steel box section, welded together and rigid. The car was 5.38 m long, 1.90 m wide, massed 1.95 tonnes. The engine was a 155 hp / 4000 rpm 4.9 L six-cylinder unit with inlet over exhaust valves: twin SU carburettors were added in September 1957. The standard transmission was a four-speed automatic, the General Motors sourced Hydramatic transmission.
The turning circle was 41 feet 8 inches. Brakes were hydraulic and assisted by the Rolls-Royce mechanical servo with 11 in drums and suspension was independent coils at the front and semi-elliptic springs at the rear. Twin brake master cylinders were incorporated from April 1956. Power steering and air conditioning became available as options in 1956. A long-wheelbase version lengthened by 4 in was made available in September 1957, outwardly similar to the existing car but offering improved leg space for rear-seat passengers; the British Motor magazine tested a standard-wheelbase factory-bodied Series I in 1956 recording a top speed of 102.9 mph and acceleration from 0-60 mph in 13.5 seconds and a fuel consumption of 14.5 miles per imperial gallon. The test car cost £5078 including taxes; the Silver Cloud II was introduced in 1959. It was little changed externally, but was given a new Rolls-Royce developed 6.2 L V8 engine, which pushed the weight to 2.11 tonnes. Performance was improved and top speed was raised to 183 km/h, but the main improvements were in acceleration and torque.
Power steering became standard. Electrically operated windows were now available as an option. Although the improved performance of the new car was welcomed, commentators of the time noted that the V8-engined Silver Cloud II was neither as quiet nor as smooth as the straight-six-cylinder-engined Silver Cloud I, despite the new engine's hydraulic tappet operation; the new wet-linered V8 was a little cramped in an engine bay intended for a narrower unit: in order to change the spark plugs it was necessary to remove the front wheel on the car's right side. There seems to have been a problem with crankshaft breakages in the earlier V8s: this was blamed on lack of lubrication to the bearings; the basic architecture of the Silver Cloud II did not change between 1959 and 1963, but there were numerous minor changes implemented, notable among them a succession of improvements to the ventilation system. Interior changes in 1961 included the adoption of blue instrument lighting, the introduction of a combined indicator / headlamp flasher switch and of a handbrake warning light.
A remodelled rear light assembly was introduced in May 1962 and a change to single sealed-beam headlamps was made in August 1962. The Motor magazine tested a Series II in 1960, they recorded a top speed of 104.7 mph, acceleration from 0-60 mph in 10.9 seconds and a fuel consumption of 13 miles per imperial gallon. The test car cost £6092 including taxes; the Silver Cloud III was first displayed to the public at the Paris salon at the beginning of October 1962 but along with the Bentley S3 the cars were displayed on a specialist coachwork stand as if the modifications were to the special order of a particular customer. External dimensions were altered, the interior remodelled, the weight reduced by a little over 100 kg and improvements made to the engine which included fitting 2-inch SU carburettors in place of the 1¾ inch units used on the Series II Silver Cloud; the compression ratio was increased to 9:1, reflecting the higher octane levels of premium fuel in major markets, although the option of a lower 8:1 compression ratio was still offered in markets where non-availability of higher octane fuels might be an issue.
Rolls-Royce, as before, refused to disclose overall engine power output, but indicated that there had been an improvement of "perhaps 7%". Increased power and weight reduction boosted performance slightly; the engine now included a nitride hardened crankshaft to reflect the extra power being generated and in response to reports of broken crankshafts in the earlier V8 Silver Clouds. The transmission was a GM Hydramatic; the headlights were grouped in a four-headlamp layout subsequently continued in the Silver Shadow. Other external changes included a increased slope of the bonnet to correspond with a 1 1⁄2 inches reduction in radiator grille height. Between 1963 and 1966 there were no major changes. Stainless steel wheel trims replaced chrome-plated ones in April 1963, an improved rear window demister was introduced in November of the same year. Wider front seats were fitted in January 1964, five months a revised headlamp surround now incorporated a small RR monogram. A chrome badge reading "Silver Cloud III" in an italic font can be seen on the right bottom side of the boot of most UK and European delivered examples, whilst US versions were delivered without this badge.
As with earlier models, Roll
Overdrive is the operation of an automobile cruising at sustained speed with reduced engine revolutions per minute, leading to better fuel consumption, lower noise, lower wear. Use of the term is confused, as it is applied to several related, meanings; the most fundamental meaning is that of an overall gear ratio between engine and wheels, such that the car is over-geared, cannot reach its potential top speed, i.e. the car could travel faster if it were in a lower gear, with the engine turning at higher RPM. The purpose of such a gear may not be obvious; the power produced by an engine increases with the engine's RPM to a maximum falls away. The point of maximum power is somewhat lower than the absolute maximum RPM to which the engine is limited, the "redline" RPM. A car's speed is limited by the power required to drive it against air resistance, which increases with speed. At the maximum possible speed, the engine is running at its point of maximum power, or power peak, the car is traveling at the speed where air resistance equals that maximum power.
There is therefore one specific gear ratio at which the car can achieve its maximum speed: the one that matches that engine speed with that travel speed. At travel speeds below this maximum, there is a range of gear ratios that can match engine power to air resistance, the most fuel efficient is the one that results in the lowest engine speed. Therefore, a car needs one gearing to reach maximum speed but another to reach maximum fuel efficiency at a lower speed. With the early development of cars and the universal rear-wheel drive layout, the final drive ratio for fast cars was chosen to give the ratio for maximum speed; the gearbox was designed so that, for efficiency, the fastest ratio would be a "direct-drive" or "straight-through" 1:1 ratio, avoiding frictional losses in the gears. Achieving an overdriven ratio for cruising thus required a gearbox ratio higher than this, i.e. the gearbox output shaft rotating faster than the engine. The propeller shaft linking gearbox and rear axle is thus overdriven, a transmission capable of doing this became termed an "overdrive" transmission.
The device for achieving an overdrive transmission was a small separate gearbox, attached to the rear of the main gearbox and controlled by its own shift lever. These were optional on some models of the same car; as popular cars became faster relative to legal limits and fuel costs became more important after the 1973 oil crisis, the use of 5-speed gearboxes became more common in mass-market cars. These had a direct fourth gear with an overdrive 5th gear, replacing the need for the separate overdrive gearbox. With the popularity of front wheel drive cars, the separate gearbox and final drive have merged into a single transaxle. There is no longer a propeller shaft and so one meaning of "overdrive" can no longer be applied; however the fundamental meaning, that of an overall ratio higher than the ratio for maximum speed, still applies. Although the deliberate labelling of an overdrive is now rare, the underlying feature is now found across all cars; the power needed to propel a car at any given set of conditions and speed is straightforward to calculate, based on the total weight and the vehicle's speed.
These produce two primary forces slowing the car: air drag. The former varies with the speed of the vehicle, while the latter varies with the square of the speed. Calculating these from first principles is difficult due to a variety of real-world factors, so this is measured directly in wind tunnels and similar systems; the power produced by an engine increases with the engine's RPM to a maximum falls away. This is known as the point of maximum power. Given a curve describing the overall drag on the vehicle, it is simple to find the speed at which the total drag forces are the same as the maximum power of the engine; this defines the maximum speed. The rotational speed of the wheels for that given forward speed is simple to calculate, it is the tire circumference multiplied by the RPM; as the tire RPM at maximum speed is not the same as the engine RPM at that power, a transmission is used with a gear ratio to convert one to the other. At slightly lower speeds than maximum, the total drag on the vehicle is less, the engine needs to deliver this reduced amount of power.
In this case the RPM of the engine has changed while the RPM of the wheels has changed little. This condition calls for a different gear ratio. If one is not supplied, the engine is forced to run at a higher RPM than optimal; as the engine requires more power to overcome internal friction at higher RPM, this means more fuel is used to keep the engine running at this speed. Every cycle of the engine leads to wear, so keeping the engine at higher RPM is unfavorable for engine life. Additionally, the sound of an engine is related to the RPM, so running at lower RPM is quieter. If one runs the same RPM transmission exercise outlined above for maximum speed, but instead sets the "maximum speed" to that of highway cruising, the output is a higher gear ratio that provides ideal fuel mileage. In an era when cars were not able to travel fast, the maximum power point might be near enough to the desired speed that additional gears were not needed, but as more powerful cars appeared during the 1960s, this disparity between the maximum power point and desired speed grew considerably.
This meant that cars were operating far from their most efficient point. As the desire for better fuel economy grew after the 1973 oil crisis, the need for a "cruising gear" became more pressing. Th
Jaguar XJ is a series of full-size luxury cars produced under the Jaguar marque by British motor car manufacturer Jaguar Cars since 1968 across four basic platform generations with various updated derivatives of each. 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, 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 original first-generation XJ ran for a total of 24 years, with two major facelifts in 1973 and 1979. Retrospectively these are known as "Series" XJs among the Jaguar enthusiast community; the XJ6, using 2.8-litre and 4.2-litre 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. An upmarket version was marketed under the Daimler brand as the Daimler Sovereign, continuing the name from the Daimler version of the Jaguar 420; 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, 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 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 enabled performance oriented drivers to hold lower ratios at higher revs to achieve better acceleration. "Greatly improved shift quality" was 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. 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, powered by a 5.3 L V12 engine. The car as presented at that time was the world's only mass-produced 12-cylinder four-door car, with a top speed "around 140 mph" 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, providing adequate cooling had evidently been a challenge for the engineers designing the installation. Bonnet/hood louvres such as those fitted on the 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 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, benefited from its own thermostatically controlled cooling fan. 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. 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 and the 5.3 L V12 XJ12 were continued with an addition of a 3.4 L version of the XK engine available from 1975. 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 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 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 effective Series I system. In April 1975, the North American Series II got a revised set of front bumpers
A luxury vehicle is intended to provide passengers with increased comfort, a higher level of equipment and increased perception of quality than regular cars for an increased price. The term is subjective and can be based on either the qualities of the car itself or the brand image of its manufacturer. Luxury brands are considered to have a higher status than premium brands, however there is no fixed differentiation between the two. Traditionally, luxury cars have been large vehicles, however contemporary luxury cars range in size from compact cars to large sedans and SUVs; some car manufacturers market their luxury models using the same marque as the rest of their models. Other manufacturers market their luxury models separately under a different marque, for example Lexus and Bentley. A luxury car is sold under a mainstream marque and is re-branded under a specific luxury marque. For mass-produced luxury cars, sharing of platforms or components with other models is common, as per modern automotive industry practice.
Several car classification schemes which include a luxury category, such as: Australia: Since the year 2000, the Federal Government's luxury car tax applies to new vehicles over a certain purchase price, with higher thresholds applying for cars considered as fuel efficient. As of 2019, the thresholds were AU$66,000 for normal cars and AU$76,000 for fuel efficient cars. Europe: Luxury cars are classified as F-segment vehicles in the European Commission classification scheme. France: The term "voiture de luxe" is used for luxury cars. Germany: The term German: Oberklasse is used for luxury cars. Russia: The term (автомобиль представительского класса is used for luxury cars. Rental cars: The ACRISS Car Classification Code is a system used by many car rental companies to define equivalent vehicles across brands; this system includes "Luxury" and "Luxury Elite" categories. The criteria for a vehicle to be considered "luxury" is not published; the premium compact class is the smallest category of luxury cars.
It became popular in the mid-2000s, when European manufacturers— such as Audi, BMW and Mercedes-Benz— introduced new entry level models that were smaller and cheaper than their compact executive models. Examples include the Alfa Romeo Giulietta, Audi A3, Buick Verano, BMW 1 Series, Lexus CT 200h, Infiniti Q30, Mercedes-Benz A-Class, Mercedes-Benz B-Class, Volvo C30, Volvo V40, BMW i3. Premium compacts compete with well-equipped mid-size cars, optioned premium compact cars can have pricing and features that operlaps with compact executive cars. A compact executive car is a premium car smaller than an executive car. In European classification, compact executive cars are part of the D-segment. In North American terms, close equivalents are "compact premium car", "compact luxury car", "entry-level luxury car" and "near-luxury car". Executive car is a British term for an automobile larger than a large family car. In official use, the term is adopted by Euro NCAP, a European organization founded to test for car safety.
It is a passenger car classification defined by the European Commission. The next category of luxury cars is known in Great Britain as a luxury saloon or luxury limousine, is known in the United States as a full-size luxury sedan or large luxury sedan, it is the equivalent of the European German Oberklasse segment. Many of these luxury saloons are the flagship for the marque and therefore include the newest automotive technology. Several models are available in long-wheelbase versions, which provide additional rear legroom and a higher level of standard features. Examples of luxury saloons / full-size luxury sedans include the BMW 7 Series, Cadillac CT6 Genesis G90, Mercedes-Benz S-Class, Lexus LS, Porsche Panamera. Luxury cars costing over US$100,000 can be considered as "ultra-luxury cars". Examples include Maybach 57 and Bentley Arnage. Exotic cars which are targeted towards performance rather than luxury are not classified as ultra-luxury cars when their cost is greater than US$100,000. Several entry-level models from low-volume luxury car manufacturers, such as the Bentley Continental GT and the Rolls-Royce Ghost have been described as "entry-opulent" cars.
Many ultra-luxury cars are produced by brands with a long history of manufacturing luxury cars. The history of a brand and the exclusivity of a particular model can result in price premiums compared to luxury cars with similar features from less prestigious manufacturers. V12 engines are common in ultra-luxury cars. Long before the luxury SUV segment became popular in the 1990s, the vehicle in this segment was the 1966 Jeep Super Wagoneer, marketed at the time as a station wagon, it was the first off-road SUV to offer a V8 engine, automatic transmission, luxury car trim and equipment. Standard equipment included bucket seating, a center console, air conditioning, seven-position tilt steering wheel, a vinyl roof and gold colored trim panels on the body sides and tailgate. By the late 1970s, optional equipment included an electric sunroof, The 1978 Jeep Wagoneer Limited was the spiritual successor to the Super Wagoneer and was the first four-wheel drive car to use leather upholstery. Another precursor to the luxury SUV is the Range Rover, released in 1970.
It was the first road-going vehicle to have a permanent four-wheel drive system, split