(continued)
Also like the XK it replaces, the all-new XK will be available in both two-door
Coupe and Convertible forms, each model in its own right developed in parallel
under one umbrella program. The decision to give the Convertible version a
classic soft-top rather than a folding hard-top means the open option offers
exactly the same 2+2 seating layout, without compromising the elegant lines of
the rear body, the strong, rising waistline or the light weight of the car.
The new XK was created by Jaguar’s new design team under the leadership of
Design Director Ian Callum, to push Jaguar deeper into the 21 st century. The
new XK’s lines are bold and beautiful, powerful but elegant. In Ian Callum’s
words, it looks “just like a Jaguar should – powerful and exciting. That power
comes from a sense of tension, muscle and form and is very much part of the new
design language we are creating.”
That new language begins with the proportions and stance, which are dramatically
different from those of the previous XK. The new car sits on a longer wheelbase
but it has markedly shorter overhangs, so it is very little longer overall. Its
width, strong, high waistline and short, powerful haunches give an impression of
a car hugging the ground, crouched, ready for action. With its dynamic hood and
roof lines it looks much more compact, more contemporary, and extremely muscular
and athletic - suggesting movement, power and agility even when it is
stationary.
Although the new XK looks very compact, it has excellent luggage space, and the
Coupe is designed to be able to carry two golf bags. Although the rear overhang
is fully 4.8 inches shorter than on the previous XK, the rear luggage volume is
only 0.28 cu. ft. less, or 0.78 cu. ft. more when the optional runflat tires are
specified – and of course it has gained the enormous benefit of the all-new
Liftback design, which provides excellent access to the loadspace area.
“I am very proud of the new XK,” says Ian Callum. “It is contemporary with
wonderful modern proportions yet we have succeeded in integrating design cues
from our heritage. The front grille, for example, is pure E-type, and makes the
perfect statement that this is, first and foremost, a Jaguar.”
The Engine
A key element in the character of a sports car is its engine. The new XK will be
launched with a powerful four-cam naturally aspirated 4.2-liter AJ-V8
powerplant. This compact, lightweight engine is based on that fitted to the
latest generation XJ saloon and has undergone significant development compared
with the engine used in the previous XK, including new fuel-injection
technology. The latest 4.2-liter engine satisfies stringent US ULEV II emissions
regulations.
The naturally aspirated 4.2-liter V8 engine produces 300
bhp and develops maximum torque of 303 lb-ft at 4,100
rpm. Again, the spread of torque is an important ingredient in the XK’s
effortlessly sporty character, and this engine delivers more than 85 percent of
torque all the way from 2,000 to 6,000 rpm. Yet it still
offers fine fuel economy and low emissions figures, with a drop in CO2 emissions
of five percent.
The naturally aspirated 4.2-liter V8 XK Coupe has an electronically limited
maximum speed of 155 mph (250 km/h) and a 0-60
mph time of 5.9 seconds, plus instant throttle response and broad
flexibility for punchy performance across the range. With the new XK’s weight
savings, the new naturally aspirated 4.2’s standing quarter-mile time of 14.4
seconds is less than half a second off the pace of the previous supercharged 4.2
XKR.
The latest AJ-V8 engine was developed to satisfy ULEV II, as well as strict
European emissions requirements. That means a 50 percent reduction in
hydrocarbons (HC) and oxides of nitrogen (NOx) and a 60 percent reduction in
carbon monoxide (CO) 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 compact AJ-V8 engine has very stiff but lightweight all-aluminum
construction, with eight cylinders in a 90-degree ‘V’. The combination of
strength and lightness begins with a ribbed cylinder block and cylinder heads.
The 4.2-liter version has bore and stroke of 3.39 x 3.56 inches for a capacity
of 4196cc. The fully balanced four-throw, six-counterweight crankshaft is
supported in five main bearings. The connecting rods use split-fractured big-end
journals for strength with light weight and perfect balance. Each cylinder head
carries two chain-driven overhead camshafts, which are hollow, to save weight
and improve performance by allowing higher engine speeds. The camshafts operate
four valves (two inlet and two exhaust) in each pentroof combustion chamber,
around a central spark plug. An unusually narrow 28 degree included valve angle
allows a compact combustion chamber shape and narrower heads, which benefits
overall packaging.
Equally important for its new role in Jaguar’s sportiest cars, the 4.2-liter
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.
Transmission
The XK uses the latest version of Jaguar’s class-leading six-speed epicyclic
automatic transmission, which is widely regarded as one of the best automatic
transmissions in the premium, sports car market. It features Bosch Mechatronic
shift – an electro-hydraulic shift mechanism whose adaptive shift strategy
responds to both road conditions and driving style, to give the smoothest shifts
with optimum performance.
The XK’s transmission introduces a new generation of automatic gearshift for
Jaguar, replacing the familiar ‘J’ gate with the Jaguar Sequential Shift system
with Park, Reverse, Neutral, Drive and Sport modes. The fully automatic Drive
mode adapts to individual driving styles, while a Sport Auto mode can also be
selected. This offers an even more responsive fully automatic shift strategy.
For the first time in a Jaguar, drivers will be able to use steering
wheel-mounted paddles to change gears. In either Drive or Sport modes instant
access to manual operation is achieved via the shift paddles. In manual mode,
the transmission controller uses an alternative parameter set to control gear
shifts, enabling delivery of extremely rapid and responsive manual shifts,
whilst maintaining class-leading Jaguar shift quality in automatic modes.
Interaction with the torque-based engine management system allows for precise
torque control during shifts – engine inertia is used to enhance acceleration
during upshifts, and an engine torque increase (‘throttle blip’) is used to
significantly shorten over-run downshifts.
The epicyclic geartrain utilises clutch-to-clutch synchronous shifting to ensure
that a controlled amount of torque is always being transferred during power on
upshifts. This makes the shift much smoother than in the automated manual
gearboxes adopted by some of the new XK’s competitors, where the use of an
automated clutch completely interrupts the flow of torque during shifts.
The extremely rapid shift times often quoted for automated manual transmissions
relate solely to the duration of this torque interrupt. The true shift time is
significantly longer, since the clutch must be disengaged prior to the ratio
change, and re-engaged after. In contrast, the Jaguar Sequential Shift suffers
no torque interrupt resulting in a smoother more powerful shift feel, and a very
short total shift time of approximately 600 milliseconds from the driver
touching the shift paddle to the completion of the shift event.
In fact, during development, comparison tests between Jaguar Sequential Shift
and rival automatic transmissions in the class showed the new XK’s transmission
to be the fastest system of all, changing gear at least 400 milliseconds faster
than a standard automatic and 100 milliseconds faster than the best automated
manual system.
Lightweight Vehicle Technology
Key to the all-new XK’s character is Jaguar’s industry-leading bonded and
riveted aluminum monocoque body structure, introduced with the latest XJ
saloons. The aluminum body incorporates the latest thinking in epoxy bonding and
riveting techniques to produce a chassis that is very safe, as well as very
light. In fact the new XK’s aluminum chassis is significantly lighter and
stiffer in both Coupe and Convertible form than the steel model it replaces –
over 30 percent stiffer and an impressive 50 percent stiffer respectively.
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
aluminum monocoque body structure as distinct from an aluminum spaceframe with
separate aluminum panels. Developed from aircraft industry methods, where
strength is critical for huge temperature variations and very high stresses
during take-offs and landings, 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 aluminum castings and extrusions as
well as the pressed aluminum 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 aluminum and composite materials
helps reduce transmission of noise from the engine compartment and provides a
dry area under the hood for accommodating electrical components. The new
structure also has benefits in refinement; castings are 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-aluminum shell
has durability approaching twice that of a traditional spot-welded steel body.
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