The Jaguar XKR | Part Three

Jaguar XKR

Jaguar XKR

Transmission

Jaguar's Sequential Shift uniquely combines all the speed and involvement of a sequential manual gearbox with the comfort and convenience of a full automatic. The system consists of steering wheel-mounted paddles and a conventional gear selector lever, allowing the driver to switch between three automatic or paddle-operated gearbox modes.

Whereas an automated manual gearbox interrupts the flow of torque during the gearchange – while the clutch is disengaged - the Jaguar's gearbox maintains the flow of torque throughout the shifting process. This results in gearchanges that are not only quick, but also remarkably smooth. Gearshifts are achieved in less than 600 milliseconds, from the point at which the driver operates the shift paddle to the point at which the shift is complete.

In fact, during development, comparison tests between Jaguar Sequential Shift and rival automatic transmissions in the class showed the 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.

The three gearbox modes give the driver total flexibility to use the transmission to match whatever driving style he or she chooses. In Drive mode, the gearbox behaves as a conventional automatic, with the software optimised for every day driving conditions providing all the benefits of a best-in-class automatic transmission.

In Sport mode, the gearbox's adaptive software becomes more prevalent, adapting and reacting more dynamically to demanding conditions. This software takes account of the prevailing conditions and driver's inputs and adapts accordingly. For example, it recognises when the car is negotiating a curve, and holds the gear accordingly; Hill Recognition enables the XKR to choose the ratios to optimise the ascent or descent of a hill; the gearbox’s software will also match the engine speed precisely to the engine and road speeds, ‘blipping’ the throttle during rapid downshifts.

Manual mode is activated by simply operating one of the steering wheel-mounted paddles, and delivers a state-of-the-art manual gear shift feel from the automatic transmission.

Chassis, Suspension And Brakes

To ensure optimum ride and handling the XKR’s springs and dampers are uprated compared to the normally aspirated XK. The front spring rate is increased by 38% and the rear spring rate by 24%. Allied to the Servotronic steering system, which has also been tuned both mechanically and electronically to give the steering more weight and even greater response, the uprated suspension ensures confidence-inspiring handling without any loss in refinement and comfort levels.

Because of the inherent strength and stiffness of the chassis, the only significant addition to the XKR’s structure is an additional rear suspension brace mounted between the rear damper towers to accommodate the significant increase in rear spring rate. This also allows the Convertible to utilise the same dynamic settings as the Coupe model.

The Computer Active Technology Suspension (a two-stage adaptive damping system that ensures the optimum balance between ride and handling) and new switchable Dynamic Stability Control with Traction Control System (Trac DSC) have also been recalibrated to cope with the additional power of the supercharged engine.

As significant to the XKR as the increases in power and torque are the major improvements in strength and weight thanks to its advanced all-aluminium architecture. Unique in the industry as a complete aluminium monocoque body structure, as distinct from an aluminium spaceframe with separate aluminium exterior panels, its properties come from both the way the bodyshell is designed and constructed and the use of new joining technologies.

continues... | Part Four
Published 2 July 2006 Melanie Carter

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