3/1/13

Overview: Jaguar XFR-S

Jaguar’s XFR-S saloon made its global début at the Los Angeles Auto Show in the autumn. The Company describes the XFR-S as the fastest, most powerful and agile sports saloon it has ever built.

Developed by Jaguar Land Rover’s specialist ETO division, the XFR-S features bespoke powertrain, chassis and body enhancements. With 550PS and 680Nm from its uprated five-litre supercharged V8 engine driving through an eight-speed ZF transmission, the XFR-S is capable of reaching 60mph in 4.4-seconds before going on to an electronically limited top speed of 186mph. These outputs represent gains of 40PS and 55Nm over the XF-R; the increases have been achieved through revisions to the engine management system and improvements to intake and exhaust gas-flow. The all-aluminium quad-cam V8 features spray-guided direct injection (SGDI) and dual independent variable cam timing (DIVCT).

Jaguar XFR-S.

The high-pressure die-cast lightweight aluminium block is stiffened with cast iron liners and cross-bolted main bearing caps. The four-valve cylinder heads are constructed from recycled aluminium, between them sitting the Roots-type twin vortex supercharger fed by two intercoolers which feature their own water-cooling circuit. Larger front air intakes in the lower bumper of the XFR-S allow greater volumes of air to be fed into the engine. The intake system also features a ‘symposer’ that channels more of the induction noise into the cabin.

A number of driveline components have been uprated. These include the driveshafts, the central bearing on the propshaft and the torque convertor.

The eight-speed ZF gearbox uses Quickshift, a system developed for the F-Type. When downshifting — either manually or in Sport mode — the engine management system automatically blips the throttle. This function also allows the transmission to perform multiple and very rapid downshifts during hard braking.

When operating in automatic mode, the transmission can detect the manner in which the car is being driven by monitoring acceleration and braking, cornering forces, throttle and brake pedal activity, road load and kickdown request. On detecting a more enthusiastic driving style, the transmission will automatically make the gearshifts more aggressive and move the shift-up point higher in the rev range.

Corner Recognition senses when the car is negotiating a bend, the transmission holding the correct gear for the exit. The transmission will also recognise when the car is performing a series of overtaking manoeuvres requiring rapid changes in throttle position and, rather than change up, remain in a lower gear ready for the next demand for acceleration.

The 8HP transmission also allows the XFR-S to be offered as standard with Jaguar’s stop-start system. This automatically shuts down the engine when the car comes to a halt and the brake pedal is depressed. When the brake is released, the system will restart the engine in less time than it takes for the driver’s foot to move to the accelerator. (So if the driver applies the parking brake and releases the foot pedal, the engine restarts.)

A twin solenoid system, it allows for ‘change of mind’ functionality, bringing the engine back up to speed even during its run-down phase if, for instance, the car is coming to a halt at a junction and the driver sees an opportunity to join the traffic flow.

Front and rear suspension upgrades are aimed at improving response, with lateral stiffness up by 30 per cent. The electronic active differential and Dynamic Stability Control systems have also been recalibrated. Aerodynamic changes, with extensive use of carbon fibre construction, reduce lift by 68 per cent.

Front suspension knuckles have been revised in line with those found on the XKR-S to achieve the increased camber and castor which, along with new wheel bearings, improve steering and handling precision. The steering system has additionally benefited from the fitment of the valving developed for the F-Type.

At the rear, a new subframe has enabled revisions to suspension geometry which, allied to stiffer bushes — new rear knuckles and working in tandem with the stiffer springs — increase stability and response.

The tyres, developed in conjunction with Pirelli exclusively for the XFR-S, are 10mm wider all round: 265/35 and 295/30. The wheels are half an inch wider at the front and an inch wider at the rear in comparison to the wheels found on the XFR, but their construction means there is no weight penalty to be paid. The difference between the wheel rim and tyre width increases has the effect of pre-loading the sidewall to improve handling and steering response without adversely affecting refinement.

Jaguar’s Adaptive Dynamics system actively controls vertical body movement, roll and pitch rates through the use of continuously variable dampers. The system monitors driver inputs and the road conditions, adjusting damper rates in response up to 500 times a second to optimise stability and agility. The driver’s selection of Dynamic Mode offers enhanced body control by moving the damping rates to the firmer end of the available range.

The Jaguar active electronic differential — which can apply full locking torque almost instantaneously when necessary — has been recalibrated in order to exploit the greater grip offered by the wider rear tyres, the more precisely controlled suspension and the engine output. Working in parallel with the differential, the ‘Trac DSC’ setting of the Dynamic Stability Control system now offers the enthusiastic driver more opportunity to explore the outer edges of the handling envelope while nevertheless providing a discreet safety net.

Jaguar’s High Performance Braking System features 380mm front and 376mm rear discs, internally ventilated; on the XFR-S the brakes benefit from additional cooling provided by under-body air channelling.

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