When Jaguar revealed the F-Type as its new sports flagship most pundits - including at least one at Jaguar Land Rover - predicted that the bigger, heavier XK coupe would gain a little weight and a lot of luxury, in the process of morphing into a true GT car.
That could still happen but, in the meantime, the performance junkies at Jaguar's ETO skunk works have produced the exact opposite - a marginally street legal track-day special that global brand director Adrian Hallmark describes as “the most extreme XK yet”.
And only 30 of them will be built, all destined for North America, which is why the car is making its world debut today (27 March) at the New York auto show.
It's motivated by Jaguar's proven five-litre supercharged V8, tuned in this application to deliver 405kW at 6500rpm and 680Nm from 2500-5500rpm, driving the rear wheels via a six-speed paddle-shift transmission and an active electronic differential. 0-100 is quoted at 3.9seconds, top speed is electronically limited to 300km/h.
Then it gets really interesting.
The front and rear suspension arms, uprights, wheel bearings, bushings and rear subframe are all new, derived from those developed for the F-Type, and specifically set up to increase lateral suspension stiffness for more precise and responsive handling.
Motorsport-derived dual springs are mated to an adaptive damping system, and the dampers are also adjustable for ride height. Front and rear spring rates are 68 percent and 25 percent stiffer respectively than on the XKR-S, and the damper set-up is much more track-focused, providing increased levels of body control and grip.
The adaptive damping has been specifically tuned for the XKR-S GT so that the suspension parameters change to deliver a higher level of body control with maximum traction and grip.
The XKR-S GT's front track is 52mm wider than that of the XKR-S while the rear remains the same. The steering rack has been lifted from the F-Type, with a correspondingly faster ratio and retuned steering valve for lightning-fast turn-in and response to steering inputs.
The XKR-S GT is also the first production Jaguar with carbon-ceramic brakes.
Internally ventilated and cross-drilled 398mm front and 380mm rear discs combine with six-piston yellow monobloc calipers at the front and four-piston units at the rear - each branded with 'Jaguar Carbon Ceramic' script - to deliver race-car levels of fade-free stopping power and brake pedal feel, thanks to an electronic pre-fill system.
The system pressurises the brakes every time the driver comes off the throttle, for a very short and consistent brake-pedal travel, giving ferocious initial bite and increased levels of confidence.
The ceramic brakes also reduce unsprung weight by a healthy 21kg, and Jaguar claims that they have a significantly longer lifespan than a standard system.
The XKR-S GT runs on special gloss black forged, lightweight alloy rims shod with 255/35 front and 305/50 rear Pirelli Corsa tyres.
AERO KIT
The XKR-S GT has a carbon-fibre racing-style wrap-around front splitter that extends 60mm forward to start the management of airflow around, over and under the car. Carbon-fibre twin dive-planes and wheel-arch extensions smooth airflow around the car, and an aluminium front panel guides airflow under the car as well as enhancing engine and brake cooling performance.
A carbon-fibre rear diffuser ensures the smooth exit of air from under the car, while the carbon-fibre rear wing works in tandem with the bootlid spoiler to produce 145kg of downforce when the XKR-S GT is running flat out.
Bonnet louvres help cool the engine cooling, reduce underbonnet air pressure and improve airflow through the front end of the car.
The XKR-S GT is only available in white, with special graphics and Jaguar R-S GT script on its louvred bonnet. The dark grey interior with red accents features 16-way electrically adjustable 'Performance' seats finished in soft grey leather and suedecloth with the Jaguar and R-S GT scripts on the backrests.
The headlining and steering wheel are finished in black suedecloth headlining, with aluminium paddle shifters as standard, and special logos on the treadplates and console.
Trust Jaguar director of design Ian Callum to have the last word.
“The XKR-S GT has been designed purely by the laws of physics,” he said.
“It was developed in the wind tunnel and on the racetrack to create as much high-speed stability and downforce as possible. Nothing has been styled for the sake of it. It was an exercise in efficiency and the result is a car that's raw, focused and devastatingly quick.”