Big cat getting ready to roar

Under the ZKR bonnet is a power-pack of hefty dimensions.

Big cat getting ready to roar

Other than the mesh grille and those evocative bonnet vents, visual hints at the monster within are few. But lift the bonnet and it's another story.

For this Jaguar is fitted with a supercharged V8, a development of that used by the Range Rover Sport, its 313kW and stonking 560Nm of torque a substantial lift over the standard XK V8's 224kW and 411Nm.

Jaguar says the main ingredients are the Eaton supercharger, a lightweight water-cooled 90-degree V configuration, and continuously variable valve timing to spread the torque delivery across the rev range. Twin air inlets improve breathing and a variable inlet camshaft timing enhances the torque on offer, particularly at low revs.

The ripsnorting powerplant is mated to the same six-speed sequential shift auto as the XK, but reprogrammed for quicker shifts. The result is a zero to 100 time of about five seconds - a little slower if you choose the convertible.

Jaguar's designers were worried the supercharger whine would be annoying, so they tuned the exhaust to compensate - calling it an active exhaust system - resulting in a refined soundtrack while cruising but a hairy-chested V8 roar when accelerating hard.

The springs and dampers front and rear were uprated and the spring rates increased.

The computer suspension's adaptive damping, stability and traction control have all been tweaked to suit and even the steering has been tuned for more weight and better response.

The standard wheels are 19-inch. But 20-inch hoops will be available and they are design chief Ian Callum's preference - he has a long history of admiring cars, admitting to smearing showroom windows when a boy.

The brake discs are larger - which is good, given the car is 70kg heavier than its less powerful sibling. That's not attributable to body reinforcements - the all-alloy, riveted and glued monocoque proved strong enough already, although a rear suspension brace has been added.

This new XKR is a good 70kg lighter than its predecessor - 100kg lighter when convertibles are compared.

So it's not surprising that it's faster, with the power-to-weight ratio improved by 12 per cent and the torque-to-weight ratio up by 7 per cent.

Yet even Jaguar head office doesn't bill this car a worldbeater.

"Our aim was to ensure that the car's characteristics remained in balance despite the significant increase in power over the XK," said chief engineer Mike Cross.

"With that as our base, our brief was to create 'XK plus 30 per cent' - the ultimate sports GT for the real world.

"We wanted the performance and dynamism you would expect of an XKR, but were careful to retain that exceptional blend of sporting luxury every Jaguar must have."

So Jaguar New Zealand won't be selling this car as the ultimate performance machine. The premium performance market is already hotly contested.

Instead, the XKR will be billed as the ultimate upgrade - a premium XK with more mumbo. But if the hotly rumoured XKR-R is built the picture could change.

By increasing the 4.2-litre engine's size or upping supercharger boost pressure more power could be found - giving Jaguar the opportunity for a limited-edition car that could put the frighteners on the likes of BMW's M6.