Jaguar XKR refined but still wild

“The full initial allocation of XKRs for our first six months has already been sold . . . interest in the car has been unbelievable,” says Land Rover spokeswoman Lesa Horntvedt. “The wait for it is out to six months.”

That initial allocation was 60 cars — not a lot in global terms — but it's been some time since anyone lined up for a Jag. Jaguar Australia sold 1011 cars last year, of which 88 were the XK8, the new model of which was launched mid-year. Those figures are already looking pale next to a 2007 first quarter that has seen 30 XK8s delivered and 60 XKRs (at $227,900 for the coupe and $249,900 the convertible) presold.

The XKR takes the core of the basic XK, adds a load of performance and a minimum of styling changes.

“When we started down this track there were some truths we knew we had to face,” says Jaguar senior body engineer Mark White. “The goal was to create the ultimate sports GT and to do it we set the target of exceeding the XK by some 30 per cent in a range of performance criteria.”

What the engineers aimed for was a benchmark of five seconds for the 0-100km/h sprint. They achieved a 5.0 flat for the coupe and 5.2 for the convertible but, more important, performance had to be accessible in the crucial mid-range for overtaking and it had to be refined.

A large part of the XKR's credentials come from the high standards set for the new XK. Although there was no need to stiffen the superbly rigid chassis and all-aluminium body of the XK, the XKR engineers concentrated on providing an engine with extra heart, suspension that delivers a stiffer ride without additional harshness, and brakes capable of reining in a rampant XKR.

Strapping the twin induction supercharger to the 4.2-litre V8 was the obvious first step and with it came variable valve timing on both inlet and outlet cams. The power boost was some 40 per cent over the XK, taking maximum power to 306kW at 6250rpm and a thumping 560Nm of torque from 4000rpm.

The whipcrack engine has been coupled to the latest of the ZF auto gearboxes, as seen in the Maserati Quattroporte and Ford Falcon. Featuring shift changes as smart as 600 milliseconds and as smooth as custard, the box can be driven as a full automatic in cruise mode, a sports automatic with computer-generated blips on the downshifts or as a full-control manual utilising the wheel-mounted paddle shifts.

To keep the extra urge from its attempts to separate car and road, the spring rates were stiffened 38 per cent at the front and 28 per cent at the rear, rollbar thickness was increased a millimetre and damper response improved by 25 per cent.

The CATS (computer active technology suspension), which switches the dampers between soft and firm, has a similar response time to the XK's but has been tweaked to switch from soft to firm earlier.

The other critical area of improvement is in braking. Compared with the XK, the R car has 26 per cent greater swept area on the discs and a huge 37 per cent improvement in cooling efficiency.

One of the joys of the XKR, particularly the convertible, is the oh-so-angry exhaust howl. Its throaty note is a simple affair: the more you poke it, the louder it growls.

However, poke it really hard and you risk scaring yourself.

What's not immediately obvious is the expected induction whine of the supercharger. It's far more muted than the outgoing model — or than the same engine tuned for the S-Type R.

Absolutely reassuring about the XKR at full charge is the rock-like stability. It does not so much attack the road as seduce it, caressing the corners with gentle assurance. With the stability control in operation the intervention is gentle and unobtrusive.

Each time you think the limits of adhesion are approaching and push that little harder, the chassis finds even more limpet-like grip.