BY JOHN MELLOR | 10th Jul 2006
Such is the desensitisation of car design over the past decades we have come to expect as much reduction in noise from the tailpipe as we have come to expect diminished emissions from that same orifice.
Indeed, sometimes it has been said in jest that there should be a sound track linked into the rev counter that plays through the radio a rorty exhaust note in sync with engine speed for those lusting after the lost throaty roar of yesteryear.
But the soundtrack solution has been thwarted by Jaguar engineers who have played with multi-valve openings and closings in order to get the XK’s 4.2 litre V8 to behave suitably during various mandated drive-by noise tests and yet deliver a glorious nostalgic V8 rumble when you put the boot in.
When you are driving through the Hunter Valley with the bloke from Jaguar who was the project leader on the XK, you find out about the amount of work that goes into trying to find the balance between letting the owner hear the engine delivering all that purchased horsepower and then hushing things up for when said owner just wants to quietly cruise and contemplate the passing scenery.
Mark White, a Scot lured south at the start of his engineering career by a long-time love of Jaguars, pointed out that by manipulating the variable valves you can induce either silence or the sounds of a serious engine delivering energetically on demands from the driver.
He is right. The XK’s re-tuned carryover 4.2 V8 returns one of those key elements that combine to deliver a true motoring experience to enthusiasts. It is true of the coupe but even more the case in the convertible in which that lovely burble is heard with the roof up or down.
In this part of the market, it is these small things about car design that conspire to deliver the complete experience and so often these days we find compromise coming down on the side of mobile cacoons with a sameness of appearance that blend into the background on the road and in garages and car parks.
Here too we have another element to the conspiracy. The styling succeeds in doing for this car what a finely crafted watch does for the wrist.
You know it is special because it looks special. You know it is British because it looks British. It is the car you would expect James Bond would choose to drive when he is not at work.
But it is what is under the skin that is important for this edition of the XK because it is the move to an alloy body, using the technology pioneered within Jaguar on the XJ saloons, that delivers the greatest conspiracy of all because it makes such a huge difference to the overall result.
For those who care about these things, an alloy XK returns Jaguar to its origins in post-war England when Sir William Lyons recruited former fighter aircraft engineers into the car business because he believed the construction techniques used in making alloy aircraft was the way of the future in the car industry.
The alloy D-Type was the result of that belief. So, too, was the Jaguar 220.
Now the two core products of Jaguar, the XJ and the XK, are fulfilling Lyons’ dream – half a century later.
But apart from nostalgia, there are key benefits for XK owners.
The thing to know about the alloy technology used by Jaguar is that the various stampings that make up the entire structure of the car are not only riveted together, each facing surfaced is also bonded together with glue.
There are also fewer parts making up the body structure of this XK than its steel predecessor.
The problem with spot welded steel bodies is that the spaces between the spot welds can move marginally but in total conspire to make the body a bit like jelly (sort of) while driving. This body flex is not a good thing.
For example, the trim location points steadily wear and this creates creaks, squeaks and rattles as the car ages (if they are not already present because of the flexing in the first place). Cars with high flex inevitably suffer more quality complaints that those with stiffer bodies.
Flex is also a factor in handling. Incredibly, flex means that the wheels when in combat are not all lined up as they should be so drivers get less precise responses than they require. Think of trying the steer the jelly as opposed to steering the jelly mould.
The worst case is in convertibles where the lack of roof robs designers of strengthening support and this results in the whole fascia shaking (scuttle-shake) and the doors moving and rattling around. So reducing flex in convertibles is hard and often involves a lot more structure.
The bonding really helps when it comes to ragtops and Jaguar is claiming that it has increased the stiffness in the convertible by 48 per cent over the previous XK, with a 31 percent improvement for the coupe.
On the road this was quite apparent with the convertible exhibiting none of the kinks, rattles and scuttle shakes you expect from ragtops - although one XK coupe developed a creak in the passenger door as the day wore on.
Alloy bequeaths other benefits.
Jaguar had been beaten over the head with criticisms about the restricted interior space of the steel-bodied versions of the XK and made it part of the brief to address this problem.
So the latest XK is a bigger car. It is wider (55mm – a couple of inches) and the wheelbase - which allows for greater cabin and seating space - is increased a whopping 164mm (more than six inches in the old currency).
Headroom is increased by 20mm to 29mm (around an inch) in the coupe and convertible, shoulder room is up by 32mm and legroom is increased by 54mm (a couple of inches).
Yet this was achieved with a car that weighs significantly less that the previous model. The coupe weighs 90kg less (about the weight of a large adult).
Such is the incredible strength of the bonded alloy structure, the convertible weight has been reduced by 140kg – around the weight of two people – because steel reinforcing could be removed from the mix.
This translates into much-improved performance in spite of a car that carries its passengers in a more spacious cabin.
The new XK has the carry-over 4.2 litre V8 with four valves per cylinder although Jaguar has squeezed a little more power (219kW to 224kW) and a jot more torque (411Nm to 420Nm).
Combined with the weight savings there are clear rewards for those eager for acceleration. It clearly delivers with the engine winding willingly through the six speeds of the gearbox. From a standing start to 100km/h takes six seconds, which is not at all shabby and around the same as the Lexus SC430 although about a second slower than the Mercedes SL500.
Reduced weight also endows the now larger XK with better fuel economy, with the test cars doing around 9.5 to 10L/100km over about 700km of country driving with some city traffic thrown in. The overall economy is stated as 11.3 L/100km, which is slightly better than the stated economy of the older, heavier car.
The gearbox is easy to use in spite of six ratios to choose from.
Gone is the old J-gate that was basically a long-standing bad idea posing as a good idea. In its place is a simple fore and aft shift with just one side shift (left of Drive) that engages Drive Sport.
There are three choices.
Leave it in Drive and do nothing. Simple.
Use the paddles on the steering wheel. There is no need to select a manual mode using the paddle does that automatically. Left paddle for downshifts and right paddle for upshifts. If you forget you are in manual mode and rev out the engine because you have forgotten to upshift it will do it for you. No more red faces.
Select Drive Sport. In this mode the XK holds its gears longer and downshifts earlier (like most such systems) but a nice feature is the way it automatically changes down to supply engine braking as you apply the brakes.
While it has always been a fun part of the modern gearbox to be able to downshift using paddles on the steering wheel while powering down into corners and then up-shifting your way out again as you accelerate away, to have this occur automatically adds a new and enjoyable dimension to driving.
Standard on the XK is Jaguar’s version of the active suspension (CATS) which is designed to combine with the large tyre footprint (bigger at the back) to produce very confident and sure-footed handling.
This device is designed to monitor all the road inputs from the wheels and set the dampers in micro seconds (3000 adjustments a second, they claim) to provide the optimum balance in ride and handling.
Whatever the technology, the steering (now more definite in the straight-ahead than before) and the brakes (significantly enlarged) and the CATS combine to make the XK very reassuring when pressed into active service.
But the ride was firm and road noise was quite noticeable on sealed country roads. Grumbling from the occasional uneven surfaces was pronounced and concrete freeways surfaces dished the usual thumping on the joins you get in most cars.
Yet, on hotmix freeway and suburban surfaces, which abound where Jaguar’s are designed, this XK cat prowls as in the dead of night.
Jaguar chose to fit the optional 20-inch wheels with low-profile 30-series tyres (with a 35 aspect ratio up front) to all test cars. This meant we were unable to see if the standard 19-inch wheels delivered a quieter and smoother experience (which they should).
Visually the 20-inch wheels look sensational and, at $3000, they need to. There is a penalty to pay in terms of road noise but not enough to put you off the car.
There is a space-saver spare rather than run-flat tyre technology. This sits in a deep well in the floor of the boot which would benefit from the extra space if they were left out of the mix. Boot space is adequate. Don’t expect to get the golf clubs in without, at the very lease, unpacking the drivers.
Inside, Jaguar has provided a very appealing driving environment. The touch-screen control centre (which includes satellite-navigation, unavailable on the previous model) has a good screen size for older eyes and is nicely laid out with clear graphics and soft colouring defining and logically linking the side menus to the work areas.
The instrument panel is a combination of the traditional and the new. It features two chrome-ringed dials showing speed and engine revs looking like something very agreeable out of the 1950s design book. These flank a very appealingly-design LCD driver information display centre with just a few items to display to avoid information overload.
Jaguar has also introduced some interesting steering wheel controls that include classy knurled wheels sitting out of the spokes for adjusting things like sound volume, tuner selection and cruise control speed.
Night driving lights turn into corners and are linked to the vehicle speed to provide the most appropriate light for the driving circumstances.
The interior trim themes use walnut or poplar wood finish for the traditionalists and a charcoal and alloy finish for the modernists. In the UK the uptake on the alloy finish is running at 50 per cent.
The caramel and walnut interior on the convertible certainly looked the part with the cloth top down and will be a hit with those funding a cloth-top XK for their favourite lady.
But the caramel top of the fascia reflected significantly in the windscreen with the sun on it. Maybe they won’t care.
There are convenience features like front/rear park assist, rain-sensing wipers, key-less entry, Bluetooth compatibility, MP3 reader, and 10-way power seat adjust with memory.
Standouts on the safety front include an active roll bar for the convertible (with appears through the back window glass on sensing roll over) and automatic deployment of the bonnet for pedestrian protection when it senses you are about collect the neighbourhood drunk across the front of the car.
The XK cat is, to coin a phrase, a great leap forward.