ENGINEERING

Underlying the new visual design language, the XF is the product of a new generation of design technology, materials and manufacturing opportunities, as Phil Hodgkinson, Jaguar Programmes Director, explains:

“The engineering disciplines behind the XF are as ground-breaking as its new design language. New development processes and computer tools allowed us to work through the programme at a quicker pace than anything previously; new technologies and materials combine strength with lightness; and Jaguar craftsmanship, too, has explored new, exciting contemporary avenues.”

Virtual Process (VP) and Virtual Series (VS) are the cutting-edge technologies used by Jaguar to take the XF from concept to reality. These techniques use massive computing power and sophisticated modelling programmes to create components and even whole vehicles in the virtual world, before building physical parts and perfecting the systems and processes to manufacture the car. The XF represents the first time that VP and VS tools have been used by Jaguar throughout a complete vehicle programme - from vehicle development, to production feasibility studies, to build planning.

But VP also dramatically improves overall quality, by allowing rapid sign-off of component designs, and eliminating the early physical prototype stage. With VP, when prototypes finally are built, they are intended only to validate what is already known, not to develop areas that are still unresolved. Fully representative vehicles are used for physical evaluation, including on-road testing, crash-testing, hot and cold climate testing, and durability testing. At the same time, the VS programme is working on everything that is needed eventually to build the car – leading to significant improvements in craftsmanship, efficiency, even long-term serviceability.

New technology is also key to the XF’s construction. It was the first programme within Jaguar to use the next-generation CAD programme C3PMG, which combines an all-new CAD-modelling software package with an all-new data-management package – opening the way to exceptional strength without unwanted weight. The design is led by safety needs, especially by the latest side intrusion and SUV over-ride requirements. The reinforced passenger safety cell incorporates new thinking from the lower side rails up.

The XF adopts the latest generation steels, especially in the upper body – including high carbon steels, dual-phase, hot-formed boron steels, and bake-hardened steels to form a vertical safety ‘ring’ around the occupant cell. As well as combining strength with lightness, these steels improve corrosion resistance, by making best use of zinc and improving e-coat paint flow – and new thinking means that in spite of their strength, the XF’s A and B-pillars are impressively slim, to the benefit of both visibility and accessibility. Similarly, the lower sills are the first component on any Jaguar to use incredibly strong, dual-phase DP600 steel.

Second-generation Pedestrian Contact Sensing System – the acclaimed safety system introduced by Jaguar on the XK – is included on the XF (market dependent). This can mitigate pedestrian injury by firing actuators that deploy the bonnet, resulting in a cushioned space between the bonnet and engine hardpoints. The system builds on the technology proven in the XK, using higher resolution sensing and an active rear-hinged bonnet.

Every XF also comes with two-stage driver and front passenger airbags, side and curtain airbags and Seat Occupant Sensing systems to help ensure the airbags work precisely and only as needed in every circumstance. Front-seat occupants also have the added protection of an Anti-Whiplash System and ‘soft-landing’ technology in the seat-belt retractors to soften contact with the front airbags.

Other changes - many of them made possible by extensive use of the Virtual Process during the development programme - improve craftsmanship by optimising the manufacturing process. Close attention to optical quality creates the smallest, most consistent panel gaps and other new measures improve resistance to minor impacts, making accident repairs easier and less expensive, so contributing to significant cost-of-ownership benefits.

SUSPENSION

The XF’s class-leading torsional rigidity has significant benefits for refinement and provides the perfect platform for a suspension system that is a further development of the XK sports car, and delivers a ride/handling balance and steering characteristics absolutely in line with the XF’s sporting looks. Unequal length wishbone front suspension with weight-saving aluminium components, and multi-link rear suspension are both subframe mounted for maximum control, including excellent straight-line stability and strong anti-dive characteristics under heavy braking, with minimum road noise and vibration.

The only suspension variations on the XF are between the V6 petrol, V6 diesel and V8 naturally aspirated models, which all use finely tuned passive suspension, and the SV8, which for all markets uses Jaguar’s Computer Adaptive Technology Suspension (CATSTM). The latest CATSTM is a sophisticated system shared with the new Jaguar XK sports grand tourer. It uses electronically controlled, two-stage, adaptive dampers whose characteristics are automatically adjusted within milliseconds in response to road conditions and driving inputs, for the optimum balance between comfort and control.

BRAKES

The XF uses large 326mm x 20mm vented front discs on all naturally aspirated models and 355m x 32mm vented front discs on the SV8 model for powerful, balanced braking performance. The rear discs on all versions measure 326mm x 20mm.

An extremely stiff pedal box contributes to a particularly solid pedal feel, and the brake assistance is tuned to give a very progressive feel, while softening the initial response.

The XF uses Jaguar’s Electric Parking Brake, with a small and neat, chromed release in the centre console. As the XF’s braking system communicates electronically with the shift-by-wire technology of the JaguarDrive SelectorTM function, so the Parking Brake is released automatically as Drive is selected – although the Parking Brake can also be engaged and disengaged manually if appropriate, through the release.

STEERING

Variable ratio power-assisted steering is standard on every version of XF, for reduced parking effort at low speeds and greater precision and feedback at higher speeds - and especially for positive weight to the on-centre feel, which is part of the new dynamic flavour. Steering effort at manoeuvring speeds is also reduced on diesel models.

The new XF adopts an electronic steering column lock - for compatibility with passive entry mode and the Jaguar Smart Key SystemTM. There is no longer a key barrel on the column. however the electronic lock satisfies Thatcham security legislation for the UK market.

The XF’s steering wheel includes cruise-control, JaguarVoiceTM (where fitted) and audio controls - including volume, and radio channel pre-sets. The source button toggles through AM/FM/CD, plus any external device functions. The select buttons allow features such as CD track change, radio channel pre-set selection or iPod? or MP3 track change if such a device is in use.

WHEELS AND TYRES

Depending on market and model, the XF is available with 17, 18, 19 or 20-inch wheels; the SV8 being the only car in its class to have 20-inch wheels as standard. All are cast in aluminium alloy and every design combines maximum strength with minimum weight. All cars for the majority of markets carry the same specification of 18-inch diameter alloy mini-spare. To satisfy Thatcham security stipulations, there are also 20 variations of anti-theft locking nut.

For major European markets, cars with 17 and 18-inch wheels are fitted with the Jaguar Tyre Repair System as a space and weight-saving alternative to the mini-spare. The compact Jaguar Tyre Repair System replaces the spare wheel, jack and tool kit, and can effect a temporary repair of any puncture of up to 6mm diameter in the tread area - sealing the hole and re-inflating the tyre to enable the car to be driven to where a permanent repair or replacement can be carried out. When fitted the Jaguar Tyre Repair System liberates an additional 40 litres of stowage space under the boot floor.

DRIVER AIDS

The XF’s main control module governs many key safety functions including Emergency Brake assist (EBA), Electronic Brakeforce Distribution (EBD), Anti-lock Braking System (ABS), Traction Control through engine and brake intervention, Dynamic Stability Control (DSC), Cornering Brake Control (CBC) and Engine Drag Torque Control (EDR). And for the first time, the XF adds Understeer Control Logic, which has been designed to mitigate understeer by intervening through the engine management and braking systems to decelerate the car and help restore grip to the front wheels.

A two-stage DSC system similar to that featured on the new XK is standard equipment. It combines the normal on-off switchable DSC function, which reacts as soon as it detects slip, with Trac DSC, which allows more slip before intervening – better for a more sporting driving experience. It also allows a degree of wheel overspin on deep soft surfaces, which is essential for running with snow chains. The system defaults to normal ‘DSC on’ with each ignition-on sequence.

In Dynamic Mode (SV8 only), pressing and holding the DSC button fully disables the system, allowing an experienced driver to exploit fully the capability of the chassis, where conditions allow. Mode selection is confirmed on the instrument cluster display.

Also new on XFs fitted with Adaptive Cruise Control (ACC) is Electronic Brake Prefill. This senses any rapid throttle lift-off and initiates a small brake hydraulic pressure build-up in anticipation of the brakes being applied, to give better pedal response and slightly shorter stopping distances.

JaguarDrive ControlTM offers different modes that interact with the DSC system, engine and gearbox, to change the characteristics of engine mapping, transmission shifts and brake interventions depending on driving conditions and circumstances. On naturally aspirated cars JaguarDrive ControlTM has Normal and Winter modes, on the SV8 model there are Normal, Winter and Dynamic modes - the last of these to allow a more purposeful driving style.

POWERTRAIN

The new XF will be available with a choice of four engines - 2.7-litre V6 turbodiesel, 3.0-litre V6 petrol, 4.2-litre naturally aspirated V8 petrol, and 4.2-litre supercharged V8 petrol (depending on market). All will have that classic blend of power and refinement that makes Jaguar stand out from its rivals, says Mick Mohan, XF Chief Programme Engineer:

“The XF’s engines combine effortless performance, unrivalled character and an impeccable pedigree. The six-speed automatic transmission is the best Jaguar has ever had. The Jaguar Sequential ShiftTM manual gearchange adds a whole new level of functionality. This combination – already proven in the XK– produces excellent powertrains for a very sporting Jaguar.”

Both petrol and diesel V6 engines are offered in Luxury and Premium Luxury models; the naturally aspirated V8 will be Premium Luxury only (and Luxury for US models) and the supercharged SV8 has its own unique specification, for a very logical, easily understood range with only six major variants.

The Euro IV compliant twin-turbocharged 2.7-litre 24-valve V6 diesel delivers high efficiency, high performance and class-leading refinement – its headline figures including 207PS (EEC) and 435Nm (EEC) of torque. With its Compacted Graphite Iron (CGI) cylinder block and aluminium cylinder heads it is the lightest diesel engine of its type and size - making a significant contribution to the new XF’s power-to-weight ratio, performance and fuel economy.

The V6 diesel features the latest generation high-pressure Common Rail direct-injection, ‘multiple pilot’ injection, and piezo-electric injection control, allowing sophisticated management of the injection patterns to make combustion smoother and quieter. Four valves per cylinder and advanced combustion chamber shapes contribute to high combustion efficiency with low combustion noise, alongside very low mechanical noise levels.

Emissions are further reduced by using twin variable-geometry turbochargers with electronic control, exhaust gas recirculation, and a variable-swirl intake system. Using two small turbochargers, with ‘drive-by-wire’ throttle control, rather than one larger unit, also gives a quicker, smoother response.

The 3.0 litre V6 petrol engine is another compact, lightweight, all-aluminium design with four overhead camshafts, four valves per cylinder, VCP Continuously Variable Cam Phasing and variable geometry air intakes. It produces 240bhp (SAE)/238PS (EEC) and 221lb ft (SAE)/293Nm (EEC) peak torque - with more than 80 percent of peak torque from below 1500rpm to maximum engine speed at 6800rpm.

Variable Camshaft Phasing produces faster response and performance at all engine speeds - with more torque at low speeds and maximum power at high speeds. It also provides internal exhaust gas recirculation, reducing both hydrocarbon and NOx emissions.

The 4.2 litre V8 comes in naturally aspirated or supercharged versions. With a ribbed aluminium block and cylinder heads it is very light but extremely strong, and its superb structural stiffness minimises radiated engine noise and increases mechanical reliability. The V8’s exhaust system has also been completely retuned to remain quiet at cruising speeds but deliver a substantially more purposeful V8 roar under hard acceleration.

In naturally aspirated form it develops 300bhp (SAE)/298PS (EEC), and 310lb ft (SAE)/411Nm (EEC) of torque. The supercharged version uses a highly efficient rotor-type supercharger, belt-driven from the crankshaft. It develops 420bhp (SAE)/416PS (EEC), and 408lb ft (SAE)/560Nm (EEC) of torque from low engine speeds. Just as important as the supercharged engine’s peak torque is the way the usable torque is spread across a wide rev range - with at least 86 percent of the peak from 2000rpm to maximum engine speed.

A superior six-speed automatic transmission – renowned as one of the best in the world and already proven in other Jaguars - is used on all versions of the new XF – there is no manual gearbox option. The transmission is a key element in the XF's sporting character, its adaptive gear-changing strategies responding both to road conditions and the way the car is being driven, giving the smoothest shifts and optimum performance. Adding another layer of driver focus, the transmission is controlled by the new JaguarDrive SelectorTM with the option of manual selection through Jaguar Sequential ShiftTM. The JaguarDrive SelectorTM is also used to access the XF’s Sport mode which uses shift-by-wire technology pioneered on the XK.

These high-tech, modern powertrains give every XF model outstanding performance. The 2.7-litre V6 diesel reaches 60mph in just 7.9 seconds (0-100kph in 8.4 seconds) and has a top speed of 143mph (229kph). The 3.0-litre V6 petrol version sprints to 60mph in 7.9 seconds (0-100kph in 8.3 seconds) and goes on to reach 148mph (237kph). The naturally-aspirated V8 model has a superb 0-60mph time of just 6.3 seconds (0-100kph in 6.6 seconds) and has an electronically limited top speed of 155mph (250kph). Lastly, the supercharged SV8 XF storms to 60mph in just 5.2 seconds (0-100kph in 5.5 seconds) and, like the naturally aspirated V8 is limited to a maximum of 155mph (250kph).

DRIVING DYNAMICS

Delivering the highest levels of driver enjoyment is a must for any Jaguar, so it is essential that the XF’s driving dynamics live up to its powerfully athletic looks. Underpinned by the stiff platform, wide track and finely resolved suspension, steering and brakes, the XF’s dynamic flavour combines the comfort and refinement of a luxury saloon with the grip, balance, responses and stability of a sports car. The result is a dynamic character that delivers real driver involvement, as far removed from the premium saloon crowd as are the XF’s bold looks.

Chief Engineer, Vehicle Integrity Mike Cross explains the development processes behind the new car:

“Two key objectives defined the XF’s dynamic flavour – firstly that its driving abilities should match its sporting coupe-like looks, and secondly that it should have Jaguar’s unique balance of ride, handling and refinement. The XF succeeds on all counts and the result is a very special experience.”

Every XF model uses Jaguar Sequential ShiftTM transmission control, allowing manual gear selections in the automatic transmission via ‘paddle’ switches mounted on the rear of the steering wheel, in either Drive or Sport mode.

But sporty is only half the XF driving dynamics story – refinement is equally important, and equally impressive. With its stiff shell, smooth powertrains and extraordinary attention to acoustic management (including a secondary bulkhead and dual-isolated subframe on all versions), the XF has outstanding NVH performance to match the best in class. At 30mph (50kph), for instance, the interior noise level is only 65.6dB, below its nearest BMW 5 Series rival, even when the XF is on larger wheels. Special attention has been paid to the V6 diesel model, whose sound quality is so impressive it is hard to tell what engine lies beneath the bonnet. The V8 XF takes lessons from the XK with an exhaust system tuned for an overtly sporty sound quality, especially when accelerating hard – again, just as the looks promise.