| The introduction of the 2.7 litre twin-turbodiesel to the XJ range marks a significant development for Jaguar’s flagship model. Following on from the highly successful introduction of diesel engines to the X-Type and S-Type model ranges, the new XJ 2.7 twin-turbodiesel means Jaguar now offers a diesel alternative across its entire saloon range, ensuring that the marque can meet the increasing demand for diesel-engined cars in the European marketplace.
The XJ already ranks as the most technologically accomplished Jaguar has ever built. It is the first production Jaguar to be constructed with a lightweight aluminium monocoque structure; a unique feature that gives the XJ significant competitive advantages over its rivals. A lighter car means faster acceleration and shorter stopping distances, as well as frugal fuel economy and range, particularly when combined with the latest fuel-efficient diesel engine. The aluminium monocoque design of the XJ offers improved stiffness and safety performance over the conventional steel body of the previous model, meaning the customer not only benefits from the weight saving associated with aluminium, but gets the added benefit of exceptional ride and handling as well as being extremely quiet and safe.
Launched in Jaguar’s mid-range S-Type saloon in 2004, Jaguar’s twin-turbo V6 diesel sets new standards in refinement and performance. Producing 207 ps (152 kW) EEC a diesel-powered XJ saloon will accelerate to 60 mph in just 7.8 seconds, while a powerful wave of torque (435 Nm) is available virtually throughout the powerband to ensure instantaneous acceleration in every gear.
Yet the efficient diesel engine and light overall weight of the car means low running costs thanks to an average fuel consumption figure of 8.1 l/100 km (35 mpg) and low CO 2 emissions.
The highly efficient 24-valve engine features advanced technologies, including the latest generation high-pressure, common-rail, direct-injection fuel system and a lightweight, compacted graphite iron (CGI) cylinder block.
The outstanding strength and durability of CGI means that less material is needed than for a conventional cast-iron block, ensuring reduced engine weight and length. In fact, the new diesel engine is the lightest unit of its type, at just 202 kg. This significantly contributes to the excellent power-to-weight ratio and fuel economy.
Other features at the heart of the engine provide the capability to deliver high performance and excellent durability. Cast aluminium pistons incorporate ‘double wave-gallery’ cooling. In this process, oil is sprayed precisely onto the inside of the pistons from jets in the block. The oil then flows through two internal wave-shaped channels to help cool each piston crown. This arrangement also has the indirect benefit of reducing piston ‘slap’ noise.
Management of the engine’s noise characteristics has focused particularly on injector tick and combustion noise, which is controlled through the use of next-generation common-rail technology, including ‘multiple-point’ injection and closed-loop injection control, which ensure that the combustion is smooth under all operating conditions.
The fuel quantity provided by each injector is controlled by a piezo actuator, which enables highly accurate fuel metering of up to five injections per cycle. These features provide an extremely fine spray of diesel fuel, which ensures the most uniform fuel-air mixture possible, resulting in a more complete combustion process. As a result, the diesel engine is able to achieve both high power and the desired emissions capability.
From the outset, the 2.7 twin-turbodiesel engine was designed to meet future emissions levels. However, further advances in reducing emissions since the launch of the S-Type twin-turbodiesel have been made through changes to the fuel injection system, utilising higher injection pressures and different injector spray patterns. The calibration of the electronically actuated turbochargers, the exhaust gas recirculation system and port deactivation have also been revised. With the addition of a catalysed diesel particulate filter (CDPF), the advanced design of the V6 engine ensures it exceeds Euro 4 emissions requirements.
Aiding both performance and emissions is a forced induction system, comprising twin-turbochargers with state-of-the-art electronic actuation. Traditionally, turbochargers are vacuum actuated, but this new form of rotary electric actuator gives a higher degree of control, providing benefits in the areas of emissions and transient engine performance, as well as in balancing performance and emissions between the two cylinder banks. The turbochargers are a low inertia type for quick, responsive, power delivery.
The high-grade aluminium alloy cylinder heads are equipped with four valves per cylinder and double overhead camshafts. This combination provides optimum induction and exhaust actuation, with attendant benefits in performance and emissions. The cylinder head design includes a port deactivation system and pistons with toroidal combustion chambers, producing a highly efficient combustion capability. A low - by diesel standards - compression ratio of 17.3:1 contributes to improved emissions quality, quieter combustion and compatibility with the engine’s unique forced induction system. In a diesel engine, reduced compression means less heat build-up in the piston bowl and more efficient fuel burn, resulting in lower levels of pollutants.
Electronically controlled, self-levelling air suspension is standard on all models which automatically lowers the car at speed to provide high-speed stability and improve aerodynamic efficiency. Jaguar’s Computer Active Technology Suspension (CATS) uses computer technology and sensor feedback to automatically adjust damper settings. The result is a unique combination of agile handling, outstanding ride comfort and excellent driver control.
Noise intrusion into the cabin is reduced to a remarkably low level with the Integrated Acoustic Damping System. This uses high acoustic absorption on the underside of the bonnet, airtight seals between the bonnet and engine compartment and a new double-skin bulkhead structure to dramatically reduce engine noise inside the cabin.
For the first time on all XJ models, acoustic laminated glass further minimises the intrusion of external noise into the cabin. Wind noise and engine noise levels are consequently reduced by up to 5 decibels above standard laminated glass. A revised secondary bulkhead structure has also been introduced to the engine compartment of all XJ models – both diesel and petrol – to reduce interior noise levels by up to 5 decibels.
The XJ Diesel is also the quietest vehicle in its class for exterior noise, with the noise level measured by the Vehicle Cerification Agency being 7 decibels (A) lower than the EU legal limit for diesel vehicles. In order to achieve this, the exterior noise package has been significantly enhanced.
The 2.7 TDVi XJ also sets an industry first, being the first car in its class to feature electronically controlled active engine mounts, designed and developed in conjunction with Avon Automotive, which cancel 90 per cent of engine vibration at idle. Active mounts use an electronic control system and a powered mechanism to cancel an additional 90 percent of this engine vibration at idle.
A system that can cancel out in excess of 90 percent of engine idle vibration into the car has a huge impact on the vibration levels experienced by the vehicle occupants. This technology, in conjunction with the other noise, vibration and harshness ( NVH ) improvements, ensure that Jaguar delivers class-leading levels of refinement for the XJ's first ever diesel engine.The driver’s airbag is also now isolated from the steering wheel, which significantly reduces the level of vibration transmitted through to the driver. The result is a car that offers best-in-class refinement.
The 2006 XJ range also features a host of new features that are included as standard on all models. Subtle changes to the exterior trim of the car give it an even more contemporary feel while a range of driver aids such as the Tyre Pressure Monitoring System, Automatic Speed Limiter and Bluetooth wireless connectivity that has been developed by Jaguar in conjunction with Motorola and is compatible with a number of current Bluetooth handsets.
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