Powertrain: The Efficiency Of Diesel And The Style Of Jaguar - A Unique Combination
The X-TYPE’s first diesel engine arrives in the Jaguar range with a strong pedigree already established. The key to this is Jaguar’s position as part of Ford Motor Company’s Premier Automotive Group, which also comprises Aston Martin, Land Rover and Volvo. The new Jaguar engine, designated internally as X404, is based on the Ford Motor Company four-cylinder TDCi engine. Already highly regarded in its Mondeo application, for the X-TYPE this engine has been further developed to suit Jaguar characteristics. Key to the changes made are reduced noise and optimised refinement and driveability.
The programme to achieve very low noise levels focused particularly on interior cruising- and idle-speed noise levels. Jaguar’s targets were met by optimising the noise reduction benefits of common-rail injection and incorporating other special noise-reduction components to reduce transmission of mechanical and combustion noise.
In calibrating the X404 engine specifically for use in the X-TYPE 2.0D, Jaguar’s engineers used new software tools for the first time to balance the maximum spread of advantage with the minimum need for compromise – in the shortest possible time scale.
Minimum maintenance was another project goal. Success in this area begins with the use of high-durability components and state-of-the-art materials that allow service intervals to be set at 12,500 miles (20,000km) or 12 months. The life of individual components is extended to allow those long service intervals and reduce the overall cost of ownership. Precise fuel metering (provided by an electronically controlled injection system) improves combustion efficiency to the benefit of both performance and economy. This high efficiency has further benefits in reducing emissions: the X-TYPE diesel’s official CO2 emissions rating is only 149g/km, which is a best-in-class figure compared with direct rivals like the Audi A4 1.9 TDI, the BMW 320D and the Mercedes C220 CDI. In the UK, this rating places the X-TYPE 2.0D in the lowest diesel company car tax band.
Developing peak power of 130ps (128bhp DIN) (96kW) at 3,800rev/min and 330Nm (243lb ft) peak torque at only 1,800rev/min, the X404 engine is ideally suited to a sporting premium car. It also offers the facility for short periods of turbocharger ‘overboost’, briefly raising available torque to a maximum of 350Nm (258lb ft).
Perhaps even more importantly, the X404 engine spreads its torque and power very evenly across a broad rev range. On the road, in 'real world' driving situations, the benefits of this are felt in strong and linear mid-range performance, crisp responses, and deep reserves of torque for safer overtaking.
The way in which the engine has been installed in the X-TYPE was the subject of a major upgrading programme. From the outset, Jaguar engineers considered it vital that Jaguar’s first diesel X-TYPE should sound as quiet and refined from outside the car as it does from the inside. This necessitated the development of new packaging solutions, and as with the engine revisions themselves, Jaguar supplemented its own expertise by consulting acknowledged expert Ricardo, a world leader in diesel engine design and development.
Wider design objectives of the programme – in addition to achieving Jaguar levels of performance, driveability and refinement - included low cost of ownership, outstanding fuel economy, low maintenance costs, long-term durability and extended service intervals.
It is only right to acknowledge that the achievements in developing the X-TYPE diesel engine were largely made possible by the starting point being the turbocharged Ford Motor Company 2.0 litre TDCi diesel engine. The in-line four-cylinder engine is light, compact and strong. Including the flywheel and clutch assembly, the engine weighs only 195kg (430lb). It is just 503mm (19.8in) long, 608mm (23.9in) wide and 681mm (26.8in) tall.
With a capacity of 1,998cc, from classically ‘square’ bore and stroke dimensions of 86.0mmx86.0mm, the engine features lightweight construction and a very stiff cast-iron block with aluminium ladder frame. An aluminium alloy cylinder head with a separate aluminium alloy camshaft carrier assembly also features, as do double overhead camshafts driven by a duplex chain that also drives the high-pressure fuel-injection pump. The camshafts operate four valves per cylinder (two inlet and two exhaust), through large diameter roller rockers designed for low friction and long life. Each camshaft is a fabricated component with sintered cam lobes – again for long life.
The crankshaft is forged steel, with five main bearings for strength and durability. It uses eight counterweights (two per cylinder) for excellent balance and smooth running. Lightweight aluminium alloy pistons give high performance, and the sinter-forged connecting rods use fracture-split big-end journals for lightweight and precision fit.
The fuel system combines very high-pressure common-rail direct injection with a variable-geometry turbocharger and a charge-air intercooler. This has been developed in Jaguar’s adaptation of this engine and adds instant throttle response to the engine's appeal.
An engine-driven, dual-stage vane-cell type fuel pump draws diesel from the tank, via a fuel filter. It delivers the diesel at very high pressure to the ‘common-rail’ which supplies the individual injectors. The common-rail is essentially a forged steel tube capable of withstanding pressures in excess of 3,000bar, (45,000psi), with four outlets, each feeding a separate fuel injector nozzle. For the X-TYPE X404 engine, Jaguar chose a ‘short-nozzle’ head design and new short-nozzle injectors that make the engine quieter and improve refinement.