V8 Engine

The new engine, Jaguar's first ever V-8, is the latest in a line of innovative, thoroughbred Jaguar engine designs, spanning six decades of engineering excellence. At the outset of the program, the powertrain Design Group at Jaguar's Whitley engineering center in Coventry were given a clear mission: to deliver "refined power" with world class standards of quality and reliability. This succinct objective provided unequivocal direction for the cross functional, dedicated team of engineers throughout the design and verification program. The result is the innovative Jaguar AJ-V8: a compact, rigid, refined and lightweight powertrain comprising a 32-valve, 90 degree, quad cam, all aluminum V8 engine.

The AJ-V8 engine is manufactured in an all new dedicated Jaguar facility located within Ford's Bridgend South Wales engine plant. The Jaguar facility, which comprises a linked flow line of computer numerically controlled machines with automated loading and assembly, has a production capacity of 50,000 engines a year. Component supply is on a "just in time" basis. Final engine dress and assembly into cars is undertaken at Jaguar's Browns Lane plant in Coventry.

The foundation of any engine is the cylinder block. Design of the block structure for AJ-V8 was guided by finite element analysis, while solidification modeling minimized the weight and porosity of the block casting.

The block/bedplate design, which combined with the inherent strength of the compact V8 configuration, minimizes vibration, enhancing engine refinement. In addition, seven grades of main bearings ensure the accurate control of bearing clearances during the assembly process.

The block itself incorporates a cast, ribbed web which links the two banks of the engine high in the Vee, contributing to the high first torsional frequency of 775 Hz. The block is a closed-deck design both for rigidity and to provide a sound face for the head gasket seal.

The cylinder block features Nikasil-plated bores to a thickness of 0.08 MM (0.003") rather than conventional iron liners giving a weight savings of 7 kg (15 lbs) while providing highly wear resistant surface. Nikasil is a pump through electroplating process which deposits a nickel silicon carbide surface coating on the cylinder bores. The resultant bore surface is very smooth, benefiting oil consumption and minimizing piston friction.

The aluminum cylinder heads are manufactured by the COSWORTH low-pressure, sand casting process to ensure highly accurate port and combustion chamber locations and low porosity. Jaguar's classic four vales per cylinder (pictured below), pentroof head design is retained but with an unusually narrow, included-valve angle of 28 degrees. This gives both a compact combustion chamber and overall cylinder head size, minimizing engine width and thus facilitating in vehicle packaging.

The two cylinder heads are unique castings, each with a mirror image of the other, and are offset 18mm. The head is heavily ribbed to optimize stiffness, minimizing radiated noise while providing a sound basis for the head gasket joint. The cylinder head bolt threads are deep drilled for optimum head gasket clamping and minimum bore distortion.

The combustion chamber forms the heart of an engine's gas flow system. During the concept design phase, numerous systems were assessed with varying port and chamber designs and bore/stroke combinations. The one chosen for AJ-V8 is an evolution of the pentroof design found in Jaguar's in line, six cylinder AJ-16 engine and features an extremely compact chamber, made possible by the narrow valve angle and high compression ratio. In addition, the simple open chamber shape with no squish, provides an extremely high volume to surface ratio, optimizing the thermal efficiency of the engine. This results in excellent specific fuel consumption, achieving a minimum of 0.24 kg/k.hr (0.4 lbs/hp.hr).

The compact combustion chamber is very efficient in the use of swirl. Although the swirl level generated by the inlet ports is relatively low, excellent part throttle characteristics are achieved. This provides a good balance between part load fuel consumption and noise at high loads.

The shape of the inlet ports ensures that swirl levels are not affected significantly by casting variably and that fuel wetting of the port walls by the injectors is minimized for consistent engine performance and emissions.

Fundamental to the performance of any engine is its ability to draw air into the cylinders and then to use it efficiently. This demands well designed fuel, air, exhaust and combustion systems. These key systems are the prime determinants of engine power, torque and emissions and also exert a significant influence on fuel consumption.

The AJ-V8's innovative air inlet manifold, molded from polyamide composite, features integral fuel rails for simplified assembly and accurate location of the fuel injectors relative to the cylinder head. The twin spray, side-fed injectors, combined with the insulated plastic manifold, deliver outstanding hot-fuel handling, ensuring excellent starting performance.

The inlet manifold features eight long runners feeding the inlet ports of each cylinder from a central plenum. Tuning of the runners was optimized at mid-range engine speeds, complementing the VCP system, which enhances performance both at low and high engine speeds. The insulation of the manifold also improves power by reducing air temperature.

The paper filter element has a 48,000 km (30,000 mile) service life. The large size of the element (1.48 m2/16 ft2), coupled with careful design of the air cleaner box and intake trunking, minimizes the power loss associated with type of filter.

A 75 mm (2.95" diameter), throttle minimizes power loss while retaining excellent engine control. The throttle is water heater for stable operation in all weathers and to prevent icing. It is mounted to the intake manifold via an adapter which also serves as the mount for the EGR valve, the connection point for the crankcase ventilation system, the fuel purge system and the vacuum takes offs for the brakes among other systems.

The throttle adapter is made from die cast aluminum and is supported by brackets attached to the block. This provides a stable mounting for the electronics in both the throttle and the EGR valve.

The valvegear of the engine has been designed for low weight and durability. With a diameter of 35 mm (1.38") the inlet valve heads are generously sized to deliver excellent high speed breathing. However, with a stem diameter of only 5 mm (0.2"), the valves are also exceptionally light, contributing to a best in class reciprocating valvegear weight of 3.05 kg (6.72 lbs.)

The valves are directly actuated by aluminum flat tappets fitted with top mounted shims, requiring no adjustment for the life of the engine. A single, low stiffness valve spring reduces friction while maintaining a high maximum safe engine speed in excess of 7,000 revolutions per minute.

The four compact SG cast iron camshafts are large in diameter (28 mm/1.1") and therefore very stiff, while the center of the shaft is rifle drilled to reduce weight. The lobes are chilled during manufacture to achieve zero maintenance valvegear, while five aluminum alloy caps retain each camshaft. The cam profile has been optimized to suit the variable cam phasing (VCP) system.

The crankshaft is made of spheroidal graphite (SG) cast iron. Its design was optimized using the Cranfield lumped mass dynamics model to minimize bending movements and torsional effects. The bearings are asymmetrically fillet-rolled for high strength and the 56 mm (2.2") diameter big end bearings are unusually large for increased stiffness. The six balance weights are configured in a "cork screw" arrangement to provide the best possible dynamic balance from the four-throw, five bearing crankshaft.

The connecting rods are forged by the highly accurate Krebsoge powder-sintering technique and are fracture split to separate the cap from the rod. No component balancing is therefore required. This results in an exceptionally strong but lightweight component that needs little machining. Three grades of big end bearings are used to minimize bearing clearance variation in production.

The aluminum pistons are of a short skirt, low friction design and feature a top land depth of only 4.9 mm (0.19") for reduced hydrocarbon emissions. The piston has a flat top to minimize its surface area, while maximizing the engine's thermal efficiency. Careful matching of the piston skirt and ring pack minimizes noise levels and oil consumption.

MANUFACTURING STRATEGY & PROCESS

1. Automated Cylinder Block Line:

The piston bore machining operation incorporates closed loop gauging which feeds back tool offsets to maintain bore diameter accuracy. Diamond coating honing tools are used for finish machining of piston and crank bores. The use of diamonds ensures consistent machining quality and tool longevity. Turret indexing heads maximize productivity while maintaining a compact layout. The automated Nikasil coated cylinder bore plating facility incorporates a sophisticated effluent treatment and chemical recovery process which exceeds the requirements of the European environmental legislation.

Up to seven grades of main bearing are available so that the ideal one can be selected during assembly to maintain the best bearing clearances. Machines measure the cylinder block bore and journal diameter then calculate which bearing to choose, with the correct size of bearing shells presented to the operator.

2. Automated Cylinder Head Line:

The layout of the line enables either left or right hand cylinder heads to be processed randomly while value guides are inserted by an automated machine for high quality. Liquid nitrogen is used to freeze valve seats prior to their insertion, ensuring a consistent fit, while diamond tipped milling cutters deliver both quality and tool longevity. Engine lifting eyes are cast into the front of the ahead to aid handling.

3. Automated Crankshaft Line with Precision Balancing :

All machines are loaded and unloaded automatically via an overhead CNC gantry. The rifle drilled oil feed holes are deburred with 300 bar (4350 psi) high pressure water jets to ensure clean oilways. The precision crankshaft balance correction machine, with automatic crank pin measurement, compensates for connecting rod and piston masses. This makes a significant contribution to the refinement of the finished engine.

State of the art CNC turn broaching machines rough out the crank pin and journal diameters.

4. Automatic Camshaft Variant Recognition :

The camshaft production process includes automatic camshaft variant recognition and part program selection which caters for 12 camshaft specifications. Cam lobes and timing flats are ground on the same chucking to guarantee angular positions. This assists in setting the camshaft to crankshaft positions in engine assembly. The thrust bearing face is precision turned using synthetic diamond tipped (cubic borazon nitride) tooling. The operation incorporates complete post-process gauging with size control feedback for consistent, high quality machining.

5. Automatic Fracture Split Connecting Rods :

The connecting rod line is a mixture of manually and automatically loaded CNC units, transfer and grinding machines. The sinter-forged connecting rods are fracture split automatically to separate the cap from the rod, eliminating the need for joint face machining. Bolt assembly and run down are controlled electronically. Big and small end bores are finish-machined using diamond coated tools with closed loop, post process gauging feedback. Compensation for tool wear and temperature fluctuations ensure that specifications are maintained.

Three grades of big end bearings are used to minimize bearing clearance variation during production. As the rod is manufactured from a precision near net shape sinter forging, no weight correction or grading is required.

6. Electronically Controlled Engine

Assembly and Test :

Individual engine build pallets carry electronic read/write data tags defining details such as position in the build sequence, derivative, bearing and piston sizes.

The assembly flow line utilizes automatic, semiautomatic and manual build stations. The ergonomic design of manual operations ensures the efficient feed and handling of components to reduce operator fatigue, ensuring consistently high build quality.

Critical operations, such as bolt run-down and block to bedplate sealing, are controlled electronically. Both sealant bead width and position are monitored by camera gauges.

All engines are subject to hot run testing to ensure the full conformance of fuel, emissions, oil and water systems with stringent tolerances and guidelines prior to shipment to Browns Lane for installation in a killer Jaguar.

AJ - V8 Primary Specifications:

Configuration: 90 degree V-8

Capacity: 3996 or 243.9 cubic inch

Bore: 86mm or 3.386"

Stroke: 86mm or 3.386"

Stroke x Bore ratio: 1.00:1

Compression Ratio: 10.75:1

Fuel grade: 95 octane

Base horsepower: non Supercharged 290, supercharged 370

Torque: non Supercharged 290, supercharged 387

Redline: 6800

Camshaft: chilled cast iron

Crankshaft: Spheroidal graphite cast iron, five main caps

Cylinder block: Die cast aluminum alloy block and bedplate assembly. DIN1725 alloy block with Nikasil-plated bores SAE-J452 Bedplate with cast iron bearing cap inserts

Cylinder head: Precision sand cast aluminum alloy; LM25TF, fully heat treated. Twin overhead camshafts; chain driven hydrauically actuated two position inlet cam VCP system.

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