The AJ-V8 Gen III Engines

Since the first XK was launched in 1948, generations of powerful yet refined engines have played a crucial role in establishing the unique character and pedigree of Jaguar cars. Now, the new 5.0-litre V8 direct-injection engines continue that tradition, delivering increased power and torque with reduced emissions and impressive fuel economy. Available in two versions – the supercharged 510PS and naturally aspirated 385PS – the new AJ-V8 Gen III engines exemplify Jaguar’s reputation for innovation and engineering excellence.

We set ourselves the challenge of developing an all-new V8 engine series that improved on the performance and the refinement of the excellent 4.2-litre, with comparable fuel economy and improved emissions. We have achieved that with the AJ-V8 Gen III – a superbly responsive power unit of unsurpassed efficiency.

Ron Lee, Powertrain Group Chief Engineer

Jaguar’s all-new petrol V8s have been designed using the expertise of powertrain engineers at Jaguar’s product development centre at Whitley, Coventry, UK.

The emphasis was on delivering efficiency, superior dynamic response and highly accessible low-end torque suited to real-world driving, without compromising power at higher engine speeds.

Malcolm Sandford, Engine Group Chief Engineer

The results are clear to see. Performance has been increased by 29 percent and 23 percent (87 and 94PS) on the naturally aspirated and supercharged engines respectively, yet both meet EU5 and US ULEV2 emissions regulations. Despite the significant increases in power, both have better emissions and comparable fuel economy to the previous 4.2-litre units.

Both new AJ-V8 Gen III petrol engines are state-of-the-art in every sense. The technical features have been engineered to deliver unparalleled efficiency, refinement, power and torque for which Jaguar is famous, combined with the lowest possible emissions. Low-speed torque characteristics and throttle response are world-class, while the supercharged version is one of the most economical 5.0-litre V8 engine available.

These engines have been engineered by our 800-strong powertrain team for the next generation of Jaguar cars. They deliver fantastic straight-line performance and response that is second to none. The combination of power, refinement and driveability is what our customers expect of a Jaguar: they are smooth around town, but when you want to drive quickly, the engines are hugely responsive and deliver that classic, Jaguar sound quality.

Mick Mohan, Director, Jaguar Programmes

Light, robust and very strong

The new AJ-V8 engines are built around a stiff, all-new, aluminium block with cast-in iron liners and cross-bolted main bearing caps to reduce noise, vibration and harshness. The blocks are high pressure die-cast, providing a superior finish and greater dimensional accuracy. The engines use aluminium heads, with four valves per cylinder and spheroidal-graphite cast-iron crankshafts and forged steel connecting rods. The cylinder heads for the first time are specified with a secondary (recycled) aluminium alloy thus reducing the environmental impact of manufacturing the new engine.

The new 5.0-litre direct injection petrol engines are more compact than their predecessors. Overall engine length has been reduced by 24mm by relocation of the oil pump within the engine architecture. This length reduction – apparently a small amount – improves engine bay packaging in support of enhanced safety cell performance while ensuring overall engine weight is virtually unchanged.

New supercharger optimises power

A sixth-generation, twin vortex system supercharger is fitted to the XKR’s 510PS engine. It is a compact Roots-type unit, feeding air through twin intercoolers, which in turn are water-cooled by their own discreet cooling circuit. The high helix rotor design improves the supercharger thermodynamic efficiency by 16 percent over its predecessor. It also improves noise quality to the point where the unit is now virtually inaudible (making supercharger whine a thing of the past). The intercoolers reduce the temperature of the pressurised intake-air and so optimise power and efficiency.

The new air intake has been radically redesigned compared to the previous V8. The intake air path is a direct feed to the supercharger inlet from the centrally mounted front throttle body. Air is delivered through twin air boxes, which reduce flow loss and further increase efficiency.

Mechanically, the new supercharger and its intercoolers are efficiently packaged in the ‘V‘ of the engine to deliver a lower overall engine height in support of pedestrian safety requirements.

Direct injection - power with economy

One of the key features of the new petrol engines is an industry-first, centrally-mounted, multi-hole, spray-guided fuel injection system, delivering fuel at a pressure of up to 150bar directly to the cylinder. This substantially contributes to improved low-speed, dynamic response. The positioning of the injectors ensures fuel is precisely delivered to the centre of the combustion chamber, maximising air-fuel mixing and improving combustion control. Fuel is delivered via twin, high-pressure fuel pumps that are driven via auxiliary shaft in the all-new engine block.

The charge cooling effects of the direct-injection fuel system have allowed the compression ratio of the naturally aspirated engine to be raised to 11.5:1, further optimising the engine economy. The supercharged engine also benefits from a compression ratio increase to 9.5:1 from 9.0:1 in the previous 4.2-litre.

During the engine warm-up phase, the combustion system employs multiple injection mode strategies to deliver 50 percent more heat for fast catalyst warm-up and emissions reduction.

Torque-actuated variable-camshaft timing improves efficiency

A new type of variable camshaft timing (VCT) system introduces another new technology. The four VCT units are activated by the positive and negative torques generated by opening and closing the intake and exhaust valves, instead of by oil pressure. This has allowed the engine oil pump to be reduced in size, saving energy and improving fuel consumption.

VCT units work independently on all four camshafts with 62 degrees of authority on the inlet cams and 50 degrees of authority on the exhaust cams. Timing is optimised by the engine control unit for torque, power and economy at every point in the engine’s speed range.

The new VCT units are capable of a response rate up to three times faster than in previous Jaguar engines, with actuation rates in excess of 150 degrees per second. This delivers a more immediate engine response to the driver’s demand for power.

The naturally aspirated engine is also equipped with camshaft profile switching (CPS) on the inlet camshaft. Depending on the engine’s running conditions and the demands of the driver, the CPS will switch between a profile that is ideal for low-speed driving and another which gives increased valve lift for high performance.

Hydraulically-actuated two-piece tappets switch between profiles on the tri-lobe camshaft altering both the lift and duration. The cam lobe profile selected for lower engine speeds has a duration of 214° and lifts the valves 5.5mm. This optimises gas velocity for improved low-speed torque and reduces valvetrain friction for improved fuel economy. For high-speed driving, CPS switches to a cam lobe with a duration of 250° and valve-lift of 10.5mm, allowing greater air flow for high power. Switching is activated at 2800rpm at high load, ranging to 4500rpm at light load conditions.

Variable Inlet Manifold optimises torque through the rev range

A new variable inlet manifold (VIM) on the naturally aspirated engine can vary the length of its eight inlet tracts to optimise power and torque throughout the rev range. Vacuum-operated actuators open valves to select a longer, 680mm, inlet tract at low revs, increasing the rate of both the airflow and the engine torque. As the revs climb beyond 4700rpm, the actuators select a shorter, 350mm path allowing a greater volume of air into the engine to optimise power. The actuator position is monitored by the engine control unit to improve torque throughout the engine speed range.

Reverse cooling turns up the heat

Every component in both V8 engines has been optimised for efficiency, performance, low-end torque and reliability. An innovative reverse-flow cooling system design has been employed to deliver thermodynamic and friction improvements. The reverse-flow cooling system pumps coolant through the cylinder heads before it flows through the block and returns to the radiator. The resulting cooler cylinder heads allow more optimum, knock-free, ignition timings.

In addition, the 22kW oil-to-water heat exchanger, packaged at the core of the engine, transfers heat from the coolant to the lubricating oil during warm up, bringing the oil up to operating temperature 14 percent faster than the cooling system used in the 4.2-litre V8. This improves fuel consumption in the crucial engine warm-up period by approximately one percent - again a small amount, but part of a package of efficiencies.

Reducing friction – something for nothing

Minimising internal friction is key to improving fuel consumption and CO2 emissions, and as such was a key aim when it came to the design of the engines. As a result, the new Jaguar AJ-V8 Gen III engines achieve another best in class, setting a new industry benchmark for cranktrain efficiency.

All engine bearings were engineered for reduced friction without compromising reliability. Diamond-Like Carbon Coating (DLC) has been used to reduce friction on the fuel pump tappets and a solid film lubricant has been used to coat the piston skirts. New engine oil has a lower viscosity, contributing to an extension in service intervals from 10,000 miles to 15,000 miles (or 12 months). Both V8 engines are now fitted with an electronic oil-level indicator for added peace of mind.