AJV8 Engine 1996 – Present
The first production V8 from Jaguar replaced both the 6-cylinder AJ16 and the V12 engines at its launch in the XK8 in 1996. The engineers at Jaguar had flirted with V8 configurations in the past but it was not until the 1980s, under Ford management, that they could proceed with such a powerplant. The AJ6/16 and V12 were proven designs but Ford had a vision for a series of V-configuration engines, which included a V6 and a V12. The new programme was given the designation AJ26, and although the three configurations were explored, it was the V8 that took over as the lead design. This took shape as a Double Over Head Camshaft (DOHC) 90-degree unit of 4.0 litre capacity and by 1990 the Ford and Jaguar boards had given approval for the unit to be produced. Ford assigned a dedicated building at their Bridgend plant, in Wales, to manufacture the Jaguar “AJ-V8”. This decision meant the closure of the engine plant at the former Daimler works at Radford in Coventry.
Trevor Crisp and David Szczupak led the team which made the V8 into a compact unit which, though wide, would fit comfortably into the existing X300 saloon and its proposed successor. It would also fit into the sports car then in design from Fergus Pollack, Keith Helfet and Geoff Lawson. Jaguar’s new V8 was ground-breaking by being a mainly all-alloy unit, which kept weight down to a minimum. The engine also featured: fracture-split forged powder metal connecting rods, a special one-piece cast camshaft and a reinforced Polyamide composite plastic intake manifold, which was light and provided external thermal insulation. This enabled Jaguar to accommodate an integral fuel rail into the manifold, reducing complexity and improving injector targeting.
Interestingly, the Jaguar engineers stayed with the valve operation system they knew best, having already used it with previous engines. This meant direct operation with aluminium bucket tappets beneath the cams with shim clearance adjustment. Proven chain-drive for the camshafts was chosen – years of experience with the XK showed this was more efficient than belts – but variable timing actuators were fitted to the inlet camshaft sprockets. Jaguar chose ‘Nikasil’ plated, rather than lined, cylinder bores. Once in production it was found that the plating was subject to attack from low-grade, high-sulphur, fuels and some engines had to be replaced under warranty. The plating was later replaced with thin-walled steel linings. The twin cylinder heads were produced by Cosworth exclusively for Jaguar.
A substantial aluminium bedplate, carrying the cast sump, was used to close off the lower end of the engine block which gave the bottom end great strength. The five-bearing crankshaft itself was made from spheroidal graphite cast iron, rather than steel, making it immensely strong. A new, Jaguar patented, split coolant flow, from the water pump, delivered 50 per cent of the coolant into a gallery, bypassing the bores, to the cylinder heads at the rear of the engine. This then mixed with the remaining 50 per cent of the coolant to cool the bores. This proved efficient and gave the AJ-V8 a fast warming-up time of under four minutes.
Work continued on testing the AJ-V8, in modified XJS sports and X300 saloon models, and by 1996 the trials were over and the engine ready for production. The unit had taken three years, and cost some £200 million to develop, by the time it was introduced in 1996 in the XK8 sports car. This gave Jaguar a new image and one that made up for the years of wilderness under British Leyland. Production commenced in May 1996 and within a month some 35 units were being manufactured daily.
Having supercharged the AJ6/16 engines for the XJR in 1994, it was natural that the AJ-V8 was given the same treatment. Jaguar found that the V8 was an excellent platform for adding the Eaton M112 supercharger. Engineers at Jaguar thought long and hard about supercharging against turbocharging. They decided the former was better because it provided immediate response to throttle openings and achieved high boost levels at low and medium speeds without the ‘Turbo-lag’ which is present in the alternative.
For the supercharged AJ-V8, new dished pistons (instead of flat topped) were fitted for a revised 9:1 compression ratio. The pistons of high strength aluminium alloy were designed to resist high thermal and mechanical loads of the supercharged engine. Other changes included: new crankshaft damper; new inlet cam sprocket (for the 3.2-litre); new cylinder head gasket featuring stainless steel bore eyelets in place of mild steel; new intake system; new cooling pipes and new resonators to improve air intake. Running at 1,600 rpm the supercharged AJ-V8 was producing more torque than the naturally aspirated AJ-V8 at its optimum. The supercharged engine did not use variable cam timing as the normal benefits of improved volumetric efficiency were not noticeable on the boosted engine.
Ford US adopted the AJ-V8 in 3.9-litre form for the 2000 Lincoln LS8 and in 2002 for the new Thunderbird; these engines were given the design code AJ35 and were manufactured in the USA. When production of the AJ35 ceased in 2006 some 250,000 examples had come off the line.
In the UK in 2002, for the second generation AJ-V8, capacity was increased to 4.2-litres by increasing the stroke and reducing the diameter of the crankpin journals to maintain the same block height. This engine was fitted to the XK8 and a 3.5-litre variant was announced for the XJ8.
A further-developed Jaguar version of the AJ-V8 was introduced for the XJ8 (X350 in 2004) XK (X150 in 2006) and the XF of 2008. A revised supercharged engine was also introduced for these models. Having Land Rover in the stable meant the AJ-V8, in an adapted form, could be used for the Range Rover; initially as a 4.2-litre but in 2005 as a 4.4-litre, which was also used in the Land Rover Discovery.
Aston Martin, then part of Ford, hand-assembled in Germany a 4.7-litre variant of the AJ-V8 with many changes for their Vantage model.
Jaguar has continued to develop the AJ-V8 – naturally aspirated and supercharged – and currently the latest Gen III version (AJ133) in 5.0-litre form is used in the XJ, XF and the F-Type; also the special edition Project 7 uses the engine as do the Range Rover and Discovery models.