The materials innovation that make the XE saloon Jaguar's most important car yet

This, the aluminium intensive XE, is arguably the most important car that Jaguar has launched in its 92-year history. There have been more iconic, notably the E-Type, but it's fair to say Jaguar's future hinges on this new mid-size saloon poised to take on the might of German rivals like the BMW 3-series, Audi A4 and Mercedes-Benz C-class.

But there is more to the XE than that. It represents a turn round in British automotive engineering and manufacturing and a faith in its homeland ability to design, engineer and manufacture cars that bear scrutiny against the best in the world. It stands alongside transplants from Nissan, Toyota and Honda or the Mini's revival as an affirmation that the UK is, once again, a centre for automotive manufacturing and engineering excellence equal to any.

However, to make an impact against its Teutonic rivals, Jaguar's management has taken the bold move to offer a car brimming with technological innovation. It is rare these days to launch a completely new car, but Jaguar has had the confidence to do just that: aluminium intensive body structure, a new engine range, new suspension, even the transmissions have been given a thorough overhaul and update.

Parent company, TATA, has invested £1.5billion in the project creating 1700 new jobs and erecting a new 160,000m2 production facility at its Lode Lane site that will see a vehicle appear every 78 seconds at maximum production capacity. And at 85,000m2 the aluminium body shop is the largest in Europe with 613 robots and unique 'Trunnions' developed with the Expert Group to hold bodyshells in place while riveted.
Jaguar's lightweight challenger

The Jaguar XE, known internally as project X760, is based on a completely new platform (the D7a) that will underpin future generations of both Jaguar and Land Rover products.

At just 251kg, JLR believes the bodyshell is the lightest in its class and it features a number of material advances over other aluminium vehicles from Jaguar Land Rover.
Foremost is the first application of RC5754 aluminium alloy developed with Novelis as Dr Mark White, chief technical specialist lightweight vehicle structures explained:
"We will be generating a lot of processed scrap in higher volumes with this car and we will be getting end of life vehicles starting to come back in 5-10 years time so we decided to take the pioneering step towards full closed loop recycling including aftermarket scrap. RC5754 is the first of a highly recycled alloy used in automotive application and we will go on to develop more."

Novelis supply the sheet metal for the bodywork including 6000 series which has allowed Jaguar to reduce material thickness from 1.5mm to 1.1mm resulting in a 27% weight reduction with no loss in strength or durability. AC300T61 is used in the front crash structure with Sapa, Hydro and Constellium providing extrusions, Magna the shock tower castings whilst Meridian supplies the magnesium cross car beam and front end carrier.

The XE is not 100% aluminium, and features steel closing panels for the doors and deck lid and the rear boot underfloor.

Dr White said: "This was to achieve perfect 50:50 weight distribution with a low centre of gravity for refined ride and class-leading dynamics."

The 'A' posts are purely a sheet based design all using 6000 series and a combination of AC600 and AC300T61 in major crash structures.

Dr White is particularly pleased with the 'B' posts which comprise of a combination of aluminium, steel and structural foam to effectively form a sandwich structure to achieve side impact performance.

Dimensionally, the D7a underpinnings will form the basis of both future Jaguar and Land Rover products; the dimension from the front bumper to the back seat heel board remains the same, with hard points like the sills, front and rear suspension points remaining constant. However, it would be possible to reduce the rear floor's length as well as make the vehicle taller. Although the width is stable it would be feasible to 'cheat' by making the sill thicker.

XE is 20% stiffer than the XF body with what Dr White described as, "good modal separation between body and powertrain," and 70% of the materials are high strength alloys with the remaining 30% 5000 conventional grades.

The big challenge for Dr White and the manufacturing team was to develop systems that would make assembling an aluminium body-in-white almost in the same time as a conventional spot welded steel body-in-white, and at 78 second cycle time, Dr White believes Jaguar has achieved that.

Getting the riveting cycle down to sub 2 seconds was the key and that has been achieved by developing with Henrop more flexible rivet guns that can feed more than one rivet, switching from hydraulic to electric guns, which are quicker and more precise, and blow feeding the rivets rather than using a tape system. "We've gone from 6 seconds per rivet to 1.5 seconds," said Dr White. "To put that into perspective the original aluminium XJ's cycle time was four and half minutes, the XE is 78 seconds."

In total 2772 self piercing rivets and 455 guns are employed in production. Each car is bonded using 115m of structural adhesive which, although they haven't changed in composition, are now applied from heated barrels, lines and dispenser to achieve the correct viscosity time and temperature performance that was needed with the adhesive used between the steel and aluminium acting just as much as an isolator as an adhesive.

"We know that other cars in the future will have a lower cycle time, but we think that XE is pretty much state of the art," he said. "It's about the number of rivets you can put on in a cycle. Getting the riveting down to less than 2 seconds and, depending on the station, can put in anywhere from 6 up to 30-40 rivets."

The lightweight theme is continued elsewhere in the car from its all-new Ingenium alloy-block four-cylinder engine to the modular front double wishbone suspension and integral link rear axle, a first in the size sector.

Slippery customer
With a Cd of just 0.26, XE is the slipperiest production Jaguar to date with its aerodynamics wholly developed using Computational Fluid Dynamics that assisted development of a smooth underfloor running from the front spoiler to the rear diffuser that equalises airflow over the car.

CFD also helped reduce wheel rotation losses with airflow guided into the front wheel arches via the front spoiler intakes and 17-inch aerodynamic wheels. The more powerful models will also benefit from integrated brake cooling scoops mounted to the front suspension that direct cooling air to the front discs as well as active cooling shutters that open and close according to vehicle speed and engine temperatures.

Patents place
Merging the engineering departments of Jaguar and Land Rover has resulted in some interesting crossover of ideas and technology, not least of which on the XE is the, again, patented All Surface Progress Control (ASPC) which was born out of Land Rover's Terrain Response technology. Albeit much simplified for this two-wheel drive application but functions like a low speed cruise control under slippery conditions when traction is minimal.

The driver simply sets the speed and the car's engine management system will deliver precisely the right amount of power to deliver optimum traction for the conditions without the driver needing to operate the throttle, simply concentrating on steering.

Meanwhile the Ingenium petrol and diesel engines, it is claimed, have some 20 patents pending, many in software and control algorithms but also a mechanical one designed to reduce noise from the timing chain driving the high pressure fuel pump. To change the sinusoidal input, Jaguar engineers distorted the fuel injector drive sprocket into an oval by just 0.5mm to eliminate unwanted noise.

Ingenious Ingenium
JLR is gradually weaning itself away from its Ford and PSA engine partners, the first step of which is its £500million plus investment in a new 100,000m2 engine plant that will see a derivative of the Ingenium family launched every 3 to 6 months for the next two years before, eventually, the factory will produce an engine every 39 seconds.

The first engine to be revealed is a 99g/km of CO2, 2-litre, 4-cylinder diesel. Both petrol and diesel engines are based on a common 500cc cylinder capacity with key parameters such as bore centres, deck heights etc. shared allowing all derivatives to go down the same production line; in fact, JLR claim a 30% commonality between the petrol and diesel engines with items such as the balancer shaft and cam shaft needle roller bearing common, although the shafts themselves will be unique. Whilst the common bore size allows them to add or subtract cylinders as needed.

Ingenium has also been future proofed for cylinder deactivation, variable inlet camshaft timing and hybridisation.

Author
Ian Adcock

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Do you have any comments about this article?
The article is exactly what I was looking for and answered a lot of my questions. Regarding the use of aluminium alloys, used in modern motor car assemblies. These techniques are contributing greatly to the vehicle efficiency by reducing the loadings on the chassis and bodywork due to the material weight saving.

Comment Barrie Jones 20/10/2015, 20/10/2015
Very interesting and well written, we are a supplier to JLR, they are doing everything right under TATA ownership and we are proud to be involved. Including the 2 F-Types I have

Comment Gary Knight, 17/12/2014
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