Vehicle Development – Automotive Engineer

7 May 2015 | Author: | Comments Off on Vehicle Development – Automotive Engineer

Land Rover Defender

Land Rover has been producing its original all-wheel drive model since 1948

A midlife facelift is usually enough to squeeze six years from a vehicle before the replacement model is launched. So it’s remarkable that Land Rover has been producing its original all-wheel drive model since 1948 with so few changes.

It’s regarded by many as the toughest, most capable off-road vehicle ever made. There’s still a need for a basic, uncompromising 4×4 but the luxury SUV market – pioneered by the Range Rover – is far more lucrative. And the weight of a ladder frame chassis like the Defender’s makes development for stringent emissions and safety laws much harder.

“For Euro 6 you’re getting to such low levels of emissions that we’d have to do a lot of re-engineering to the vehicle architecture,” says Gary Taylor, chief programme engineer for the Defender. “When it gets to that you’d say that you wouldn’t start with this platform – so you have to look at other things.”

Which is why the latest version will also be the last. A Euro 5 diesel engine and improved NVH levels are enough to keep it going until its replacement – based on the DC100 concept – appears in 2015.

The 2.2-litre diesel, developed from Ford’s Puma commercial vehicle engine, replaces the former 2.4-litre unit. Output is the same but changes to the compression ratio, fuel injection and aftertreatment make it cleaner and quieter. Packaging the diesel particulate filter (DPF) meant changing some of the footwell pressings but allowed it to be close-coupled, improving light-off times.

Duty cycles are harsh, though – many vehicles will not see the high-speed cruising that typically purges DPFs of soot.

“Because we’ve got the DPF so close to the manifold, the gas temperatures we get in there mean that the vehicle can run at much lower speeds and for shorter periods during regeneration,” says Taylor. “We can do it at around 30km/h, so it should be durable. We’ve done a lot of work on oil dilution to understand the long-term implications of that.”

Revising the 1,800bar commonrail system, supplied by Continental, and adding an acoustic engine cover reduces NVH considerably. Improving panel gaps and applying sealant before the body goes through the paint shop contributes to lower cabin noise levels.

Apart from these differences, the vehicle is much as it was. This has been the approach for years: change only what’s necessary for legislation. Most consumers like the vehicle the way it is.

Margins are lower than on the Land Rover Discovery. It’s difficult to recover investment on a vehicle made in volumes of around 20,000 units and many variants.

The DC100 concept, or programme 660 as it will be known in series development, has been shown in two derivatives but consumers who bought Defenders may want a wider choice. That will be difficult if the new vehicle’s built using a monocoque platform. Land Rover must also decide what target attributes to go for.

That’s not much of an issue for the Defender because it’s really an off-roader you can drive on the road when you want to. The reason it’s so good in rough conditions is the basic architecture, which delivers lots of ground clearance and axle articulation.

“You could argue it’s compromised for on-road capability because it was designed for off-road, with centrally mounted A-frame suspension,” says Taylor. “If you wanted to design a car that was going to handle more optimally you probably wouldn’t go in that direction.”

Most Defenders come in two wheelbases: 2,360mm and 2,794mm, or 90 and 110 as they’re called – it’s the dimension in inches. Taylor says that Land Rover’s research shows that 100in is the optimum to get the best approach and departure angles. At 2,574mm, the DC100 matches this almost exactly.

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