New Range Rover joined by Sport

  • 17-May-2013 09:31 EDT
Range Rover 05-13 Torque Vector.jpg

Torque vectoring is a major element of the new Range Rover Sport's sophisticated chassis systems.

A number is being applied to Land Rover’s new Range Rover Sport that initially is difficult to understand: 75% of its components are different from those of the regular Range Rover, itself new for MY2013.

The two models share the same PLA aluminum platform, they are structurally very similar (but the Sport has a third row of fold-down seats to provide a 5+2 configuration), and both claim to be some 420 kg (926 lb) lighter—the best Sport figure is 2114 kg (4660 lb)—in terms of curb mass than the previous-generation cars.

So, 75%? “Absolutely,” said Stuart Frith, Chief Program Engineer for the Sport. It all adds up in terms of part numbers and what they identify in terms of achieving the new-generation Sport’s requirements—notably agility, handling, and response to driver inputs.

There is more in prospect, with a four-cylinder engine and a hybrid using a diesel engine for optimum CO2 levels scheduled. Later this year a V8 diesel with maximum torque of 700 N·m (516 lb·ft) will be added to the engine range.

The Sport will be launched internationally this fall, initially with a choice of 3.0-L V6 turbodiesel and V8 supercharged 375-kW (503-hp) 5.0-L gasoline power units. An eight-speed ZF automatic transmission is used for all Sport versions.

In its V8 gasoline form, the new Sport is the fastest and most responsive ever production Range Rover, said Frith: “Less than 5.0 seconds to 97 km/h, and that performance comes with 30% better handling, 30% better ride quality, and 15% better steering feel than the previous generation Sport. Saving so much weight will allow us to get the same performance from an inline four-cylinder engine as a V6 and have a curb weight of less than 2 tons.”

Frith is particularly pleased with the Sport’s dynamics: “We tried to push the boundaries of physics as far as we could.”

The car gets a new Dynamic Response System with faster acting rear differential, significantly changed and recalibrated electric power assisted steering (EPAS), and a control system that is also faster. The fully independent suspension is lowered 8 mm (0.3 in) to maintain the camber and caster angles necessary for tire performance. Large parts of the (primarily aluminum) suspension were retooled including arms and knuckles. All this, together with some styling changes that make it pleasantly more subtle, gives the Sport a notably different character to the regular Range Rover.

“We have changed arms, knuckles, links, bushes, active anti-roll bar system, and fitted new steering hardware,” explained Frith. “The steering has more responsive on-center feel without making the car too nervous in [the] straight ahead. Use of torque vectoring is also significant and includes a fast-acting rear electronic differential supplied by Dana. Air springs are stiffer, and the whole handling balance is altered to create a greater feeling of dynamic ability.” Dampers and bushes are stiffer, too.

However, Frith said that the lower ride height and dynamic tuning had not prevented the Sport from achieving what he terms “class-leading” maximum total off-road articulation, at 546 mm (21.5 in) or 52 mm (2.0 in) better than the previous Sport—essential for very tough terrain travel.

The two-channel active anti-roll system controls front and rear axle roll rates independently to provide low-speed agility and high-speed stability.

“The driver-selected Dynamic Response mode activates a unique set of calibrations for a wide range of chassis systems,” explained Frith. “It is not just another ‘sport’ setting; it significantly reconfigures the chassis—the torque vectoring (monitored via yaw sensors to detect understeer) becomes slightly more aggressive—and powertrain more responsive.”

Torque vectoring is an aid on road, track, and off road. On a track, it helps the Range Rover Sport drift by “rotating” it into a corner but has been designed to then immediately “blend in” to maintain stability without the driver having to modulate the accelerator pedal, stated Frith. Various chassis settings are available for specific off-road conditions; in “snow” mode, torque vectoring backs off by 15% and in “sand,” increases by 15%.

The electronic differential, complementing the torque vectoring system, incorporates a multi-plate clutch, responding in 180 ms.

The Sport has a choice of two 4x4 systems with either a single- or two-speed center differential. The two-speed unit provides low range for off-road work and can direct up to 100% of torque to the rear axle. High gives a 1:1 range; low 2.93:1. High and low can be selected at speeds up to 60 km/h (37 mph).

The Sport uses BWI’s latest air suspension and lightweight active roll-control actuators. The air suspension gives 185 mm (7.3 in) of adjustment, and wading depth is 850 mm (33.5 in).

“A vehicle with such a wide range of requirements is a real challenge for chassis engineers as we can’t accept any of the compromises normally required to deliver excellence in one specific area of capability.” said BWI’s Director of Engineering, Doug Carson.

BWI collaborated with Firestone to develop a new type of air sleeve for use in the air suspension modules. This used a special nylon-reinforced rubber compound with a wide temperature range performance. Wall thickness was reduced to cut hysteresis. A focus was also placed on reducing friction in the system. Aluminum was used for a restraining guide to sheathe the air sleeves, giving protection in off-road conditions. Weight was also saved. A particular gain provided by the system upgrades was ride quality over small surface irregularities.

The BWI-supplied Active Stabilizer Bar System includes ball-screw rotary actuators to provide roll control torque to as much as 1500 N·m (1106 lb·ft). Vehicle roll is almost completely prevented up to 0.4-g cornering. As corners are taken and forces detected, the front and rear actuators apply a counteracting rotational torque to the vehicle’s chassis via the cast lever arms of the stabilizer bar system. Independent control of the front and rear roll stiffness allows real-time optimization of the oversteer/understeer characteristic, improving turn-in, safety, and comfort. The actuators facilitate a 134° rotation compared to 90° for BWI’s previous-generation system.

Carson adds that the very high angular articulation enhances packaging flexibility, allowing a compact architecture. Mass has been reduced by 2.4 kg (5.3 lb) front, 2.2 kg (4.9 lb) rear, mainly by the use of BWI-supplied hollow torsion bars with cast splined lever arms.

Tested briefly at Jaguar Land Rover’s Gaydon, UK, proving ground, a pre-production version of the Range Rover Sport demonstrated the beneficial effects of the vehicle’s new technology—notably its steering responses and flat ride—definitively separating it from the softer, more luxury-focused regular Range Rover, and demonstrating that the word “Sport” is not a misnomer.

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