FRANKFURT MOTOR SHOW: Tech leap for Range Rover Evoque

Update, September 11: Land Rover advises that Active Driveline will be standard for the Evoque Si4 from its local launch in February next year. It will not be available for diesel variants and Land Rover will disclose pricing for the upgraded range closer to the launch.

When the updated Evoque reaches Australia in February next year it will bring with it the ZF nine-speed automatic transmission and a fuel-saving idle-stop feature facilitated by adopting the new transmission.

But it's another new drivetrain system for the Evoque that is likely to attract the most attention. The sophisticated new system, named Active Driveline, has been under joint development by Land Rover and GKN Driveline since 2009, as part of a broader project to improve drivetrain efficiency in the Evoque.

According to Land Rover's Senior Manager for Driveline Engineering, Steve Mullane, Active Driveline promises to cut parasitic losses by as much as 75 per cent in a typical drive cycle.

In even better news however, the system is also more capable in off-road situations than the Haldex-based system fitted to the current Range Rover Evoque, and delivers 'torque biasing' dynamic properties to overcome understeer or oversteer.

As Mullane explained to Australian journalists in Germany for the Frankfurt motor show, the current system drags down fuel-efficiency, even when the Haldex unit de-couples drive to the rear wheels. Energy is wasted through gear sets, bearings and seals.

"Active Driveline is our response to the challenge of reducing that spin loss, whilst also providing superior traction, improved steering response and greater stability," Mullane said.

It's a complex set-up to explain, but basically a synchroniser can disconnect the prop shaft that takes the drive to the rear wheels from the power take-off unit at the transmission. In the Haldex system, the coupling is located at the rear of the car, much closer to the rear diff, leaving the heavy prop shaft turning continuously, even when there is no drive being sent to the rear wheels.

On the rear axle, two multi-plate wet clutch packs engage and disengage drive to each of the rear wheels. When the car is supposed to be operating in front-wheel drive mode only, the clutch packs act like free-wheeling hubs, decoupling the wheels from the rear diff.

With just the front wheels driven, the Evoque's prop shaft and rear diff are motionless, but the system can re-engage four-wheel drive on demand within 300 milliseconds, Mullane claims. Properly speaking, the rear differential isn't a differential at all, since it lacks the spider gears to vary output speeds to the drive shafts. It's merely a crown and pinion gearset with the clutch packs located either side.

Because the clutches can operate independently of each other, it's possible for the system to brake or lock one or both wheels, which delivers improved off-road traction and better on-road handling. Mullane says that 'torque biasing' can dampen understeer or trailing-throttle oversteer by changing the torque split accordingly. Relatively more torque to the outside wheel will correct understeer, and more torque to both rear wheels will correct oversteer.

Active Driveline comes with a new driver interface that illustrates how the driveline is operating at any given moment. When the vehicle is at rest, the readout in the infotainment screen clearly shows that the synchroniser has coupled the prop shaft in anticipation of traction loss at lower speeds.

But the system moves into its exclusive front-wheel drive state from 35km/h, ready to transfer torque to all four wheels as soon as the system detects a loss of traction or undesirable handling traits. Active Driveline will automatically change mode to all-wheel drive at speeds above 180km/h.

Mullane says that testing of the Evoque with all three fuel-saving features (idle-stop, the nine-speed auto transmission and Active Driveline) has revealed efficiency gains of up to 11.4 per cent.

Here's the full run down on the latest news from Frankfurt motor show

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