Slick technology boosts grip in new Cayenne

Porsche's second-generation Cayenne, launched earlier this week, brings with it high levels of technology to aid the driver. Specifically, we're talking the kind of gadgets that aid driving, whether on tarmac or trail.

PDCC, Porsche Dynamic Chassis Control, is standard on the Cayenne Turbo. The basic idea dates back a while and some may recall the Citroen Xantia Activa with an active roll-control system as long ago as 1998 -- but Porsche's execution is different again.

PDCC is standard for the Turbo, optional for all other variants. The system, operating at both the front and rear of the car, relies on hydraulic swivel motors to adjust roll control in accordance with steering angle and lateral acceleration. A switch provides the driver with the means of manually disabling the system for offroad operation.

"The hydraulic pressure and flow rates in the chassis stabilisers stiffens or softens the stabiliser and prevents the body from [adopting] a higher inclination rate," explained Stefan Fegg, Project Manager for Cayenne Powertrain.

PASM, Porsche Active Suspension Management, provides three different suspension damper settings: Comfort, Normal and Sport. In the new Cayenne, this system is available as standard for all models -- irrespective of whether the car is fitted with steel springs (base model V6 and diesel) or standard air suspension (Cayenne S, Hybrid and Turbo).

PTV Plus, Porsche Torque Vectoring, is a safety feature that has been introduced to this market in other cars. In coordination with PTM and PSM (Porsche Stability Management -- effectively Porsche's own name for electronic stability control), the system monitors steering angle and speed, the amount of throttle, yaw rate and road speed. If necessary, the system will individually apply brake pressure to the rear wheel on the inside of the corner. Through the rear differential, more torque is transferred to the outside rear wheel, enhancing the vehicle's steering response.

PTM, Porsche Traction Management, obviates the need for a dual-range transfer in this generation of Cayenne, claims the car manufacturer. Doing away with this offroad feature cuts out as much as 33kg from the car's overall weight, Porsche says. PTM has actually been developed for two different applications: Diesel/Hybrid variants and the sportier models.

While the two fuel-sippers are equipped with a self-locking centre differential, the base model V6 and the two V8 variants come with an active all-wheel drive system based around an electronically-controlled multi-plate clutch system. PTM ensures that torque is transferred from rear to front axle in the event of wheelspin and it works in combo with an Automatic Brake Differential (ABD) on the front axle. We've seen the ABD demonstrated in an offroad situation at Brisbane's Mount Cotton Training Centre -- and came away impressed.

As Porsche Training Manager Paul Watson explained it, if the front wheel on one side is raised and has lost traction, the ABD brakes that wheel and there's only one other place for the torque to go -- through to the diff to the wheel firmly on the ground. The ABD and PTM allow initial slip (but not much). After that, the Cayenne just grips and goes.

PHC, Porsche Hill Control, was another feature demonstrated at Mount Cotton. Much like most other similar systems, it holds the car's speed to a manageable level on downhill grades without the driver needing to apply the brakes. Unlike other systems, it can be programmed manually for a very low ceiling speed through the car's cruise control system, according to Watson.

Three offroad modes are available in the non-hybrid Cayenne variants. Offroad Mode 1 recalibrates electric aids like ABS on the fly, to operate in a way consonant with bush bashing. It also enables PHC. When enabled on cars equipped with air suspension and PASM (see below), Offroad Mode 1 automatically raises the car's suspension to 'offroad level'. The driver can manually adjust the suspension higher still, if desired. In this mode, the automatic transmission adjusts shift points to suit offroad work and locks out the kickdown facility, even if the driver presses the accelerator all the way to the floor. The damper clutch that mechanically locks up the gears in the transmission will not operate in this mode.

In Offroad Mode 2, the multiplate clutch in the Cayenne's drive system is locked, ensuring an exact 50/50 torque split from front to rear. When specified, the optional PTV facility (see below) that electronically controls torque through the rear axle, changes mode from on-road to an offroad frame of reference, ensuring torque is shared with the left and right rear wheels for optimum traction. If the driver selects Offroad Mode 3, the rear differential is locked completely.

The Adaptive Cruise Control option, as in other cars equipped with the feature, will automatically hold the Cayenne at a safe braking distance behind other cars, even when they reduce speed on the freeway. Unlike most other cars so equipped, the Cayenne's system will bring the Porsche to a full stop. We asked Paul Watson wether there were any legislative obstacles that had to be overcome before this system could be introduced to the Aussie market.

"No, it puts the brake lights on, so no, it's fine," Watson explained. "The only legislative problems we have to go through is to make sure that the radar system works in the right spectrum. It runs on a radar system, so we have to have licences for the radar frequencies that we're running -- as all manufacturers that run the system do."

In the event that the driver of a car in front slams on the car's brakes, the Cayenne's cruise control system will brake at a rate of 0.8G, which Watson describes as: "a reasonably substantial braking effort... but after that, you need to take over."

Lane Change Assistant comprises radar sensors facing obliquely to the rear and covering the blind spot around the C and D pillars of the vehicle.

"It will give you an indication of a car coming up on either side of you," says Watson. "It has radar sensors in the back and if there's a car closing in your blind spot, it will warn you. If you don't have the indicators on, it gives a light flash of a warning light in the rear-vision mirror to tell you; if you put your indicator on, it gives you bright flashes of that same set of warning lights and multiple times -- to warn you someone is coming up beside you and you've indicated you want to move into that lane."

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