Holden Adventra: AWD system revealed

HOLDEN has revealed technical details of the electronic traction control-based all-wheel drive system that will underpin a swathe of new vehicles, starting with the Adventra cross-over wagon that goes on sale on October 17.

Called Cross Trac, the system has taken more than three years and $50 million to develop, while the total program cost of the Adventra and the Cross8 four-wheel drive Crewman that follows soon after it, is $125 million.

Adventra will beat Ford Australia’s first cross-over, the Territory, to market by around nine months. The $500 million project is tipped to have a mechanical AWD system.

Cross Trac has been designed to underpin performance-oriented road cars as well as cross-overs and commercial vehicles.

Some of the technology will also apply to locally-built rear-wheel drive Holdens.

Cross Trac software is based on a system developed for the General Motors Hummer H2 program and has been modified for use in Australia.

It is a permanent system which transfers torque 62 per cent to the rear wheels and 38 per cent to the front wheels. It does not include low range.

New hardware includes an adaptor housing, three-gear transfer case, front propshaft, front driveshafts and front and centre open diffs. Of these new bits, only the adaptor housing is not manufactured by Holden.

The engine cradle, beefier front suspension lower control arms, larger front brake rotors and new brake pads, oil pan and internal plumbing and rear propshaft are all new as well.

Modifications have been made to the steering rack with revised valving, while the rear axle crossmember has been substantially revised.

For the moment, Cross Trac is combined only with the 5.7-litre Gen III V8 engine and 460LE GM automatic transmission. It will be made available with the new HFV6 engine after it comes on line next year.

Cross Trac employs Automatic Brake Differential (ABD) software to control wheelspin under acceleration and Electronic Brakeforce Distribution (EBD), that works in conjunction with the ABS and Cornering Braking Control (CBC) to provide maximum braking force.

Holden says it had the family driver in mind when it came to designing Adventra, eschewing true mountain goat ability so that it drove in a very similar fashion to the rear-wheel drive Commodore wagon it is based on.

"It was to be an integrated V8 vehicle that would operate seamlessly, as far as the driver was concerned, in a very predictable and controlled manner," said Cross Trac engineering program manager Grant Jamieson.

"The mechanical bias we therefore selected to produce the required definitive Holden vehicle character was rear-wheel drive, power oversteer."Mr Jamieson revealed the Adventra has a minimum 205mm ground clearance and minimum 1940kg kerb weight. An extra 20mm suspension travel has been added at the front and 16mm at the rear compared to the standard wagon.

Local tuning 'an advantage'

ADVENTRA and the Cross Trac system were compared against a number of European all-wheel drive wagons, including the BMW X5 and Audi Allroad, and Holden argues that local software tuning gives its product a distinct advantage.

"The ingenuity of the Cross Trac system is in the detail, particularly in the way it has been calibrated to cope with deformable road surfaces, such as sand, gravel and loose dirt, that are typically encountered in Australia," Mr Jamieson said.

"Sixty-five per cent of our roads are unmade, whereas in Europe they’re overwhelmingly bitumen and often wet and icy. Cars react very differently on dirt-based tracks than they do on hard, wet, surfaces."Unlike most AWD systems, Cross Trac does not cut engine output when wheel slip is encountered, enabling it to run full engine torque when needed, such as in sand.