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Holden Adventra features Cross Trac - the first crossover all wheel drive system designed, calibrated and manufactured in Australia for unique local road conditions.
Holden has unveiled Cross Trac, the all wheel drive system powering Holden's ground- breaking new range of crossover vehicles.
Holden made a $125 million, four-year investment in Cross Trac. It will be the first crossover all wheel drive system designed, calibrated and manufactured in Australia expressly for unique local road conditions.
Cross Trac is a traction control-based, full time all wheel drive system which can be used in a wide range of passenger and light commercial applications. The system debuts next month when the Holden Adventra crossover wagon is released, followed by the all wheel drive version of the Crewman crew cab later this year.
Cross Trac forms a crucial part of Holden's business strategy for a series of next generation niche crossover vehicles catering for changing consumer needs and sales opportunities.
Holden formed a 20-strong specialist engineering team for the program and charged it with the task of developing a full time all wheel drive system that met a challenging set of criteria.
Grant Jamieson, Adventra Program Engineering Manager, said his team relished the job, which entailed a great deal of hands-on field testing as Cross Trac performance was continuously benchmarked against these criteria and against the performance of imported all roaders.
"More than 600,000 durability, development and test kilometres and 1000 complex computer simulations were used to ensure Cross Trac exceeded our key benchmarks for the Adventra program. From the outset, we knew the Adventra had to be well able to take most Australian road and dirt track conditions in its stride.
"This vehicle is not intended to be a rock hopper - but with its V8 power, good ground clearance and the high level of traction afforded by Cross Trac, it will handle a wide range of challenges," he said.
Holden's Cross Trac uses unique calibrations of Automatic Brake Differential (ABD) software and Electronic Brake Force Distribution (EBD) to achieve its desired levels of traction across all wheels.
Essentially, ABD detects excessive wheel spin at any wheel and controls it by redistributing drivetrain torque to the other wheels with more traction, allowing smooth acceleration without loss of grip. This adaptive torque transfer also aids acceleration on split surfaces. If two wheels are on bitumen and the other two are on an icy surface, for instance, the system applies differing amounts of brake pressure to keep all four wheels at their respective limits of adhesion.
EBD works in conjunction with ABS, distributing brake torque between front and rear axles to ensure maximum brake system efficiency and help maintain vehicle stability under all load conditions and on all surfaces. EBD also assists braking control when cornering by distributing brake torque across axles.
"On the highway and around town, however, the expectation was that it should perform and handle in a similar way to its rear wheel drive relatives, which it certainly does. For maximum flexibility and stability, Cross Trac has three open differentials and a torque split of 38 to 62 per cent front to rear, which gives us those characteristic Holden driving dynamics," Mr Jamieson continued.
"The ingenuity of the Cross Trac system is in the detail, particularly in the way it has been calibrated to cope with the deformable road surfaces, such as sand, gravel and loose dirt, that are typically encountered in Australia. 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, icy surfaces.
"There's no short cut to determining the best settings for our road surfaces. While we took full advantage of computer simulation technology, it's no substitute for taking the cars to the country and testing them, over and over again, in the real world.
"This depth of local knowledge has allowed us to program Cross Trac to use the torque available in the most efficient and effective way. It's crucial to the success of this system in most conditions over systems that don't enjoy the same advantage," Mr Jamieson said.
Holden engineers also placed a great deal of emphasis on calibrating slip targets, which factor in a range of variations, including surface friction, current vehicle velocity and gradient. Correctly calculated, they are vital to maximising vehicle performance on highly deformable surfaces as sand and gravel, which require relatively high rates of slippage to be handled successfully.
Cross Trac software is based on a system developed for the General Motors HUMMER 2 program and has been modulated for optimum use in Australia. The central controller has twin INTEL 16-bit microcontrollers, with 56 kilobytes of ROM and 16MHz processor speed.
There are 1781 calibration variables, which determine control strategies for all driving situations. More than 300 parameters were modified from the original software to cater for the hundreds of common driving scenarios inherent in Australian conditions. This in turn means that there are hundreds of thousands of possible situations in which Cross Trac will determine the optimum amount of torque split and wheel slip required to handle the job effectively - whether on an icy highway in the alps, a sandy road or gravel mountain track.
Full information on Holden's all wheel drive Adventra crossover will be released on 22 September and it goes on sale from 17 October.
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