HANG up the keys to the HSV and file away the memory of its thundering V8. The future of motoring sounds like someone vacuuming in the next room and looks like a windscreen on wheels.

This strange vehicle is General Motor's Hy-wire, a concept car that visited Sydney for the first time last week as part of an international tour.

It was a star of the Paris motor show two years ago and for GM, represents a huge step into the future. It's the first driveable hydrogen-powered car that uses drive-by-wire steering, throttle and brakes.

The global car giant believes hydrogen will be tomorrow's motoring fuel and it plans leadership of the market.

"We aim to become the first manufacturer to sell one million fuel cell vehicles profitably," said Steve Carlisle, vice-president Asia-Pacific planning at GM.

The Hy-wire's visit gave motor journalists a chance to get behind the "wheel" and local GM outpost Holden an opportunity to flag its research efforts. The company's R&D arm, Holden Innovation, is engaged in a joint research program into supercapacitors with the CSIRO.

Hydrogen cars either burn it directly in a modified petrol engine, or feed the hydrogen into a fuel cell stack, which then generates electricity to power motors that turn the wheels.

GM and Holden believe the second option will prove most feasible.

"Electric propulsion will be the basis of practically all vehicle powertrains in the long term," said Laurie Sparke, chief engineer of Holden Innovation.

"Supercapacitors are our particular interest. They're capable of providing a rapid surge of power and allow the super-fast collection, storage and discharge of the electrical energy necessary for automotive applications."

Sparke believes Holden-CSIRO supercapacitors will appear in future GM fuel cell cars -- although the Hy-wire itself doesn't use them.

Most hydrogen cars modify existing models, as GM has done with its fuel cell Zafira, called Hydrogen 3. By contrast, the Hy-wire started with a clean sheet of paper and looks very 21st century.

Instead of a conventional chassis, a 25cm thick skateboard-like platform houses the fuel cells, batteries and control systems. Propulsion is from a 94kW electric motor driving the front wheels.

The steel and fibreglass body sits on top, with information on driver inputs to steering, brakes and throttle transferred to the platform electronically via a universal docking connection.

Because there's no engine bay or transmission tunnel, the car has a flat floor from nose to tail, and the body is effectively one large box. The rear-hinged rear doors do away with a central body pillar and so the entire side of the car opens for access.

The seat cushions are mounted directly on the floor, Turkish restaurant style. From the driver's seat, there's the odd sensation of nothing in front except a floor-to-ceiling windscreen, divided at groin height by a sort of "modesty" bar.

There's no dashboard -- the aeroplane-like control pod is mounted on an extension of the centre console, and can be moved in front of left or right seats. The controls adjust to the seats, rather than the other way around.

Cameras relay rear views to TV screens ahead of the driver. In this car you can see and be seen.

The inside of Sydney's Hordern Pavilion must be one of the more unusual drive programs we've encountered, but it served to demonstrate one thing straight away: the lack of exhaust fumes.

Hydrogen fuel cells produce only water as a by-product, and tell-tale dribbles of H2O on the Hordern floor were the only pollution hazard from running the vehicle indoors.

There's motorcycle-like thinking to the controls. Turn the tiller to steer and accelerate by twisting the hand grips, which also have brake "levers" attached. Drive or park are selected from centre console buttons.

Two laps of the Hordern were never going to leave definitive impressions -- but they were enough to know the Hy-wire would take some getting used to.

It feels slow to respond to both steering and throttle, but grabby on the brakes.

Dynamically it's different too, with a wobbliness that its GM minders put down to the car's torsion bar axles and soft suspension set-up.

However, electric motors deliver strong torque from go to whoa, and despite weighing a hefty 1900kg the Hy-wire felt quick enough off the mark.

GM is expected to unveil the Hy-wire successor next year, possibly at the Detroit motor show in January.

Request to GM boffins: make it sound like a car.