Spectators at the Repco Rally Australia round of the World Rally Championship next September will see physics-defying action from cars that look similar to models seen every day on the roads but are exotically different under the skin.

The Subaru Impreza WRC, Ford Focus, Citroen C4 and Mitsubishi Lancer Evolution that vie for every WRC round are based on popular small cars available in Australia at prices starting below $40,000.

But their cost may be as much as $1 million by the time they reach the start of their first competitive special stage.

Thousands of hours of computer-aided design, meticulous construction and on-road testing turns them into pocket-rockets capable of accelerating as fast as a Ferrari while even in their highly-developed state remaining fully road-legal.

Rally-driven development over several models of the Subaru and Mitsubishi have seen them become icons of the performance road car and computer game scenes, although it is the Citroen and Ford now setting the pace on rally special stages around the world.

WRC cars heading to northern New South Wales for round 10 of the 12-round series on 3-6 September are based on 2.0-litre, four-cylinder production models, but as competition machines just about everything about them is different, according to the official website WRC.com.

Under relatively mundane bodywork, they are as technically sophisticated as any car in motorsport, employing aerodynamics, lightweight materials, engine turbocharging, sequential-change gearboxes, electronically-controlled all-wheel drive systems and advanced engineering techniques, among other things, to achieve high levels of performance, reliability and safety.

Many rally car developments contribute to greater efficiency and safety in their roadgoing stablemates, at a time when these things are the mantra of manufacturers around the world.

The creation of a World Rally Car begins with a standard production bodyshell, as stipulated by world motorsport governing body FIA.

It is stripped to bare metal and completely rebuilt. Unnecessary brackets and mounting plates are removed to save weight and a tubular steel roll cage is welded in for safety and strength.

After around 700 hours of work, the body emerges vastly stronger and stiffer – most WRC cars could support the weight of 10 road cars.

The engine block and cylinder heads also must be production-based, although internal components can be modified.

Exhaust gas-driven turbochargers pressurise the engine at up to five times the rate of a standard turbo road car. The result is that while power output is limited to around 223 kiloWatts through the regulated use of an intake restriction device, torque (pulling power) is a massive 600 Newtonmetres – much more than a 5.0 litre Australian V8 Supercar and about the same as a V12 Ferrari Enzo.

Maximum turbo boost from idling revs, all-wheel drive with electronic launch control systems and six-speed semi-automatic transmissions able to make clutch-less gearchanges as fast as a Formula 1 car combine to launch a World Rally Car off the start-line like it has been fired from a catapult.

With a typical rally special stage comprising more bends, climbs and descents than straights, acceleration is everything in a rally car and top speeds are low compared to circuit-racing vehicles.

World Rally Cars are designed to allow team members the easiest possible access to mechanical parts during service breaks in the event timetable.

Besides interrogating data from the on-board electronics systems, refuelling, changing tyres and making running adjustments, a team of four technicians is allowed to perform mechanical work on their car during the strictly-limited stops of 10 minutes 30 minutes or 45 minutes.

Being able to work in this pressured environment means WRC technicians are some of the best in the world, capable of extraordinary ingenuity, speed and occasional miracles.

In the heat of competition, a suspension upright, wheel hub and brake unit will be swapped in around five minutes and a gearbox in 10 minutes, while the technicians’ skills with hammers, welders and adhesive “race tape” have regularly turned a sorry-looking wreck into a rally winner.

Inside a WRC car there is no fancy upholstery or elaborate trim – just painted metal, composite panels and two carbon fibre seats tailored to the driver and co-driver (navigator).

There is no room in the back, which is criss-crossed with the roll cage tubes. As many components as possible, including the co-driver’s seat, are located to achieve the lowest centre of gravity and optimum distribution of weight between the wheels.

The fuel tank is designed to be virtually burst-proof and spill-roof, using aircraft-type bladder inside a rigid case, with automatic cut-off valves and dry-break refuelling connections.

Mechanical and road noise inside the cabin are high, so driver and co-driver communicate via two-way radio built in to their lightweight helmets.

Rally rules allow spoilers and other aerodynamic aids not seen on road cars. These are designed to manage airflow around the car to cool mechanical components, including engine and brakes, and to keep the car firmly planted planted on the road.

The result of the long, intense building process is a World Rally Car that will accelerate from rest to 100 kmh in three seconds on any surface, withstand massive punishment and, in action on the Repco Rally Australia special stages, provide spectators with an unforgettable experience.
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