WRC explained: Aerodynamics

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"The cooling package is quite complex. But by putting the intercooler at the top and the other radiators at the bottom we try to keep the weight down and the centre of gravity as low as possible."

Once the air has passed through the cooling system it is expelled, by electric fans, from two rectangular exhaust ducts on the top of the bonnet. "We fully duct the system so the airflow doesn't go into the engine bay. By doing this we also get some benefits in terms of downforce and reduced drag," explains Loriaux.

Unlike its road going counterpart, much of the front grill above the bumper is blanked off on the Focus World Rally Car, with the area to the right of the Ford badge used purely to direct air into the engine intake. "We try to use the ram-air effect here, to use the speed of the car to pressure the air in the airbox. Getting as much pressure into the airbox means more power," says Loriaux.

Reducing drag

The amount of drag, or air resistance, created by a World Rally Car depends upon its surface area, which in turn is defined by its size. As WRC regulations limit bodywork modifications it is difficult to dramatically alter the drag characteristics of a rally car. In other words, you're pretty much stuck with the same characteristics of the road car.

"But what we can do is try and trim it to make it as efficient as possible going through the air," says Loriaux. "For instance ducting out the cooling package allows us to reduce the drag, meaning a higher top speed and lower fuel consumption."

The roof scoop on the rally car obviously has drag implications, but Loriaux insists it compares favourably to alternatives like ducted fans. "The fact is we find it quite efficient. We get fresh air, without any dust, and it works well to cool the drivers," he says.

Downforce

Downforce is downward pressure, created by the aerodynamic characteristics of a car, which presses it onto the road and increases grip. It is created by reversing the same principle that allows an aeroplane to take off by creating lift under its wings.

Downforce in the WRC was at its peak in the Group B era of the early 1980s, when cars like the Peugeot 205 T16 and Audi Sport Quattro S1 each sported an assortment of spoilers, splitters and huge wings designed to stick them to the ground. But when Group B cars were outlawed in the mid 1980s, most of the downforce devices were banned too.

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