Mat Coch writes:

Having initially provided its thumbs-up to the new 2013 Williams, the FIA has back-peddled over the car's exhaust layout and declared the design illegal before the F1 season has even begun.

Unveiled yesterday the Williams FW35 features a Coanda exhaust, as has become the norm among Formula One teams. The Coanda effect relies on a carefully designed side pod, coupled with an equally carefully designed exhaust, which together provide an aerodynamic effect by bending the airflow down on to the floor of the car, near the rear wheels, thereby providing greater downforce.

It's a similar effect to that teams employed in 2011 with exhaust blown diffusers, and something which the sport's governing body moved to outlaw with strict new regulations introduced ahead of the 2012 season which dictated how and where the exhaust can exit the car's bodywork.

In Jerez Caterham raised eyebrows after its car sported a deflector in the channel where exhaust gases flow. It prompted Lotus Technical Director James Allison to suggest the exhaust may be revised ahead of the Australian Grand Prix.

The Williams exhaust came under similar scrutiny with a small piece of bodywork straddling the top of the exhaust groove. Initially it was understood the configuration had been approved for use by the FIA, however the governing body has now declared the design a contravention of the technical regulations.

While running the feature in testing is not a problem the team could come a cropper should it continue to run the design heading into the season proper. As a result it is expected the FW35 will feature a revised exhaust at the final pre-season test, also in Barcelona, beginning on 28 February.

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