McLaren-Mercedes is confident of being able to upset the balance of power and gain as much as 'half-a-second' in lap time in qualifying on runaway F1 2011 World Championship pace-setters Red Bull Racing once the ban on blown exhausts comes into force from next month's British Grand Prix.

Following a meeting of the FIA's Technical Working Group in London yesterday (Thursday), it was decreed that the clampdown on off-throttle blown diffusers - as outlined in a letter sent out by the sport's governing body to teams over the weekend of the Canadian Grand Prix in Montreal [see separate story - click here] - would be going ahead as planned from Silverstone onwards, despite opposition from a number of entrants, Red Bull and Renault chief amongst them.

The 'extreme' practice of using engine mapping to operate blown diffusers - thereby sending a full blast of exhaust gases into the diffuser when the driver is off the throttle in corners - has been outlawed, the FIA states, to avoid altering 'the aerodynamic characteristics of a car beyond the primary purpose of generating engine torque' and in the interests of conserving 'financial, technical and human resources' in an era of strict belt-tightening. All blown diffusers will be illegal from next season.

The off-throttle blown diffuser is believed to be a key element behind Red Bull's competitiveness in 2011 - particularly in qualifying, with Jenson Button telling Blick that 'they use the exhaust gases into the diffuser non-stop on a qualifying lap, but not in the race'. Moreover, a Pirelli source has told Brazilian newspaper O Estado de S.Paulo that the energy drinks-backed outfit's exhausts 'are too close to the tyres', with a recommended distance on safety grounds of at least 40cm due to the heat generated.

"This is about an interpretation of the rules," remarked Force India F1 chief operating officer Otmar Szafnauer, according to "If the interpretation is different to the FIA, the teams can appeal, but on the other hand, the court's ruling will be the interpretation of the federation."

McLaren team principal Martin Whitmarsh, meanwhile, hopes the change might just enable the Woking-based outfit to finally get on terms with RBR in qualifying this season, with the MP4-26 having proven to be much more of a match for the RB7 in the races, but invariably losing out through conceding too much ground on Saturday afternoons.

"It's quite possible we will close up in qualifying by half-a-second," the Englishman mused, speaking to Auto Motor und Sport, before adding rather more cautiously to "I don't think it will create a fundamental change to the picture, but it will hurt some more than others. Depending on how optimistic you are feeling that day, you like to think that it will hurt others more than you.

"It will change according to which team is exploiting these tactics the most. It's been a moving feast. You can hear changes and difference in some teams [in exhaust note] which will not be there when we get to Silverstone."