• Rule changes

Blown diffuser ban from British GP

Blown diffusers have been the focus of major investment for the teams © Sutton Images

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The FIA has told the teams that the practice of using exhaust gases to blow diffusers off-throttle will be banned from the British Grand Prix onwards.

Initially the FIA wanted to ban teams using exhaust gases off-throttle from the Spanish Grand Prix last month, but agreed to delay enforcing the ban after the teams highlighted cost and logistical problems. However, it wrote to teams on Saturday morning to inform them that it will implement the ban from next month's race at Silverstone, and apply even more strict restrictions in 2012.

The ban will apply to two types of diffuser blowing: 'hot blowing' and 'cold blowing'. 'Hot blowing' occurs when fuel is still forced through the engine off-throttle in order to ignite and then increase energy in the exhaust, with complex engine mapping stopping the engine from sending further drive to the wheels. 'Cold blowing' occurs when the throttle stays open while the fuel valves are closed, so no fuel is ignited and only cold gases are forced out of the exhausts.

The effect of both types is an increase in downforce at the rear of the car, with 'hot blowing' the more effective method. While all of the teams currently blow the diffuser, Sauber, Toro Rosso, Williams, Virgin and HRT only practice 'cold blowing', meaning that it is the leading teams that will feel the biggest impact. As of 2012, however, the FIA want to outlaw all blown diffusers and move the exhaust exits to the very rear of the car, preventing gases from having any effect on downforce.

The reason for the ban is the FIA is unhappy that 'hot blowing' is a waste of fuel, and believe that blown diffusers in general are making use of moving parts of the engine to influence aerodynamics, and therefore infringe a regulation against moveable aerodynamic devices. Williams technical director Sam Michael told Autosport that the Technical Working Group would be meeting on Thursday in order to agree on how it will implement the FIA's rules.

"The FIA has made its position very clear," Michael said. "They want to talk about the fine details on Thursday, but what Charlie [Whiting, FIA technical delegate] is saying is that hot blowing is banned and cold blowing is banned from the Silverstone GP onwards. For 2012, the exhaust system must exit behind the rear wheel centre line, actually 330mm behind, so right out the back of the diffuser.

"That means there cannot be any exhaust influence on the diffuser. That is what the FIA has clarified and then Thursday is about implementation."

Mercedes team principal Ross Brawn told the BBC that it would be difficult for the teams to prevent the ban coming in to force, and that the biggest difference would be noticed in qualifying.

"Unless the teams can show a definite major problem with the approach that means it's not feasible, it will go ahead," Brawn said. "In qualifying, it means a lap-time deficit of half to one second, although our race modes aren't going to be that different."

Brazilian newspaper O Estado de S.Paulo quoted Red Bull technical boss Adrian Newey as admitting he is angry.

"I agree with rule changes in the middle of a championship for good reason, like safety," he said. "But this is not the case. It's absurd."

FIA president Jean Todt said last week he is resolute because sophisticated 'hot' exhaust blowing is a "needless waste of fuel".

Renault boss Eric Boullier said: "We designed our car for this principle and already last year it was being used by some teams. We passed the technical inspection at the beginning of the championship. To give it up now would probably compromise our ability to achieve good results this year."

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