Red Bull strength curbed as FIA bans use of Exhaust blown diffuser after Valencia

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The European Grand Prix at Valencia will be the last before the FIA clamps down on the use of ‘exhaust blown diffusers'. The technology, which continues to blow gases through the exhaust pipe even if the throttle is closed, is thought to have most benefited the Red Bull and Renault teams so far this season.

As has happened so often in Formula One, the teams cleverly exploited a gap in the regulations to boost their cars' performance. Back in 2009, teams began to use the blast of exhaust gases to the rear diffuser to generate more downforce and hence cornering grip.

However they had a problem. As the drivers closed the throttle the exhaust flow reduced and the back of the car became unstable just when drivers needed the grip most.

Engineers quickly found a solution to the problem. Instead of closing the throttle to cut off the power, they instead retarded the ignition timing when the driver backed off the accelerator. As the pressures inside the engine remained high, so did the blast of the exhaust onto the diffuser.

Then at the beginning of this season, we began to hear a new, distinctive rasp from car exhausts as they braked for corners. Renault, who also supply engines to Red Bull, had taken the concept even further by continuing to spray fuel into the red-hot exhausts on the over-run.

As the fuel burned and expanded, this ‘afterburner' boosted still further the airflow onto the diffuser. However the use of the technology provoked a clamp-down from the FIA.

"An exhaust system is there for the purpose of exhausting gasses from the engine and when you're off-throttle, it isn't doing that any more" explains FIA Technical Delegate Charlie Whiting. He believes therefore, that the exhaust is being used to influence the aerodynamic characteristics of the car, which infringes the technical regulations regarding the use of driver controlled aerodynamics.

From the race after Valencia, the British Grand Prix, teams will be limited to just 10% of the airflow in the cars' exhausts when the driver lifts off the accelerator. From 2012, the FIA plans to outlaw all use of blown diffusers, demanding that exhausts will exit upwards through the bodywork, well away from any aerodynamic aid.

It perhaps puts a little more pressure on Sebastian Vettel to repeat his 2010 performance at the Valencia street circuit. Last year he put the Red Bull firmly on pole position then cruised to a comfortable victory ahead of the McLarens of Hamilton and Button.

The omens look strong for a similar performance from Vettel this year, although team mate Mark Webber will not be keen to repeat his ‘Red Bull Air Race' aerobatics after clobbering Heikki Kovalainen's Lotus!

McLaren's pace in Montreal raises the question though, even if Vettel's Red Bull diffuser is going to give him one last blast, will it be enough to give him the championship? For a precedent, look back to 2009, when Brawn GP's development of the ‘double diffuser' gave Button six wins from the first seven races before the other teams could match their technology.

When his rivals caught up, after the Turkish GP at the start of June, the Briton never won again that year. However Vettel, Webber, Hamilton, Barrichello and Raikkonen all scored wins. Splitting the points total between them allowed Button to clinch the title in Brazil with a race remaining.

Ironically if the Red Bull's performance does dip Vettel might hope that not just McLaren, but Ferrari might start winning, to split the points from the second half of the season. Alternatively he could just prove us all wrong, by continuing his early season winning streak right through the year!