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Double Diffuser Ban on Track for 2011

The Williams double diffuser

The Williams double diffuser

Brawn GP was clearly the class of the field at the beginning of tbe 2009 season.  Their speed was all the more surprising considering dismal performance of the 2008 Honda, which was the previous iteration of the car. Much credit was given to the so-called “double diffuser” for giving the Brawn package an extra edge.  Indeed, the three teams that began the year utilizing different versions of the double diffuser, i.e. Brawn, Williams and Toyota, all showed improvements compared to their 2008 levels of performance.

A double diffuser configuration adds perhaps 20% more downforce to a car, by directing airflow along the undertray of the chassis through an extra set of diffuser baffles at the rear end.  Engineers at the aforementioned teams independently took advantage of a perceived loophole (read: vague wording) in the new FIA technical regulations in effect for 2009 in the design of the diffusers.  Naturally, rival teams, who either (a) didn’t spot the loophole, or (b) decided not to interpret the grey area to their own advantage, cried foul.  Protests were filed, the FIA reviewed the matter, and the double diffusers were judged to be legal.

Naturally, at that point, the rival teams all scrambled to develop their own versions of the controversial device.  Adrian Newey, technical head at Red Bull, missed several races  to devote his full attention to redesigning the rear of the car.  He must have done a good job, as the Red Bull, on balance, outperformed the Brawn during the second half of the season.  However, the story doesn’t end there.

The purpose of the 2009 regulations, which greatly changed the aerodynamic profiles of the cars, was to reduce downfoce by 50%.  Reducing aero grip would, in turn, reduce a large portion of the turbulent or “dirty” that air trails behind a car in its slipstream.  When one car follows another into a corner, dirty air in the wake of the leading car robs the following car of its downforce, making overtaking nearly impossible.  Theoretically, reducing the dirty air would enhance overtaking opportunities, and improve the show.

Critics claimed that the double diffuser violated the spirit of the law if not the letter, by clawing back a significant portion of that sacrificed downforce.  Now, it appears that the 2009 regulations will be revisited, with an eye to eliminating double diffusers altogether.  According to a report in Autosport, FOTA’s Technical Regulations Working Group (TRWG) met late last year, and reached an agreement that double diffusers should be outlawed by 2011.

This decision was at least in some measure influenced by an estimate that in 2010 Formula 1 cars would receover all of the downforce they’d lost in 2009, even without the benefit of all the exotic winglets and Dumbo ears they’d sprouted during the previous one or two seasons.

Specifically, the TRWG is proposing that car undertrays should be flat along a longitudinal plane, which would eliminate the slots or ducts that direct airflow into the secondary diffuser baffles which generate the extra downforce.  The members of the TWRG have suggested that eliminating double diffusers will slow cars by, on average, a second per lap.

Ultimately, the TWRG will submit their recommendations to the FIA’s Technical Working Group (TWG).  If approved, the changes must be formally ratified by the FIA.

Mike Gascoyne, the new chief technical officer at Lotus, said of the proposed change, “I think it is exactly right.  It is what we should do, and it is what both FOTA and the FIA are looking at for 2011. I think it is very sensible and very easy to do – just tighten up the regulations and it is done.”

Ironcially, when asked if he thought that double diffusers had had a negative effect on overtaking in 2009, he said, “I don’t think there was a reduction in overtaking, but the changes to improve overtaking didn’t help. And in fact, if you look at the numbers, it was never going to.”

To add confusion to the matter, Gascoyne added, “But if you look at it carefully, what the aero group set out to achieve it actually did, and if you take the diffuser away it will do exactly what it said on the tin. Unfortunately that will never help you overtake anyone.”

So apparently, the aero changes mandated for 2009 were a failure from the start, with respect to overtaking, with or without the double diffusers.  Moreover, if it’s generally understood that the elimination of double diffusers would do little to improve overtaking, one wonders what purpose it would serve at this point.  Changing diffuser specs would necessitate, for many teams, a comprehensive redesign of the rear end of the car, including the suspension and gearbox.  This would seem to be another case of the FIA’s mandating questionable and expensive design changes in an era when they’re ostensibly championing reduced budgets.

Image by Depista, licensed through Creative Commons.

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