The 2009 Formula 1 season was a fairytale for Brawn GP, having recovered from its demise as the Honda squad from 2008 when the Japanese manufacturer closed its’ doors. Nothing could prepare the grid for what happened next.
The Super Aguri team had collapsed in 2008, with the majority of staff then joining Brawn, but some made their way to Japanese giant Toyota F1, and the Toyota powered Williams team. It was no coincidence when these three teams turned up to the first race of the 2009 championship in Australia with the famed double diffuser, to the uproar of the other teams down pit lane.
The reason Super Aguri is important here is that the double diffuser idea was born with the team before their own collapse. But more on that later.
The 2009 regulations were introduced to reduce downforce and increase the chance of overtaking. Part of the regs was a smaller diffuser in a more rearward position. With an estimated 50% reduction in downforce the teams looked for loopholes to regain the lost downforce.
The new regulations limited the main part of the diffuser to a width of 1000mm, a length of 350mm and a height of 175mm. The Brawn, Williams and Toyota diffusers exploited a loophole in the rules. The rear diffuser regulations are referred to as a section of the wider bodywork regulations. These include sections which allow bodywork in areas not intended for the diffuser. Where this gets critical is the fact that all three designs use a ‘window’ or opening to feed air to the top side of the diffuser. That opening is different for each of the three teams. Williams featured a horizontal opening, while Brawn and Toyota featured vertical opening. All are located where the flat floor meets the diffuser. The Brawn and Williams cars used ‘double deck’ diffusers while the Toyota used a more complicated ‘triple deck’ design.
The teams exploited the central crash structure at the rear of the car. Where the literal interpretation of the rules suggests a 1000mm wide channel the same height all the way across, Brawn, Williams and Toyota split that into 3 channels using the crash structure as a central channel. Toyota’s diffuser exploited regulations that allow extra bodywork within a 150mm zone in the center of the car. The team shaped the TF109s rear crash structure so that it lengthened and heightened the diffuser’s central section.
There was a questionable rule which appeared to allow more than one surface to exist in this area. The three teams were able to create a double decker diffuser, their main diffuser is as long, wide and tall as the rules permitted, but they then made their middle sections stop short of meeting the flat floor section. The floor instead extends into the upper diffuser creating an opening to allow airflow above the main diffuser which itself creates more diffuser exit area. And hence the greater flow expansion through the diffuser creates more downforce.
The Super Aguri Link
Finally, Formula 1 journo Will Buxton has said of the Honda/Brawn/Super Aguri tie up
The BGP001, which would have been the Honda RA109, benefitted greatly from 18 months of design work undertaken at Leafiled by the Super Aguri F1 Team which had begun in 2007, a year of design work at Honda in Brackley and Tochigi during 2008, and, it is understood, additional work at the Dome base in Maibara, Japan. The double decker diffuser concept, which would prove so pivotal to the success of the BGP001, is believed to have come from either Super Aguri or Dome. At times it has been claimed that anywhere between four and six wind tunnels were in operation, through the various different arms of the development chain, at one time.