Banned: Why double diffusers were outlawed

The 2009 Formula 1 season will long be remembered as the year that Brawn GP emerged from the ashes of the Honda team and went on to win the world championship.

Banned: Why double diffusers were outlawed

But, the bottom nearly fell out of its challenge as soon as the season started, with a row erupting over a contentious design feature of its car: the infamous double diffuser.

We take a look back at why the concept that some teams got a head start on wasn't banned immediately, and how everyone reacted that season.

The wide sweeping rule changes introduced for 2009, with the intent of improving the ability of drivers to follow one another and thus improve overtaking, had sought to reduce the overall downforce that was achievable.

F1's designers were clearly in search of ways of reversing this and three teams, who don't at first seem remotely connected, universally struck upon the idea of adding a secondary tier to their diffuser.

It's an idea that was reportedly dreamt up by Super Aguri designers working on plans for the then 2008 rule change.

The team's demise would see its personnel go off in different directions, although most would find their way to Honda, who'd been bankrolling the exercise to a large extent anyway. Some landed with the other Japanese team on the grid – Toyota, or the Toyota-powered team Williams.

The double deck diffuser that could be seen on the BGP001, the Toyota TF109 and Williams FW31 was immediately put under scrutiny by the rest of the grid, who'd clearly missed an opportunity to expand the volume of their diffuser and sought to remove any advantage the three teams had gained.

Williams FW31 2009 double diffuser detail
Toyota TF109 2009 double diffuser detail

The rules introduced for 2009 had set about limiting the dimensions of the diffuser to 1000mm wide, 175mm tall and 350mm long.

The use of the double diffuser arrangement hinged on the wording on article 3.12.7 of F1's Technical Regulations.

It stated: "No bodywork which is visible from beneath the car and which lies between the rear wheel centre line and a point 350mm rearward of it may be more than 175mm above the reference plane. Any intersection of the surfaces in this area with a lateral or longitudinal vertical plane should form one continuous line which is visible from beneath the car."

The fact that this only required for the designers to be compliant in one dimension opened up the possibility for channels to be created, which allowed airflow to move into the upper deck of the diffuser.

Ferrari F60 (660) 2009 diffuser comparison with F2008
Ferrari F60 (660) 2009 diffuser comparison with F2008

This was an ingenious workaround that exposed the way in which the regulations had been written.

The design did not go down well with the other teams which, having missed the trick, knew it would be an issue to get a double diffuser incorporated on to their cars in the short term.

As such, they opted to protest the design at the Australian GP and lobby the FIA not only to ban the design going forward but also reverse the result of the Melbourne race.

Brawn BGP 001 2009 double diffuser detail view

Brawn BGP 001 2009 double diffuser detail view

Photo by: Giorgio Piola

Playing their hand in this way is just one way of winning though, as whilst in the public spotlight they appear to be doing the gentlemanly thing of having a borderline solution banned, they're also hiding a trump card up their sleeve: working on their own solution in case their political manoeuvres backfire.

In this case, the politics failed them, as they were unable to lobby for the double diffuser's removal. So now they'd have to fast track designs from the drawing board and get them on the car as quickly as possible.

The scale of this endeavour should not be underestimated, given how having more downforce on the rear-end would have to be matched at the front for aero balance purposes.

The benefits of the diffuser could not be ignored though, given how much downforce could be gained, and so everyone set about introducing their own version.

Red Bull RB5 2009 rear suspension detail

Red Bull RB5 2009 rear suspension detail

Photo by: Giorgio Piola

Red Bull had the biggest challenge, as it had reintroduced pull rod suspension at the rear of the car. This was a decision that has had an effect on the design of F1 cars ever since, with everyone seeing the packaging and aerodynamic advantages on offer.

It would, however, make life difficult for Adrian Newey and his team, as the pull rod joined the gearbox and crash structure assembly right on the diffuser kick line. This made it extremely difficult to get the best from a double diffuser.

Nothing is insurmountable though and Red Bull, knowing it needed this solution, set about making the necessary changes, irrespective of the upheaval it would have.

Red Bull RB5 2009 raised gearbox detail
Red Bull RB5 2009 raised gearbox detail
1/5

Photo by: Giorgio Piola

With the pull rod mounted in such a way, the team set about raising its gearbox in order to clear space for the double diffuser.
Red Bull RB5 2009 rear-end packaging
Red Bull RB5 2009 rear-end packaging
2/5

Photo by: Giorgio Piola

The channel for its double diffuser can be seen here nestled away under the gearbox.
Red Bull RB5 2009 diffuser underside view
Red Bull RB5 2009 diffuser underside view
3/5

Photo by: Giorgio Piola

In order to maximize the amount of flow into the upper deck of its double diffuser, Red Bull created a large throat either side of the lower floor section that carries the plank. This then tapered into a keel shape underbody, which merged with the crash structure to keep flow at maximum through the normal diffuser.
Red Bull RB5 2009 double diffuser detail
Red Bull RB5 2009 double diffuser detail
4/5

Photo by: Giorgio Piola

These developments were introduced in Monaco but continued to be paired with the long endplate design championed by Newey and his team since the start of the season.
Red Bull RB5 2009 diffuser detail comparison
Red Bull RB5 2009 diffuser detail comparison
5/5

Photo by: Giorgio Piola

The team would continue to bring developments for its diffuser design in the coming races and finally relented and moved toward a full-width design.

A challenge for everyone….

Red Bull might have had the biggest challenges to overcome to install a double diffuser but that's not to say the others had it easy either.

Toyota TF109 2009 double diffuser airflow detail
Toyota TF109 2009 double diffuser airflow detail
1/9

Photo by: Giorgio Piola

Toyota started the season with a double diffuser but, by the second round in Malaysia, the team had an even more advanced triple layer variant.
Ferrari F60 (660) 2009 rear view
Ferrari F60 (660) 2009 rear view
2/9

Photo by: Giorgio Piola

Ferrari's introductory diffuser design followed the intent of the dimensional regulations
Ferrari F60 (660) 2009 diffuser detail
Ferrari F60 (660) 2009 diffuser detail
3/9

Photo by: Giorgio Piola

Ferrari's double diffuser arrived a few races after the FIA had agreed they'd be allowed throughout 2009.
Ferrari F60 (660) 2009 diffuser underside view
Ferrari F60 (660) 2009 diffuser underside view
4/9

Photo by: Giorgio Piola

This view from the underside shows the effort made by Ferrari to use multiple entrance points, given it couldn't do so on the kickline due to packaging restrictions with its gearbox, suspension and crash structure.
McLaren MP4-24 2009 diffuser detail
McLaren MP4-24 2009 diffuser detail
5/9

Photo by: Giorgio Piola

The original McLaren diffuser for 2009 was more respectful of the original intent of the regulations. However, with the changes needed to accommodate a double diffuser not as dramatic for McLaren as others, it had a solution on the car just a week after the FIA threw out the team's appeal. The team had clearly been working on a solution in tandem with its protest, introducing the solution at the Chinese GP.
Renault R29 2009 diffuser development
Renault R29 2009 diffuser development
6/9

Photo by: Giorgio Piola

Renault was another team playing devil's advocate and arrived in China with a new arrangement that was given to Fernando Alonso. Nelson Piquet received the upgrade just a race later in Bahrain.
BMW Sauber F1.09 2009 double diffuser detail
BMW Sauber F1.09 2009 double diffuser detail
7/9

Photo by: Giorgio Piola

BMW Sauber was one of the last teams to introduce their double diffuser, with a new solution arriving for the Turkish GP.
Force India VJM02 2009 double diffuser development
Force India VJM02 2009 double diffuser development
8/9

Photo by: Giorgio Piola

Purchasing its gearbox from McLaren might have helped with the ease of packaging for Force India, which arrived with its own solution in Bahrain.
Brawn BGP 001 2009 Barcelona diffuser detail development
Brawn BGP 001 2009 Barcelona diffuser detail development
9/9

Photo by: Giorgio Piola

The BGP001 might have been considered to have the most refined double diffuser on the grid but that didn't stop the team from making further improvements. In Spain it altered the shape of the central section. The FIA continued to allow double diffusers to be used throughout the course of 2009 and 2010, given the resources expended by everyone to include them in their designs. But, from the start of 2011, the loophole that had allowed them to be installed in the first place was closed off in the regulations for good.
shares
comments
Pirelli plans to scrap F1 tyre choices once season starts

Previous article

Pirelli plans to scrap F1 tyre choices once season starts

Next article

"Detoxed" Alonso ready for F1 return, says Briatore

"Detoxed" Alonso ready for F1 return, says Briatore
Load comments
What Verstappen is risking with his current stance on 2021 F1 world title defeat Prime

What Verstappen is risking with his current stance on 2021 F1 world title defeat

OPINION: Max Verstappen is back in the lead of the 2021 Formula 1 drivers’ championship, with the season’s final flyaway events set to get underway in the USA this weekend. But a defensive stance he’s recently adopted could have a lasting impact for the Red Bull driver when it comes to his chances of defeating Lewis Hamilton and Mercedes

The hidden Ferrari struggle that Sainz’s recent charge put to rest Prime

The hidden Ferrari struggle that Sainz’s recent charge put to rest

Despite appearing to adjust to life as a Ferrari driver with relative ease, it was far from straightforward under the surface for Carlos Sainz. But, having made breakthroughs in rather different routes at the Russian and Turkish races, he’s now targeting even greater feats for the rest of the Formula 1 season

The final throes of Brazil's fleetingly successful F1 team Prime

The final throes of Brazil's fleetingly successful F1 team

Emerson Fittipaldi is better remembered for his Formula 1 world championships and Indianapolis 500 successes than for the spell running his eponymous F1 team. Despite a hugely talented roll call of staff, it was a period of internal strife, limited funding and few results - as remembered by Tim Wright.

Formula 1
Oct 18, 2021
Why McLaren's expanding agenda will benefit its F1 resurgence Prime

Why McLaren's expanding agenda will benefit its F1 resurgence

In the 1960s and 1970s, McLaren juggled works entries in F1, sportscars and the Indy 500 while building cars for F3 and F2. Now it’s returning to its roots, expanding into IndyCars and Extreme E while continuing its F1 renaissance. There’s talk of Formula E and WEC entries too. But is this all too much, too soon? Stuart Codling talks to the man in charge.

Formula 1
Oct 17, 2021
How Tsunoda plans to achieve his F1 potential Prime

How Tsunoda plans to achieve his F1 potential

Yuki Tsunoda arrived in grand prix racing amid a whirlwind of hype, which only increased after his first race impressed the biggest wigs in Formula 1. His road since has been rocky and crash-filled, and OLEG KARPOV asks why Red Bull maintains faith in a driver who admits he isn’t really that big a fan of F1?

Formula 1
Oct 15, 2021
The danger of reading too much into F1's clickbait radio messages Prime

The danger of reading too much into F1's clickbait radio messages

OPINION: After Lewis Hamilton responded to reports labelling him 'furious' with Mercedes following his heated exchanges over team radio during the Russian Grand Prix, it provided a snapshot on how Formula 1 broadcasting radio snippets can both illuminate and misrepresent the true situation

Formula 1
Oct 14, 2021
How F1’s pole winner approach undermines drivers Prime

How F1’s pole winner approach undermines drivers

OPINION: Valtteri Bottas is credited with pole position for the 2021 Turkish Grand Prix, despite being beaten in qualifying. This is another example of Formula 1 and the FIA scoring an own goal by forgetting what makes motorsport magic, with the Istanbul race winner also a victim of this in the championship’s recent history

Formula 1
Oct 13, 2021
Turkish Grand Prix driver ratings Prime

Turkish Grand Prix driver ratings

On a day that the number two Mercedes enjoyed a rare day in the sun, the Turkish Grand Prix produced several standout drives - not least from a driver who has hit a purple patch of late

Formula 1
Oct 11, 2021