The Double Diffuser: One of the Greatest F1 innovations

Breaking the rules.... while following them

1y ago
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In this series of articles, I will write about some of the greatest F1 innovations and the cars that carried them. Some were good, some were bad and some were so abysmal that no one remembers them. In the first article of this series, I talked about the fan car and you can read that post here:

A little bit of background

In 2009, the regulations were massively different to 2009. Many designers from the 1990s and 2000s believe that this was the biggest regulation shake-up ever, even more than the 1998 rule changes. Basically, the FIA realised that all the aero appendages that had sprouted on the car during the early noughties were producing a lot of dirty air, which was preventing many overtakes. Just to put it into perspective, the 2008 cars produced more dirty air than the current breed of F1 cars. Just as with the new 2022 regulations, the aim of the 2009 regulations was to decrease aero and promote overtaking by closing up the field. The rules were supposed to be implemented in 2008, but a few teams, including Red Bull, requested the rule change to be postponed by one year, stating that it would allow all teams to produce a good car.

This image clearly shows the difference that the new regulations made

This image clearly shows the difference that the new regulations made

So, how did the double diffuser happen?

The regulations stated that the step plane(the bit of the floor that the plank is attached to) and the reference plane(the actual floor) must be flat an uninterrupted, meaning that they shouldn't have any holes in them. However, a Japanese engineer at Honda realised that the regulations did not say anything about the transition from the step plane to the reference plane. By putting a hole in this area, teams were able to essentially raise the diffuser height. The regulations stated that the diffuser could only be 175 mm high, but with the double diffuser, teams could raise diffuser height to around 300mm, which would give the double diffuser teams a huge amount of downforce compared to the non double diffuser teams. It is believed that Honda were the first team to discover this loophole, but Williams may have discovered it at the same time. However, after Honda pulled out of the sport at the end of 2008, a large part of Honda's staff was made redundant. Many of these peole joined Toyota and so, Toyota had enough information to incorporate the double diffuser into their car.

The workings of the Double Diffuser. Air flows through the hole in the transition and exits above the diffuser (Entry and exit highlighted in yellow and flow of air shown with arrows)

The workings of the Double Diffuser. Air flows through the hole in the transition and exits above the diffuser (Entry and exit highlighted in yellow and flow of air shown with arrows)

What happened then?

As it turned out, the F1 overlords Mclaren and Ferrari had no idea that there was such loophole, so their cars were painfully slow. Toyota were the fastest team around, which showed the potential of the double diffuser(remember that Brawn GP didn't join until the final pre-season test). Williams were, however, nowhere to be seen because they had put all their eggs in the double diffuser basket and that meant that their car was lacking in many other areas. This was most visible by the fact that Williams used the same specification Toyota engines as the works team. We all know the story of Brawn GP, the team who rose from the ashes of the Honda team and turned up to the final test with a rocketship. Brawn GP was the most famous and successful of all the double diffuser cars of 2009, so their initial pace was no fluke. Suffice to say, all the other teams raised a huge fuss about this, stating that this diffuser was against the spirit of the rules. It went so far that this issue was taken to the motorsport court in Switzerland, where the Ferrari team representative first called Ross Brawn an "arrogant" and egoistic man, and then accused the FIA of not understanding the issue! This issue was thrust into the limelight by the fact that Brawn GP won 6 out of the first 7 races and also took 10 podiums from the first 7 races. Teams later adapted the double diffuser to their cars and Red Bull and McLaren were able to take race wins and podiums as well.

Williams and Toyota were not as successful with the double diffuser as Brawn GP

What was the difference between the single and double diffusers?

As already mentioned, the double diffuser raised the height of the diffuser by 125 mm. This may not seem like much, but it increased downforce by a huge amount. However, it wasn't easy to integrate into the car. Apparently, in order to fit the double diffuser to a car, it needed a new floor, a new engine cover, gearbox casing (so a new gearbox as well) and a new diffuser. Adrian Newey tells us in his autobiography that the Red Bull team tried getting the double diffuser quickly, but it ended up making the performance worse and not better.

Looking at the diffusers side-by-side, you can clearly see the complexity of the double diffusers

Looking at the diffusers side-by-side, you can clearly see the complexity of the double diffusers

So, how long did the double diffuser last?

The double diffuser lasted one more year, when everyone had managed to integrate it into their cars, except the new 'backmarker' teams of Lotus, Hispania and Virgin. Although everyone realised the potential of the double diffuser, none so than the great Adrain Newey. By coupling this diffuser with a blown diffuser, Red Bull were able to produce more downforce than ever before. Many people- including Adrian Newey- still believe that this was the casr that produced more downforce than any other F1 car. ever. However, as cars got faster, the FIA decided to ban the double diffuser, along with other aerodynamic devices, which was supposed to slow down the cars.

The RB6 coupled a double diffuser with a blown diffuser and the results were amazing

The RB6 coupled a double diffuser with a blown diffuser and the results were amazing

Thank you for reading this article. Bump if you enjoyed it and comment if I got anything wrong. Also, I want to continue this series, so please leave ideas of other great F1 innovations in the comments.

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Comments (4)

  • Sure it's very clever to design that dubbel diffuser, but it is also a cheeky one. because of the big advantages they had to the other cars (brawn gp). The other teams try to copy it, but trick didn't work for them during the season.

      1 year ago
  • And,that year, the (not mandatory) Kinetic Energy Recovery System. Great piece,though,thanks

      1 year ago
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