Diffuser Dispute

Brawn, Toyota and Williams have had their diffusers deemed legal by stewards in Australia throwing the ball back in the other teams' court. Protests will not be heard until after Malaysia which probably means that points will stand for the first two races even if they are later deemed illegal - how could the three teams run within the laws when they had already been told it was fine? So what's the problem?

The Diffuser
A diffuser is a shaped section of the car underbody which improves the car's aerodynamic properties by easing the transition between the high-velocity airflow underneath the car and the much slower airflow of the surrounding atmosphere. It simply works by providing a space for the airflow under the car to decelerate and expand so that the boundary is less turbulent. This increases the suction effect of the underneath of the car but also helps fill in the area behind the car. Otherwise, the gap in the air formed by the car is at a lower pressure and causes pressure drag.

The Diffuser Three

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Brawn

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Toyota

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Williams


The three teams at the centre of the row have produced fundamentally similar solutions although they appear different on the face of it. The difference can be best seen by comparing to one of the teams protesting against their interpretations, in this case Ferrari:



Ferrari and others have a simple diffuser with the upper surface at constant height as specified by the regulations. However, there is provision at the centre line of the vehicle to extend this area upwards and this is best seen in Toyota's diffuser. Larger volume equals a larger diffuser effect. In this, Toyota would seem to be safe. However, the teams have also opted to split the flow vertically with a second deck as shown in the Williams (shallow section below the rear light) and the Brawn (much deeper shaped section at the centre line). As the rules specify in terms of the bodywork that can be viewed when looking directly upwards at the bottom of the car, it is only in effect the lower of the two diffusers that have to fit within the prescribed dimensions. However, there is the question of how the airflow enters the upper diffuser. If from above the upper diffuser could in effect be interpreted as being a wing and that would be illegal. Alternatively the air could enter from below but such an opening that would be required in the bodywork would be deemed illegal. Air could enter from the sides but this is difficult to envision considering the location of the upper deck. Indeed, in the case of the Brawn it is possible to see through the upper diffuser and so the opening is quite clearly visible.

The Spirit of the Law
In the 2009 regulations the diffuser was made smaller in order to improve overtaking. One issue with these diffusers even of they are deemed legal is that they go against the spirit of that regulation and could undo a lot of the Overtaking Working Group's hardwork. It's certainly no surprise that none of the three teams were part of the OWG. Some may say that's clever engineering and that such innovation should be applauded, the OWG possibly also has a right to feel annoyed.

Quote:
"There’s no such thing as the spirit of the regulations, luckily!" - Adrian Newey's comments come back to bite him

If They're Illegal
The teams will have to remove them (Toyota for one flew to Australia with alternatives just in case) but that will not be until after Malaysia at the earliest. Any points collated in the first two races may be taken back, in which case the points may or may not be redistributed between the other competitors. However, in light of the FIA and the stewards declaring them legal it may be more likely that the teams would keep their points and the phrasing of the regulations clarified in order to ban them from further races.

If They're Legal
In this case there will be a rush to adopt the new diffuser designs. However, that may not be straightforward. Red Bull / Toro Rosso have a very low-slung rear and the pull-rod suspension that seemed so innovative a few weeks may suddenly start looking like a bad idea - they simply don't have the space for the modifications.

Other teams may also have to take a fundamental look at the front of the car at the same time. Look at the three cars in profile and you'll notice a fairly high nose, the aim being to increase airflow under the car in order to gain maximum benefit from the diffuser. Renault and Ferrari on the other hand have relatively low noses, BMW Sauber's nose is wide and flat, Red Bull's nose has raised sides - they've all gone for an approach of passing the air over the car to gain some downforce. Coincidence that these are the four teams leading the protests?

So how about McLaren who have kept quiet on the issue? That may simply to be to do with the fact that Mercedes are supplying engines to the Brawn but interestingly, McLaren may well already be on top of it if recent tests are anything to go by. As you can see from the picture, the McLaren diffuser has sprouted a curved section at the centre of the diffuser which looks similar to the Williams and Brawn designs. A cleverly blanked off section ready to go into action? It remains to be seen but the team would seem to have the least modification to do to adopt an increased diffuser, it may even be the case they are ready to run with it this weekend. Force India are also in a similar position with their very high nose. If the diffusers are deemed legal after Malaysia, we could be in for an interesting technological war in 2009.