Formula One Technology Explained - Diffusers

Diffusers

The new regulations for the rear diffuser (1000mm wide, 175mm high) announced the FIA’s intention to make Formula One more exciting. The changes minimise the effect of the dirty air that a car may have on the car behind, allowing the following car to follow more closely and increase overtaking.

Diffusers

Single Diffuser:The upswept area of rear floor draws air from below car. Generates 30-40% of total downforce.

Double decker diffuser: The vertical openings in floor of car (A) feed the ‘extra’ volume of second diffuser (B), increasing downforce

How Diffusers work:

The rear diffuser has two main aims. Firstly, the ‘Venturi Effect’ states that the speed of airflow is faster when the channel (the diffuser) it passes through is constricted. This lowers the air pressure, sucks the car to the ground and, in Formula One terms, creates downforce.

The second important benefit of the rear diffuser is to pull the air through from underneath the car. This fast flow of air reduces the layer of air molecules that sticks to the body of the car and as such increases downforce. As a result, the diffuser aids downforce along the entire length of the car, not just at the rear of the car.

Single vs Double Diffusers:

When designing the rear diffusers, the teams’ aim was to maximise the area in which the diffuser could have benefit. They did not want to simply create downforce in the area of the diffuser, but actually spread it over as large a plane area and as far forward as possible to maximise the benefits.

Using the regulated width and height, the double decker diffusers add a second storey to the diffuser structure. This not only increases the downforce in the diffuser area, but also starts to work further forward, stabilising the car more evenly.

The second deck of the diffuser is fed by holes in the floor of the car between the skid block and the reference plane. The regulations state that the floor of the car must have no holes or cut-outs that allow any part of the internal components of the car (sprung mass) to be seen from underneath, so the teams would have to be really careful when designing their double decker diffusers.

Why the double decker diffusers were declared ‘legal’?

BrawnGP’s defence in using their double decker diffuser relied upon the assumption that the skid block and the floor of the car should be considered individually, thereby arguing that the ‘holes’ in the floor were simply gaps in the connecting planes. Ferrari and the other appealing teams, however, took the two planes to be one single surface, rendering the holes illegal.

The FIA ruled that the double decker diffusers were legal, owing to their interpretation of the regulations that the two planes were individual and not one connecting surface. Technical innovation is central to the ethos of Formula One and this interpretation is simply an example of how the smallest of gains can make such a difference to the World Championship.