During the course of this series of articles detailing different aspects of Formula 1 car design, I have banged on about how important it is to get good quality airflow to the leading edge of the underfloor. And also how the vortex structure induced by the front wing then helps the performance of the underfloor by acting as a skirt to reduce the amount of air spilt under the sides of the floor.
The underfloor is responsible for around 35 per cent of the total downforce produced by the car and the only way that it can do this is by the diffuser accelerating the airflow under the large flat area of underfloor - creating a low pressure over this area.
The size and shape of the diffuser is very well controlled by the regulations and because of this it can only ever do a certain amount of work to that airflow.
If the flow at the leading edge of the sidepods is poor, or there is a lot of spillage under the sides of the floor, then the underfloor will not produce as much downforce as it does when the airflow is of high quality.