Diffuser

The diffuser is the rearmost section of a Formula 1 car's floor, where the airflow from under the car is gradually expanded (diffused) before exiting at the rear. As the airflow expands, it slows down and its pressure increases, creating a pressure differential between the underfloor (low pressure) and the atmosphere (higher pressure) that generates downforce. The diffuser is one of the most important aerodynamic elements on a modern F1 car, generating a significant proportion of the total downforce. The shape, size, and complexity of the diffuser is tightly regulated. The "double diffuser" controversy of 2009 saw Brawn GP, Toyota, and Williams exploit a loophole in the regulations to create a more powerful diffuser, contributing to Brawn GP's championship victory.

The diffuser has been a key aerodynamic element since the ground effect era of the late 1970s. The 2009 "double diffuser" controversy was one of the most significant technical disputes in recent F1 history. The 2022 regulations significantly changed diffuser design as part of the ground effect reintroduction.