Fitment Guide: 86/BRZ, 12-16
Diffusers work in conjunction with other aerodynamic components of a car to help produce downforce. Because a car displaces air as it moves forward, the air molecules in the rear of the car get disrupted causing a vacuum of low-pressure air.
To help channel the high-speed air flow coming from underneath the car, diffusers redirect the high-speed air flow to transition smoothly transition into the low-pressure vacuum in the rear. This encourages a smoother flowing air flow underneath the car and allows better performance from other aerodynamic components such as aerodynamic wings.