Turbulence - Friend or Foe? |Here's a lot of Aero info, not spread in several threads

[dosco]

Originally Posted by sonyhome

Diffuser:

In one of the links, it mentions for diffusers the use of a hollow space under the rear of the car to allow airflow to expand and slow down before exiting the underbody, to avoid further turbulences in the wake. If anything then the holes behind the rear bumper should not ne covered up. Maybe poke holes in the bumper at best. Maybe just put vertical separators to direct the flow and reduce turbulences in that gap?

I wouldn't spend too much time worrying about it. A diffuser is mostly applicable to race cars for generating downforce. They were developed to recover underbody-generated downforce that was lost when cars moved from "airfoil tunnel" to "flat-bottom" underbodies.

For a normally used road car, just putting something on the bottom of the car to "clean it up" will help reduce drag, thereby benifitting FE.