Rear diffuser?

[freebeard]

Five fences is about right.

[aerohead]

Originally Posted by airbiteses

Hello, do these rear bumper extensions improve aerodynamics?
The factory bottom of the bumper looks like this:


and there are such replacements, i.e. additions to the bottom of the bumper:



Because there are tests on the Internet that reduce air resistance

1) You'd need to be extremely specific about what you actually mean by the use of the word.
2) We'd need a technical drawing with an accurate side elevation view, of a specific car, depicting the exact geometry, before and after, without and with.
3) The presence of a separation-caused, vortex-induced 'upwash' on a steeply-angled diffuser would be indicating for increased air resistance.
4 The diffuser on a Lucid Air would be a better 'benchmark' for a low drag diffuser.