Edge in wheel arch

[MartijnV]

I've looked at some images of the M3 GT2. And there I saw a standing edge inside the wheel arch.
What is this for?

[wesley123]

the vertical gurney creates low pressure causing air to escape the wheel arch, increasing downforce. Vents and cutouts in this area do the same thing.

[PNSD]

Yup, just one method of helping the flow through the front diffuser.

[machin]

It also increases pressure on the outer edges of the splitter (i.e. just infront of these flat plates) -increasing the downforce coming from those areas.