For the experts out there on diffusers...

[Mike]

shows the rear diffuser works

E-Slap....

 

[harleybarley]

it does do something, ive heard its around 40kg of downforce at motorway speeds.

this is only what ive heard, cant be arsed to research it tbh

 

[Paul]

I would say that it works to a degree, obv not going to be really noticable, but I do love how planted the 197 is at speed its a lot better than gti, st, fr etc Ive driven. Cant really say if its the chassis or diffuser but it feels a class apart!

 

[Mike]

it does do something, ive heard its around 40kg of downforce at motorway speeds.

this is only what ive heard, cant be arsed to research it tbh

I too have heard that!

But I have a spare wheel in my boot so that must add a few more KG down force

 

[harleybarley]

just found this googling clio 197 images at work (im bored and need to choose a colour!)

 

[Swervin_Mervin]

This is why. Not a great deal to do with the diffuser at all (the claims made on the diffuser increasing downforce are garbage imo)

 

[pturner3]

Think this is to do with boundary layers and the fluid frictional resistance component of the total resistance.

The boundary layer at the car body will show laminar flow (as opposed to turbulence). This layer will be almost stationary, right on the body shell surface, compared with the free stream velocity (turbulent depending on speed and viscous forces) experienced the further away. - i.e. - the dirt will be swirling around in the moving air, but is exchanged with the boundary layer air closest to the shell, and hence has time to settle on the bodywork.

The CFD image by Harleybarley shows this very well.