Unfortunately, my rich friend is not about at the moment, (some personal issues), so I’ve still not been out in the bright, orange beast yet, but at least I managed to collar him and he’s promised me now…
He was only about for a short while, so this post will be quite brief, but with the weather being quite good, (for a change!), I thought I’d grab the opportunity to take some half decent photos of the underneath. Here you can see how the diffuser is shaped.
I also mentioned in my previous post about this car that it had some sort of J shaped vanes around the wheel arches, so here they are:
If you click on the picture, you can see the full size version. And here’s a close up of the right hand side of the diffuser taken from the rear, so you can see the funneling of the shape. Again, click on the pic and you get a bigger picture to view.
Here you can see how the cross section of the diffuser gently increases and it sweeps up to nearly join the rear body work, where there’s a grille. This is there presumably to let the hot air out of the engine bay, and help cool the gearbox, which you can just about see through the mesh. The air flowing out from here should also help smooth the airflow as it exits the diffuser, preventing too much turbulence forming and therefore further increasing it’s efficiency.
Of course, all of this is total guesswork, as I didn’t study aerodynamics but some of my University friends did aeronautical engineering, so I expect to have my words questioned somewhat at the very least, when they find out about this blog. Or perhaps they’ll just take the rip as usual :-/
Perhaps, it’s at this point I should mention I’ve never really been clear about whether the majority of the downforce happens under the flat bit of the floor, or under the diffuser, or somewhere in between. I can visualise how the diffuser expands the air as it passes through it, increasing it’s volume and thus decreasing it’s pressure. Maybe someone can put me right on this?
The reason I ask, is my friend also has a kit car which I have access to, and it’s bottom happens to be flat…