Well, considering that Subaru couldn't keep the car together for the 2006 season (poor poor Solberg!), I wouldn't be looking to them for inspiration. Why not Citroen? The Xsara's spoiler (as well as the Ford Focus and most of the other rally cars) all that have that as well.
When I asked what it was for I was told quote, "to clean up the air going over the spoiler". I don't think he meant "clean up" as in emissions j/k.
Notice that the inside of the spoiler is sectioned off every few inches? That's the same thing you do on the underside of the car on endurance cars etc that don't have ground clearance concerns like the rally cars do.
According to my rally mag, it has more to do with the car sliding through the corners. Giving more grip to the rear wheels while a slide was induced. Although Subaru created this design, it's been adapted by the other rally teams.
I wouldn't be looking to them for inspiration. Why not Citroen? The Xsara's spoiler (as well as the Ford Focus and most of the other rally cars) all that have that as well.
Subaru and Mitsubishi's were the only 2 cars that were sedans in the 2006 rally year. They both had the longest wheelbases' and longer overhangs. It has more to do with weight and weight transfer. That's why The new STI is a wagon and a few inches shorter in the overhangs.
Well, I am pretty stubborn so I am going to argue...
Like going sideways for rally cars, where air is not directly straight, wouldnt it be the same case during crosswind situations?
And we all encounter crosswinds. So by putting the vanes in there it will direct air behind the car where it was meant to go and not to the side... ?? So it will keep the airflow behind the car straight back instead of sideways...
The wing is designed for downforce, not reduced drag. So yes, I imagine adding them to a spoiler without them will straighten flow over the wing, but will increase downforce and drag.
From purely intuition, I don't think it will straighten out flow enough to reduce the turbulent region to the side of the car. It might make it worse, since you are increasing the cross-sectional area in that diagonal plane.