Hi!

I watched the TBO cars at high speeds in force view, but i couldn't see any downforce forces. Perhaps i am wrong, but then what is the rear wing for?

looks

like most cars that look like that .. ei: supra.. big wing, no downforce (that i know of atleast)

Those things are spoilers rather than wings. They don't generate downforce but they reduce the production of lift (and also increase drag slightly).
Look at the side profile of a car and you'll see it looks roughly like an aerofoil (flat on the bottom, curved on top).
This means that cars generate lift at high speeds which can cause serious handling problems!
Spoilers do exactly what the name suggests, they spoil the airflow over the rear of the car by causing the boundary layer to separate earlier (ie somewhere over the rear window rather than at the edge of the tailgate). This causes a reduction in the size of the low pressure area at the rear of the car and reduces the lift. It does increase the size of the wake, however, so there will be a small increase in drag.

Look at the Audi TT...they had problems with the original design generating too much lift at high speed. If I remember correctly a couple of people in Germany were killed when the rear end lost traction and spun the car at high speed. The designers added the little spoiler on the rear of the car to reduce this lift generation.

Just done a quick search...this link gives some more detailed information:
http://www.caranddriver.com/ar ... _id=4&article_id=3523
The article says that the original TT generated 148 pounds of lift at the rear axle at 125 mph. With the spoiler fitted this is reduced to just 53 pounds of lift.

So, in short, they should have an affect, but since body lift on the road cars isn't modelled yet, they don't really serve a purpose anyway (and any downforce they might give by modelling them without modelling the body lift would be useless since they wouldn't be adding any grip to the front wheels - in fact they'd probably be removing some (due to being positioned behind the rear wheels)).


Edit:
Getting off-topic, but to put the lift from the TT into perspective, it was generating the same lift as the rear wing of the Formula V8 at 4 degrees (though obviously to generate positive lift the wing would have to be mounted upside down). Or the Formula XR rear wing at 6.5 degrees (that's a smaller wing).

With the new spoiler it's like reducing the wing angle from 4 degrees to zero (or from 6.5 degrees to 1). Quite a change.

All the other cars in the report generated lift inbetween that of the TTs (with or without the spoiler)

Yeah, they should have an effect but you wouldn't model them as individual wings, you'd just change the lift/drag coefficients of the whole car body.

Those calculations you did on the comparison with the FO8 rear wing show how effective spoilers are. The real beauty of a spoiler comes in the drag figures though... At 125 mph and 0 degrees AoA (TT with spoiler), the FO8 wing generates 87 Newtons of drag and at 4 degrees AoA (TT without spoiler) it generates 102 N. That's over 17% drag increase, while the typical increase in drag from adding a spoiler is of the order of 5%, usually less.

Thanks for the detailed answers StewartFisher and Bob Smith, now it's clear for me how the spolier (and not wing ) works. And it's clear that it's not a bug, the spoiler doesn't generate significant downforce.
Btw, I wonder if the body lift will be modelled in S2 (in road cars)? Until then, those spoilers just for looks .