[Ls1Rx7]

I've replaced the center section of my Exige 2010+ style wing with a carbon blade, mainly for looks and so that it'll stop bouncing around in my rearview.

Which left me with the original blade sitting in corner, and I started to look at it and say, could I use this spare blade as a track version. Something that's likely ugly but functional at producing additional downforce.

There's a bersion of the Exige 2010 style wing sold by one of the vendors that produces more downforce by changing the AOA of the blade. I don't have those uprights, but if that's functional, it means changing the AOA of that blade will increase downforce.
I also know that Gurney flaps primary method of increasing downforce is essentially changing the effective Angle of Attack (AOA) usually at the cost of drag, but I'm not super worried about the drag with the supercharger.

So I was looking at cheap universal gurney flaps, and you can visualize how these might change the effective angle of the wing and produce downforce and drag:

Anyone have experience with this type of stuff before I start buying ebay junk and riveting it on to my old blade and doing some old school string wind tunnel testing.
If you're not familiar with the string method, see video:

Once I got a shape that looked promising I'd probably skin the whole thing in fiberglass and finish it a bit more. Would be heavy and ugly but I'm looking for effective cheap and easy to install/remove.

 

[TedR]

The wing extension you show on the BMW is not a Gurney flap. A Gurney flap, or wicker bill, is a small tab projecting at ~90 degrees from the wing surface and is somewhat proportional to the chord of the wing. For most wings on an exige, I would not expect a Gurney flap to be more that ~3/8" tall, probably less. Gurney flaps work by damming the air on the top surface of the wing, slowing it, while not stalling the underside of the wing, creating more downforce without adding much drag.

What is shown on the BMW turns the wing into a spoiler by stalling the airflow under the wing. It would be way more efficient to add a second element to a wing, more downforce with less drag, compared to the extension.

 

[shay2nak]

Reverie sells gurney flap for their wings.