External air curtains
 

Throttle stop drag tested, tuft tested and pressure tested. The most effective 'simple' modification for measured drag reduction that I have done.

https://www.youtube.com/watch?v=lSN2vQE_WPs

The best candidate I've seen, from Ecomodding Central. I suggested he search on 'edgarwit':
https://i.gyazo.com/79057290b82dffb3...01cc2a8e68.jpg
https://ecomodder.com/forum/showthre...eas-38904.html

Awesome.

I appreciate you trying new things and testing them rather than dismissing them as something only large corporations with vast resources and staff of professionals can do.

And why does it look so ugly? The modifications must be applied in such a way as to be related to the current design of the car. It's like they're taken from the truck ...
I would have chosen the solution inspired by Mercedes-Benz A-Class/C-Class.

Well when you do so, you can show us the results.

That's a section of aluminum extrusion. I consider it proof of concept.

It is totally useless in this case. An aluminum (or any other material) sheet does the same thing.

You'll have to show us the results of your testing - this is an interesting area.

Vman455 told me he used sheet metal for external front air curtains and recorded a drag increase on his Prius - but they gave much better stability when passing trucks.

As I say, I'd love to see the results of your tests.

Yes, this is correct--the sheet metal front ducts by themselves appear to increase drag based on fuel economy testing. But when I compared pressure difference on each side of the car just behind the front wheel arches (at Julian's suggestion--thanks!), I found that the average pressure difference between sides in a 25 mph crosswind was nearly 15% lower with the ducts on. The wing sections seem to be a better solution, and something I'll probably try in the future.

Can you post a comparison of the two approaches?

I speculate that a flat plate would have critical angle-of-attack and positioning criteria. I further speculate that a curved plate would approach the result of the airfoil section.

I've been thinking about air curtains on a Geo Metro. It looks like I could add a partial diverter on each side (flushed out to the upper bumper) with curved plates capping the void created.