Air Curtain
 

http://www.bmwblog.com/wp-content/up...ir-Curtain.jpg

"The new Air Curtain is the latest innovation BMW aerodynamics. First introduced in the BMW 1 Series M Coupe, Air Curtain now would be a standard feature on the 128i Convertible. Air curtain increase airflow around the front wheel arches with the benefits of turbulence are significantly reduced."

I would love to see some DIY takes on BMW's latest innovation.

My impression is that it is more of a marketing too. Sorta like hood scoops that are not connected to the intake or most rear located spoilers on sports cars. Just my humble opinion but I am always open to being shown different.

Randy

I have those suspicions too. Ducts generally don't increase aero efficiency, even if these things aren't exactly long ducts. There is a chance they are on to something- they have the wind tunnel after all. We'll see if this strategy becomes commonly implemented...

Corner scoops / air guides are fitted to just about all European cab-over-engine trucks.
This looks like it's doing the same on a smaller scale, then using the scooped air to blanket the wheel arch like an invisible front skirt.

I don't see why it should be disregarded.
These guys have their own pretty modern windtunnel.

Most new cars around here have them. But the scoops are blanked off! lol!!
I expect the drag created on the functional ones will be offset by the drag reduced by the air curtain. Watching this space.

my observation on these is that they are near the sides of the grill only wich makes me think they're there either get more air into the grill or less at speed when you might want the air to go round them. i think the primary goal is cooling however, given the overall lack of attention to aero on these trucks with square corners sticking into the airflow everywhere.

that said i wouldn't just dismiss the bmw setup as just marketing, it's usually little details that cause little changes in drag. in fact the new ford fiesta over at the parking lot at work has two open side scoops that lead into the bumper and i think there's some vents in the front fender too. could be the same thing.

when looking at the bmw efficient dynamics concept there's something interesting too

http://i77.photobucket.com/albums/j5...-car-walls.jpg
the car seems to have some sort of scoops on the front and this picutes shows theres actual clean ducts to the wheel wells and not radiators or whatever
http://i77.photobucket.com/albums/j5...ynamics_15.jpg

seems like the same thing going on there

The air curtain is pretty small but effective in reducing drag at speed (albeit .01%, but every bit helps)

Euromodder is spot on, the scooped air is being used to blanket the wheel arch like an invisible front skirt.

View of the slots on the M Coupe.
http://www.caranddriver.com/var/ezfl...cd_gallery.jpg

Reverse angle.
http://farm6.static.flickr.com/5088/...0c348e70_z.jpg

Somewhere on internet I have seen these mounted on big rigs. I think the theory is that they turn the air around the corner, preventing separation & the drag associated. The ones I saw were mounted on the front corners & above the windshield.

The Iveco ECOSTRALIS & Scania hi-box trucks have these corner deflectors that help cut side aero resistance. It is supposedly more important on crosswind aero and yaw dependance drag. The side deflectors work to diffuse the tall vertical bluff-cornered boxes.
Maybe it works like a race car side ducts, 'in front'. Wheel wells traps so much turbulent air from counter tire rotation, engine bay & brake heated air. Opposite a typical corner canard, the front vertical airflow reduce the pressure difference & air stagnation inside the bay.

ECOSRALIS Aerodynamic Kit

claim
 

There might be a specific context in which the full spirit of their claim is captured.
If you're burning,and someone throws gasoline on you,there will be a localized cooling effect,but you're still on fire.