[RedDevil]

Originally Posted by Cd

As far as the 'scoops' on the sides of the bumpers on cars, some do indeed act as 'air curtains'. In fact, it was even mentioned in the video of the truck about the 'air curtain' effect on the truck (at 2:10 in the video ). What i found interesting though is that they seem to be using the gap in between the bumper and the front end to channel the air around the wheels, versus sealing this gap.

True, just like Mercedes does on the CLA.

Both the Merc and the F150 have a relatively straight front bumper, so I think this is mainly done to shape the overall flow pattern, it may be less effective when the bumper sides are slanted. Not saying uneffective!

The Merc and the F150 have bigger air dams than other cars, another thing that makes the passage through the bumper more effective.
Without an airdam the air trapped under the car will squeeze out through the front wheel wells.
That's why there is so much more brake dust on your front alloys than on the back ones: the air gets forced out of the front wheels and sucked in through the rear ones.
The fronts are not twice as dirty as you'd expect from a front biased brake balance, but ten times so.
The airdam blocks that flow, making the bumper vents more effective. I bet the help cool the brakes too.