This is what BMW says on side vents or what BMW calls them -"Air Breather" for the new 4-sereis coupe, which also features these vents and the Air Breather will be a design feature in all new BMWs.

The Air Breather, an aerodynamically effective aperture behind the front wheels, offers another pointer to the sophisticated aerodynamics of the BMW Concept 4 Series Coupe. It draws a dynamic path between the two light surfaces of the car’s flanks, replicating the prominent form of the stylistic front-end elements. The Air Breather brings together the priorities of BMW EfficientDynamics and time-honoured BMW design, and works in tandem with the Air Curtain in the front apron to ensure an effective reduction in drag around the wheels.