AlfaRomeo 159 HeadLight AeroDynamics.

[wickydude]

The air flow is not as bad as you think, IMHO.
you can see a rubber profile on top/behind the headlights, that the bonnet rests on.
Air flow through there will be minimal.

[emre2blue]

I don't understand what you meant, I'm sorry, can you mark the picture where is minimal air flow. I think there is non air flow through lights or the case of the headlights.

[wickydude]

by "minimal" I mean "only a very small amount".
As said before, The 159 headlights create an area with higher pressure, aerodynamically making it seem like they are enclosed in glass like other brands.

It means that there is little or nothing to be gained by changing the headlight units.

[emre2blue]

Ohh! I see now. But does it better to make flow away, than build up some pressure?

[RedDevil]

Pressure is what moves air aside. The advantage of having a high pressure area ahead of your head;lights, or car in general, is that it moves the air aside without any surface friction.
That's why a blunt nose is more aerodynamical than a sharp one, at least at speeds well below the speed of sound.

If the lamp units were in a smoothly curved area then covering them over would help, but the hood and side pannels fold sharply away so that does not matter here.

[aerohead]

Originally Posted by emre2blue

Ohh! I see now. But does it better to make flow away, than build up some pressure?

The headlights are in a very favorable pressure gradient regime,with air attacking all around the lights location.And with enough surrounding radii,and stagnant air pooling inside the headlight bucket,the surrounding free flow should just glance off the area without separation.
I suspect that the air is already displacing into streamlines well in advance of the nose anyway.
Most wind tunnel photos reveal this Prandtl line of discontinuity as the air attempts to avoid sharp accelerations.