mercedes new c-class aero tail-lights

[vis]

I read here and there that the new mercedes c-class has some cuts into its tail-lights to improve aerodynamics by reducing drag.
I actually saw this particular with my own eyes, and these cuts are long and narrow rectangles along the outer and lower part of the tail-lights.
Unfortunately at the moment I don't have any clarifying picture about.

Can anyone explain how this trick could cut drag? Thanks.

[joseff]

They're basically vents to help fill out the vacuum behind the car.

[zac510]

I'd like to see a picture.

[Phoenix]

I have a feeling that this is what you are talking about Vis.

http://www.worldcarfans.com/rsslink.cfm ... ail-lights


Here is another picture


http://www.worldcarfans.com/news.cfm/ne ... s-revealed

[ginsu]

Neat idea. I think this is a similar concept to flaps, where they are taking high pressure airflow from one surface and injecting it into the boundary layer on a surface with low pressure airflow. This should add 'energy' to the boundary layer delaying flow separation from the surface. Delaying the flow separation allows 'pressure recovery' from a rearward facing surface and should reduce the drag of the vehicle.

[allan]

whether it cuts drag or not, i really hate the way it looks!!!
who would pay 40,000$+ for a car that looks like a kia reo?!!!

[joseff]

@ginsu: from your pics it looks to be forcing the boundary layer to separate instead of keeping it attached.

@allan: Don't worry, this means more affordable used W203's for everybody

[DaveKillens]

Safety and visibility were two priorities in this design. It is important to keep the rear taillights as clear and visible as possible, and this design restricts the ability of road dust and dirt from collecting and obscuring the lenses.

[scarbs]

Surely, to keep the tail lights clean you want attached flow over them! it appears the flow is being detached before the lights with the vents on, rather than trying to follow the curve inward behind the car.
My first thought when looking at the CFD image was that more of the rear of the car would get dirty as no flow is flicking over it. I recently had a Vectra for six months and the tail got filthy as the rear end was so bluff.

[zac510]

Most cars will do that if you don't clean them for 6 months scarbs

I guess it was easier for Merc to put this shape into the tail lighting than into the body styling.

[Tom]

Her's an idea, merc wanted a sporty look to their car so they descided to put some 'go faster' vents at the back. They had a choice, put the vents into the metal rear quater panel which is a single piece along with the floor, pillars and roof, cut a hole out of the rear quater panel and put in a plasic vent or cut the vent into the perspex light cover? The last option proved to be the cheapest and easiest to do so they descided on that. Its nothing to do with aero, its all marketing.

[joseff]

Yes, but will it help with brake cooling?

[ginsu]

@ginsu: from your pics it looks to be forcing the boundary layer to separate instead of keeping it attached.

From that picture, it looks to me like more of the tail light is obscured in the low drag configuration. It is hard to see, but the pic w/o the vented tail light shows the airflow getting caught up in vortex, i don't think it's following the curvature of the rear surface, but has already detached when it gets pulled into the vortex. But, yeah, it's hard to know for sure from that one image.