K-A

I'm interested in knowing a bit more about how aerodynamics work.

If you put a W211, W220, W221, and a CLS side by side, obviously the CLS looks like the most aerodynamic of them all.

However, that is way wrong. The CLS gets a pretty "poor" .31 C/D, while the W211 and the two S's all get about a .27 C/D.

That's a pretty big difference.

gaazmon

E55 faster than CLS55. Ya, the E is great and so many people buy the CLS thinking it is more aerodynamic.

K-A

It's so funny, because you'd assume that's the case. I wonder what makes the W211 so much more aero? Probably just a more functional design.

konigstiger

First the 212, now the 219....

K-A

Haha.

Really though, I part next to a 219 and it looks like my car would be pushing against the air more, the 219 seems like it would cut right through easier. Makes you realize aerodynamics are more than just about shape..... Well it makes me realize that, lol, I'm sure many people had already known that by now.

K-A

You gotta hand it to M-B, those mf'ers really know how to make an aerodynamic car.

I recently read that the new BMW 7'er gets a .31 or something like that, and the Audi A5 gets around there too. The W212 is like a freakin' .25, and the Coupe even better. Some of them don't look like total aero mobiles so much (save for the Coupe in this case), but obviously is some engineering wizardry.

220S

Was just reading in the PCA's Panorama Magazine that Porsche made the new GT3 too slippery. So they made some changes to pick up a little more downdraft. They needed some more air to help force the tires to stick to the road.

K-A

Ahh, I was gonna ask about that too. I know Porsche is very **** about Downforce, Drag, Aero, etc. But I'd realized the 911 bodies have a worse C/D than my 4-Door box E. So I assumed, given that, and BMW, Audi, the more performance oriented cars, etc. not going too low in Aero, means that engineering some drag and resistance is good for high speed runs. ?

220S

Yeah a slippery everyday car is great for gas mileage (that's the point in street cars.) But at high speeds you need the car to have some downforce to help keep it stuck to the road. Front splitters keep air from lifting the front and wings in the back help keep the rear down.

That little spoiler on the trunk lid of the AMGs is (theoretically) to force air to push down the rear end. But in reality it's more cosmetic since it's a street car. The GT3, on the other hand, was built to be close to being 100% track ready.

F1 cars are all about wings and wing placement for drag and lift, etc.. (lots of rules on how they can or can't be used, etc..)

gnma

Another contributing factor to the W211 V8's awesome highway mpg

patrick_y

The E has a higher trunk, the CLS has a lower trunk. The higher trunk actually helps aerodynamics.

This requires a lot of understanding of aerodynamic physics. It also helps if you've been in a wind tunnel. You can't necessarily tell by looking at the car.

Did you know, that within the E-Class, an E220, E350, and E550 might have different aerodynamics! I know that within the BMW 3-series coupe, the 328i and the 335i coupes have different Cd ratings.

patrick_y

Very true, all around.

Regarding F1 cars, the FIA actually stipulate where you can put the wings and how big the wings can be. The FIA gives a schematic of a chassis with red boxes, each box is labeled with what can be put on it. It may say wing and dimensions allowed, one box will say this has to be empty space, etc...

Oh, believe it or not, your little wing on the E63 actually contributes a noticeable amount of downforce at high speeds. It looks subtle, but everything helps. Basically, these tiny lip wings increase downforce with almost no increase in drag, so it's a good tradeoff.

Nice to see someone who knows a bit about aerodynamics. You sure can learn quite a bit by just looking closely at an F1 car.

HowardA

Don't forget to consider frontal area

Drag differences through a model range are also down to little things like tyre size & profile and sometimes exhaust system positions.

K-A

Interesting, I always thought a lower trunk meant more Aerodynamics (which is why M-B is sagging the trunks on their cars with new designs), and higher trunks meant more downforce/high speed stability. Ya learn new things everyday.

True about the different models, it has to do with the body cladding I'm sure. I know the AMG body kits lower the CD by .1 or so points.

gaazmon

Very interesting...

155

Slippery or not i would still take a CLS over an E

werewolf34

What about the G class? c/d = 1?

chokaay

More like a 10!

j/k


In all seriousness, this wikipedia article has an interesting chart of drag coefficients: http://en.wikipedia.org/wiki/Automob...s_and_examples

Given that a Hummer H2 has a coefficent of 0.57, I'd imagine the G-Wagon would probably be around there (maybe a little less, but probably in the 0.4-0.5 range).

007_e350

The other day it was foggy here and as I started cruising I observed water vapours curling around inwards from sides of the rear windshield .... very impressed .... this is how rear vaccum is minimized