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bluebrakes

Drag Coefficients

You can improve/worsen aerodynamics, vehicle Cd (in percent)...

Lower vehicle by 30mm..............-5%
Smooth vehicle covers.............. -1 to -3%
Wide wheel/tyres..............+2 to +4%
Windows flush with body.............. -1%
Seal body gaps..............-2 to -5%
Underbody panels including undertrays, etc.............. -1 to -7%
Concealed headlamps (like an old porsche).............. +3 to +10%
Door mirrors .............. +2 to +5%
Airflow through radiator.............. +4 to +14%
Brake cooling devices.............. +2 to +5%
Open windows.............. +5%
open sunroof .............. +2%
interior ventilation .............. +1%
Roof Rack.............. +40% (JUST THE ROOF RACK!!!)  

now who thought undertrays and lowering vehicles weren't important!  
loomx

From what I remember a standard S4 has exactly the same drag as an E60 M5.
bluebrakes

really?!
loomx

Yup it might actually have been 0.01 better, its definetly better than the M6! Shocked me when I found out that the M5 has a lower drag than an M6
DavidT

Moved to general car chat because it't about cars

Can you post up some figures for Audi's and similar other cars please?
loomx

I found them out from tech docs at work, I will have a look when I go back.
bluebrakes

BMW have it on their website anyway.

supposedly from digging around on a few websites,
s4 b5 -> cd 0.31
RS4 b5 -> cd 0.34

The new M3 saloon -> cd 0.31
The new M5 saloon -> cd 0.31
The new X5M -> 0.38
M6 Coupe -> 0.32
Porsche 911 Carrera -> 0.29

A tear drop is the most aerodynamic shape. Porsche more or less follow this shape.
loomx

Sweet I remembered correctly
DavidT

Hmm, E60 M5 is very slippery for such a big, well tyred car. No wonder they can do 200mph with 500 bhp!

Teardrop is big at the front though!
loomx

It alwaysed shocked me that the M6 isnt as slippery as an M5.

Still that means over 200mph is obtainable on a 500bhp S4
MoRS6+

Just looked up my car ( RS6+ ) - 0.35

Looked up my old car ( D2 S8 ) - 0.29

Looked up new model ( D3 ) A8 - 0.27    

Weirdly, the D3 S8 ( V10 ) comes in at 0.286, but still good (more cooling, bigger wheels I suppose).
DavidT

Saloon or avant on each of the above please Mo?
MoRS6+

DavidT wrote:
Saloon or avant on each of the above please Mo?


Well the RS6plus only comes in Avant and the A8/S8 only comes in saloon form AFAIK.

FYI the C5 RS6 saloon is 0.34
The C6 RS6 Avant is 0.35
And C6 RS6 Saloon is 0.31
loomx

B5 Passat Saloon -> 0.27!!!!!!!
New Passat Saloon -> 0.29
Passat CC -> 0.30
Audi 100 -> 0.30
Audi A2 1.2 TDI - 0.25
B5 S4 Saloon-> 0.31
B5 RS4 -> 0.34
B6 S4 Avant -> 0.30
B7 RS4 Saloon -> 0.31
C5 A6 -> 0.28
S3 MK1 - 0.34
BMW E90 3 Series -> 0.29
BMW E92 3 Series -> 0.28
BMW E39 M5 -> 0.29
BMW E46 M3 -> 0.32
BMW E46 M3 CSL -> 0.33
BMW Z3M Roadster -> 0.43
997 Carrera S -> 0.27
Cayman S ->0.28
997 GT3 ->0.29
Lamborghini Gallardo Superleggera -> 0.34
Mitsubishi EVO VI -> 0.35
Pagani Zonda C12S 7.3 -> 0.40
Koenigsegg CCR -> 0.35
Honda S2000 -> 0.38
Clio V6 - 0.38

F1 Car -> 0.70 to 1.1 depending on setup.

A few interesting ones there!
bluebrakes

that's the thing with aerodynamics. Just because a car has a higher cd doesn't mean it's down to poor design,etc

An F1 car has a high coefficient because it utilises so much downforce. Supposedly an f1 car can stick to a roof of a tunnel because of all the down force from the splitters, spoilers, etc.

So a higher cd isn't necessarily a bad thing.
MoRS6+

Re: Drag Coefficients

bluebrakes wrote:
You can improve/worsen aerodynamics, vehicle Cd (in percent)...

Roof Rack.............. +40% (JUST THE ROOF RACK!!!)  :shock


Anyone know how to remove the roof bars on an RS6 Avant?!    
loomx

Those roof bars might not increase the Cd.

The ones on the MINI clubman actually reduce the Cd.
leaking headgasket

The Mercedes-Benz 190E 2.3-16 (Cosworth) had a good Cd for its time iirc.
Same goes for the VW Corrado.
DavidT

bluebrakes wrote:
that's the thing with aerodynamics. Just because a car has a higher cd doesn't mean it's down to poor design,etc

An F1 car has a high coefficient because it utilises so much downforce. Supposedly an f1 car can stick to a roof of a tunnel because of all the down force from the splitters, spoilers, etc.

So a higher cd isn't necessarily a bad thing.


True, but very few road cars generate any meaningful downforce, so what you're left with is comparing CD figures.
loomx

Depends, at the end of the Cd isnt really much to go by, a basic bottom of the range A4 will have better Cd than an S4/RS4 because wide wheels and cooling ducts cause more drag.
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