Compare aerodynmics of two cars

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SUMMARY

The Mercedes CLA has a drag coefficient (Cd) of 0.22 for the 180 Blue Efficiency model and 0.23 for the standard 180 model, making it one of the most aerodynamic production cars. In contrast, the CLS C218 has a higher Cd of 0.26, attributed to its wider tires, lack of a flat bottom, and other aerodynamic features. While the CLS has a more streamlined silhouette, its design elements, including a larger frontal area and increased weight, contribute to higher drag and fuel consumption. Modifications to the CLS, such as using narrower tires and a flat bottom, could potentially improve its Cd, but it would still likely consume more fuel than the CLA.

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Jurgen M
Mercedes CLA has Cd =0.22(180 Blue Efficiency) and Cd=0.23(180).
CLS C218 has 0.26, but CLS has wide tires, no flat bottom and other aero features like CLA.

aero features of CLA:
https://www.car-engineer.com/mercedes-cla-is-the-most-aerodynamic-production-car-of-the-world/

If we compare just body shape ,do you think CLS has better Cd from CLA, for example if we put narrow tires, flat bottom etc maybe CLS will have even better Cd then CLA?

I ask this because CLA is short, rear roofline looks to stubby, rear window+trunk slope is too steep,this can cause flow separation or too steep slope induce low pressure at rear window+trunk.

CLS is longer, more streamlined siluetthe,rear end slope is not so steep.

all-building-facade-moscow-russia-august-232195598.jpg
mercedes-benz-cla-c117-45-amg-2013-379557.jpg
 
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Jurgen M said:
...
If we compare just body shape ,do you think CLS has better Cd from CLA, for example if we put narrow tires, flat bottom etc maybe CLS will have even better Cd then CLA?

I ask this because CLA is short, rear roofline looks to stubby, rear window+trunk slope is too steep,this can cause flow separation or too steep slope induce low pressure at rear window+trunk.

CLS is longer, more streamlined siluetthe,rear end slope is not so steep.
Modifying the CLS C218 car, you could reduce the factory's Cd.

1) The CLS has wide tires because it weights around 1950 kgf, compared to the 1540 kgf of the CA.
2) It also has a frontal footprint area about 4% bigger than the CA.
3) Being longer, it has more drag caused only by skin friction.

Because those three factors mentioned above only, it will still use more fuel after you improve its Cd to match the CA's Cd of 0.22.
 
Lnewqban said:
Modifying the CLS C218 car, you could reduce the factory's Cd.

1) The CLS has wide tires because it weights around 1950 kgf, compared to the 1540 kgf of the CA.
2) It also has a frontal footprint area about 4% bigger than the CA.
3) Being longer, it has more drag caused only by skin friction.

Because those three factors mentioned above only, it will still use more fuel after you improve its Cd to match the CA's Cd of 0.22.
I mean if we compare only car body, which will have better Cd..
 

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