Mercedes beats Tesla - New CLA has cd of 0.23!

[Norbert]

Thanks, Todd. Here's a similar discussion we had about 14 months ago when the Model S was said to have a Cd of .22: CNN Money interview with Elon

One has to see if the final production version will maintain the Cd, or go up like the Model S did.

Of course it's a matter of opinion, but to me the Model S looks much better, and since with 208 hp the CLA isn't very performance oriented, and the mpg efficiency is unknown (yet surely not as good as that of an electric car), the Cd value doesn't seem to really contribute to any significant feature of the car. So what's the point?

 

[Todd Burch]

http://paultan.org/2013/01/14/new-mercedes-benz-cla-class-makes-its-debut-in-detroit/

Hope this helps.

My point is that the Model S may indeed have a "more slippery" design--and I think it does. When people ask why the Model S, with it's limited frontal air intakes, smooth nose cone, flat bottom, etc. looks more aerodynamic than the Mercedes, it's because I think the Model S is in fact a more slippery design.

The Mercedes may have lower drag. But the Model S is a much larger car--not only in frontal area, *but in length as well*. Notice that the *length* of the car is not considered in their "A" area. They only use frontal area, which puts the longer car (Model S) at a disadvantage (more skin friction).

Put another way, Tesla may have a better slippery design *given the size of the car* than the Mercedes. I think it does.

 

[Norbert]

The Mercedes may have lower drag. But the Model S is a much larger car--not only in frontal area, *but in length as well*. Notice that the *length* of the car is not considered in their "A" area. They only use frontal area, which puts the longer car (Model S) at a disadvantage (more skin friction).

That's a good summary. I didn't fully realize the point you were making until reading this.

 

[Discoducky]

They are trying to do their best impersonation of an EV. I'm personally over the look of the Merc's. Audi styling, currently my fav, is getting old as well.

Extensive underbody cladding, additional cladding at the center of the rear axle, an aerodynamically optimized muffler and a diffuser improve the flow of air beneath the underbody.

 

[brianman]

Various: "The CdA is what matters, not the CdA."
Me: "The CdA of the Mercedes is reported as ___."
Various: <silent on the subject of Model S's CdA and how it compares>

/sadface

 

[richkae]

I bet the fact that the Mercedes has 17 inch wheels instead of 21 inch wheels helps it get a lower Cd than the Model S.
Yes I know everyone loves the 21 inch wheels, but those giant wheel openings and giant wheels are bad for aerodynamics.

 

[stopcrazypp]

Various: "The CdA is what matters, not the CdA."
Me: "The CdA of the Mercedes is reported as ___."
Various: <silent on the subject of Model S's CdA and how it compares>

/sadface

Probably got it got buried. We don't know the S's CdA so can't really compare, but having the CLA's CdA is useful. It shows they are assuming A = CdA/Cd = 5.49sqft/0.23 = 23.87sqft.

Don't know how accurate wiki is, but the 99 Insight apparently had a CdA of 5.10sqft (Cd of 0.25), so the CLA doesn't hold the record for a production car.
http://en.wikipedia.org/wiki/Automobile_drag_coefficient

 

[Todd Burch]

Various: "The CdA is what matters, not the CdA."
Me: "The CdA of the Mercedes is reported as ___."
Various: <silent on the subject of Model S's CdA and how it compares>

/sadface

If you're referring to me brianman, I hear what you're saying. I'm not debating that but I was making two points in my earlier post:

One, that aerodynamic efficiency is not indicated by Cd, but CdA.
Two, that although the Merc may be more aerodynamic (less drag), it may not have a slipperier design.

Without actual CdA numbers from both cars, I cannot compare the two, but given the CdA of the Merc, it certainly likely is a more aerodynamically efficient car. But I believe it's primarily because of it's size--the Model S's shape and overall design is slipperier.

 

[smorgasbord]

The real issue for me is that Model S occupants pay the penalty for such over-emphasis on Cd.

 

[PeterW]

The real issue for me is that Model S occupants pay the penalty for such over-emphasis on Cd.

I think you need to qualify that statement in this thread. Unless you have sat in the new Mercedes.