Forums

JOIGNEZ-VOUS À LA COMMUNAUTÉ
INSCRIVEZ-VOUSIdentifiant

Industry-leading drag coefficient boast...well, it was good while it lasted.

Apparently the new 2014 MB CLA250 has a drag coefficient of .23

(and a hell of a nice looking car for under 30k to boot!)

http://www.motortrend.com/roadtests/sedans/1301_2014_mercedes_benz_cla25...

Comes out in Sept., so I guess we have another 8 months or so of leading the field in that department left.

ehhh....
I don't like anything with tailpipes....
I'll take the Model S anyday over this car.

Great challenge to make the X 0.22 and Gen3 even lower. Elon will love this... Just the kind of engineering he wants from his guys.

Soooo many buttons.....

I know. The buttons were actually nauseating to me. Amazing how quickly my tastes have changed.

Also, is that a trunk or a glove box in back? ;)

Still has handles :-)

meh...

The driver's side window and mirror controls look familiar though...

ugly outside, fugly inside.

Is that a Dodge Charger front?

I hate analog speedometer.

Scattered, unorganized center console.

Hey! It has Model S windows and side mirrors controls!

I think the LCD display looks tacky, like it's an add-on or something, not like something integrated into the vehicle. And I agree, too many buttons. The dash looks cluttered.

Jesus, it's like a piranha tank in here!

Cd is the ratio of apparent frontal area to actual frontal area. So the Tesla has air drag equivalent to flat plate with 24% of the actual frontal area of the car.

The Model S is a lot bigger car than the MB shown and wetted area is part of drag. If the MB were as big (long) as the Tesla it would have a higher Cd, I believe.

Does it say under $30K? I looked up in MB site as well. No mention of price..

DTsea - that's interesting to know.

pvenkate - http://www.forbes.com/sites/rebeccalindland/2013/01/17/mercedes-benz-unv...

"Pricing will range between $29,999 and $35,000 so as not to cannibalize sales of the $35,350 C-Class."

After owning a 2000 S-class for over 12 years, I can say from personal experience that any claim made by Mercedes should be closely scrutinized. Information provided to me on multiple occasions had a "high fiction content" to quote a CEO familiar to us all.

@DTsea, a bit wrong explanation, CdA is a drag coefficient with a frontal area in the calc, Cd is the modifier to that. The lower the Cd the better.

Does anybody know for a fact what the Model S Cd is? 0.24 is commonly accepted number, but AFAIK that is just estimation.

Drag coefficient is a claimed number, but nobody really confirms it. Check out the wiki list, EV1 is still #1 with claimed 0.195.

In case you follow F1 - windtunnels are notoriously blamed for not being calibrated properly. Mercedes didn't do well in F1 the last 3 years... maybe due to their windtunnel.

Wind tunnel test could confirm it. Measure drag and add the frontal area = CdA.

@Timo | JANUARY 30, 2013: Measure drag and add the frontal area = CdA

In case anyone is interested, I measured the frontal area using the Tesla S web image (http://www.teslamotors.com/sites/default/files/images/models/options_top...) and calibrated the pixels to meters using a neat free program called ImageJ (http://imagej.nih.gov/ij/index.html). The resulting area is 2.676m**2. CdA is therefore 0.24*2.676=0.64224. This can be used in Web programs, such as GreenRace (http://www.jurassictest.ch/GR/) to update the SCx value for the Model S.

If you want to recalculate the frontal area, use the following sequence in ImageJ:
File->Open...
Image->Type->8-bit
Analyze->Set Scale... Distance in pixels:245, Known Distance: 2.18948, Unit of length: m
Analyze->Analyze Particles... Show: Outlines, Display Results
(Results Window displays area 2.676m**2 and an outline of the shape is also produced for verification)

I've owned a dozen MB's, and have a recent SL (a great car). My take on the CLA?

A fatty with a face lift.

Granted, a different market segment, but compared to the Model S, this future MB already looks old.

MB needs some fresh blood in design and engineering.

There are some grateful guys in California who'd be happy to help.

Timo, drag=(.5)*(air density)*(velocity squared)* Cd

The flat plate metaphor is an explanation for the layman, true, but since the true flat plate drag is irrelevant, it is explanatory. Calculated drag includes (for low Mach number) form drag, skin friction drag (wetted area and surface property driven) and excrescence drag (door handles and other protuberances). In practice computational fluid dynamics give good estimates for form drag, but total drag is usually determined from the wind tunnel and (for cars) the Cd is back-calculated from drag.

But that's all kind of a lot of explaining so I just shared the flat plate metaphor.

So said professor Harris back in undergraduate aerodynamics class. I hope I understood it right when I was grading all the juniors' aero homework when I was a grad student.

Cheers-

@DTsea,

Nice to see a fellow aerodynamicist on the forum.
@Alex K, and @Timo, are you also in this field?

Good analysis.

Back to the topic: I just visited the link for the CLA250.
From a cursory look at even the front end, @Robert22 may have a point.

Regarding looks, without actually seeing it 'in the flesh', the 250 has a decent looking body. The Audi A7, though, looks much prettier, but our Tesla S still leads the pack.

As for the original concern, when the smaller Gen III comes out, as has already been explained, it should be easier to lower the drag for a smaller car.
Fortunately, the S has so many positives, only one of which is the drag crown.

- best.

P.S. The 'drag crown' I mentioned was for a King, not a ...

- best.

@Alex K

When you plug in your numbers to the jurassictest site, does it increase or decrease the Model S range? By how much? Do you think your estimate is better than the one on the site?

"Mercedes will also offer a raft of performance technology such as its Collision Prevention Assist, which works at speeds above 4 mph. This radar-based braking system can warn drivers of a pending accident and pre-charge the brakes to create faster braking abilities. The CLA-Class lineup will also offer Distronic cruise control, lane keep assist, and blind spot detection system as part of a Driver Assistance package. "

TM, please make this as options soon ..
Almost every other premium sedan have simular options..

Sadly it's a fossil fuel car...

Nice of them to put all the crap in the same package so it is easy to avoid it :)

Tesla, Nissan, even Ford are moving us into the future. I get excited reading about, driving a Tesla. Gas cars are, not yesterday but, just not where I want to go. The Tesla Model S is paradyme shifting, bringing on the future....soooo awesome!!

Tesla has all that. It's called 'human eyeball and brain.'

I personally would not pay extra for all the 'safety' things. My wife would. Each to their own I guess.


X Deutschland Site Besuchen