Why Cd vary so much within same models of car?
 

VARY CD
CLA C117 drag coefficients vary from 0.22 to the 0.30, depend on model/engine/equpiment.
Is is possible that Cd vary so much just for tiny differences at each model if car outline/siluetthe is the same?

I allways thought that you must completly change car body shape to jump from 0.22 to 0.30


LIFT
CLA front and rear axle lift at 70mph is 46 and 44 pounds, that mean lift is 4 times bigger at 140mph, overall 360pounds(163kg)!

Can car produce so much lift or this is normal values for cars?

I cant post links so google this :
Five slippery cars enter a wind tunnel - Tesla

M-B CLA Cd variability
 

If this link works, you'll find a list of aero optimizations specific to the CLA 180 Blue Efficiency which explains the difference.
http://https://www.car-engineer.com/...-of-the-world/

Link dont work..

failed link
 

try a search for:
Mercedes CLA is most aerodynamic production car in the world:)

What do you think about this lift numbers?

The reason your links fail is the doubling up of the component tags, as bolded. HTML ignores malforrmed expressions and moves on.

CLA lift numbers
 

Are these the values that CAR and DRIVER published in their 'Drag Queens' article, relating to the A2 Wind Tunnel measurements?
If so, I'm all in on what they measured, and the lift would be exactly as you've reported for 140-mph, as we're talking about the square of the velocity.
A CLA 180 Blue Efficiency, with five passengers and there luggage, for it's total weight, at 140-mph on the un-regulated portions of the Autobahn, even at 360-pounds of lift, I don't know that a driver would even 'feel' the lift.
The CLA grosses out at 1850-kg ( 4077.95-pounds )
Subtracting the 360-pounds of lift relates to a 8.8% change in mass.
I drove the Autobahn in 1997 and when I drive, I'm paying attention.
At 3,717-pounds on the wheels, I think I'd be okay with the 'lift.'

I dont know in which wind tunnel is meassurments done..
CLA has 1480kg, Merc. claim 180 blue efficiency has Cd=0.22 and 250CDI in test has shown Cd=0.30.
This two cars are 99.9% identical, to me is strange so big difference in Cd.
What do you think?

"This page doesn't seem to exist."

Message is apparently browser dependent. Chromium:

Kill the first htp:// and the second / on https, add a : after the htps

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

Works in opera with security on. OR you can go to www.car-engineer.com and just do a search

The htp:// is an undefined web node caused by quoting something on this site? I believe it is part of the underline and change color or font process so it is clickable because you will notice my corrected string does not direct you to the site.

It's easier than that.

The URL entry field comes prepopulated with 'http' preselected. Press right arrow or click in the field to deselect and paste and you get doubled up tags. One less action to make it work.

so big difference in Cd
 

Did you look at the nineteen detail optimizations specific only to the CLA 180 Blue Efficiency?
If each modification produced a drag reduction of only 4.2-counts, together, we'd have the delta- 0.08.

Yes but 180 model(without BE) has 0.23, so it seems all this features reduce just for 0.01...

other source
 

Researchgate had some info:
CLA 250 Euro-spec, Cd 0.28
CLA 250 USA=spec, Cd 0.30 @ A2 Wind Tunnel ( Don Sherman, CAR and DRIVER )
M-B B180 Blue Efficiency with eco package, Cd 0.24
CLA 180 Euro-spec, Cd 0.23
CLA 180 Euro-spec Blue Efficiency, Cd 0.22
--------------------------------------------------------------------------------------
The A2 Wind Tunnel measurement would not compare to any M-B measurement.
--------------------------------------------------------------------------------------
baaf_ks.com reports that 230,000-hours of wind tunnel time was spent on the Cd 0.22 variant.
--------------------------------------------------------------------------------------
Some of the reporting is so non-specific, I'm no longer sure what the journalists are actually reporting.
Ideas?

Where can I find drag coeficient of CLA C117 180CDI?
(where did you find this numbers)
It is very hard to find this numbers, they only report 0.22 for BE and 0.23 for "others models "in CLA class..

I still cant post links...

where?
 

WIKIPEDIA credits the CLA Coupe (C117) CLA 180 CDI ( 107-hp ) Euro-spec Blue Efficiency with Cd 0.22:
* A-pillars
* Exterior mirror housings and rear shape
* Diffuser
* Underbody
* Radiator shutters
* Wheel trim
* Serrated wheel deflectors ( all for wheels )
* 205mm section tires
--------------------------------------------------------------------------------------
The Cd 0.30 is from Don Sherman @ A2 Wind Tunnel, and has been called into question by some ( the Toyota Prius also tested, recorded a higher Cd than what Toyota measured, same for the Honda Insight and Nissan LEAF ) Only the Tesla S registered a Cd equal to it's published value [ then some report that Tesla's value was actually Cd 0.26! ].
The CLA 180 Euro-spec BE car isn't available in the USA. They must have tested something other than the Cd 0.22 variant.
A real can of worms!

CLA C117 180 Blue Efficiency with diesel engine? (I thought only comes with petrol engine.)

Why I cant find any 180 cdi or d Blue Efficiency on internet to sale??

'diesel'
 

Does 'CDI' stand for 'Compression Direct Injection' ? I'm not familiar with Daimler's nomenclature.
Whatever engine produces 107-horsepower is supposed to be the Cd 0.22 car's engine.
Seven (7) engines and two (2) transmissions are available for the CLA, however, only the 107-hp engine is in the Cd 0.22 version.

9

10

11

12

13

14

15

Now I can post links!

CDI=Common Rail Diesel Injection

Petrol engine 122HP also has 0.22, CLA 180 BE

https://www.automobile-catalog.com/c...html#gsc.tab=0

The real kicker to all of this is why does the Hyundai Ioniq have the same Cd in its hybrid version and the EV version? Clearly a smooth undertray and fully blocked front grill shoukd lower the drag versus a messy under floor and front grill…

....and we know how many posts it takes now. Thanks!

Yes ioniq 6 looks more aerodynamics then cla
cla BE has closed floor with panels but exhaust is exposed...

How’s Mercedes’ eqs ev only 2 drag points under the cla blue? Whole resign of the body and smooth grill and flat under floor. Yet only 0.02 drag reduction?

Maybe is not going linear, lower you go, harder to get every point..
?

Also off road packages and tires don't change EPA ratings even though they clearly affect gas mileage. So they get to use the same aero numbers even with big flairs, larger tires and a 4" lift. A Ram 1500 with Rebel package get the same rating as a standard Ram 1500.

Similar with 2 models built on the same platform like a Lincoln MKX and a Ford Flex. The MKX has better aero but the epa let's Ford rate them identical maybe so they don't compete with themselves?

It's almost like base reality filtered through a political process become distorted? First time? :)

'big difference'
 

In 2013, BMW's i8 also registered Cd 0.22, in CFD.
Kalheinz Ebbinghaus, aerodynamics engineer on the BMW i8 commented that ' Thirty to forty percent of a car's aerodynamic resistance is created in the wheels and housings,' ( up to Cd 0.088 with the i8 ).
That easily covers the variability of the CLA if we ignore the A2 Wind Tunnel data. And I recommend we consider only numbers from the M-B tunnel.

Hyundai Cd
 

http://https://ecomodder.com/forum/s...0-a-24646.htmlI don't believe that KIA/ Hyundai / Genesis reports complete drag coefficients.
There brochures report identical Cds across all optional equipment, which wouldn't occur in the real world.
And different tunnels produce different numbers.
I'd relegate the 'Drag Queen' values to some special case They're not cross-wind averaged, as would be the case for the maker's coefficients.
I suspect that we'll never obtain all the data we'd like for the CLA.
We 'fully' discussed the CLA here at the AERO Forum nine years ago.

Yeah, sure. Only Ford reports correctly.

CLA has 0.22(180 BE) and 0.23(180), CLS C218 has 0.26, but CLS has wide tires, no flat bottom etc.

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.

cls
https://thumbs.dreamstime.com/b/side...-232195598.jpg

cla
https://www.mad4wheels.com/img/free-...013-379557.jpg

' M-B body shape'
 

1) The 2008 M-B Bionic Boxfish is the most efficient shape Daimler has produced.
2) The 2018 M-B A-Class is the second-best design.
3) The 2013 M-B CLA 180 Euro Blue is in third place.
4) There's nothing to prevent a CLS from being streamlined to a drag lower than a CLA 180 Euro Blue, but that would be on the owner of the car.
5) According to Dr. Teddy Woll of Daimler, the tail by itself could take the CLS down to Cd 0.221, with no other modifications.
A set of 4- wheel covers, like on the rear of the Koenigsegg Jesko Absolut would take the boat-tailed CLS below Cd 0.20.