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Old 11-01-2022, 07:39 AM   #1 (permalink)
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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


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Old 11-01-2022, 01:11 PM   #2 (permalink)
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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/
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Old 11-01-2022, 01:26 PM   #3 (permalink)
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Quote:
Originally Posted by aerohead View Post
If this link works, you'll find a list of aero optimizations specific to the CLA 180 Blue Efficiency which explains the difference.
Link dont work..
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Old 11-01-2022, 02:00 PM   #4 (permalink)
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failed link

try a search for:
Mercedes CLA is most aerodynamic production car in the world
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Old 11-01-2022, 03:21 PM   #5 (permalink)
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Old 11-01-2022, 04:07 PM   #6 (permalink)
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Quote:
Originally Posted by aerohead View Post
try a search for:
Mercedes CLA is most aerodynamic production car in the world
What do you think about this lift numbers?
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Old 11-01-2022, 04:13 PM   #7 (permalink)
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Quote:
Originally Posted by aerohead View Post
URL="http://https://www.car-engineer.com/[/URL]
The reason your links fail is the doubling up of the component tags, as bolded. HTML ignores malforrmed expressions and moves on.
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Old 11-01-2022, 04:28 PM   #8 (permalink)
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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.'
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Old 11-01-2022, 05:08 PM   #9 (permalink)
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Quote:
Originally Posted by aerohead View Post
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?
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Old 11-01-2022, 05:43 PM   #10 (permalink)
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Quote:
Originally Posted by freebeard View Post
The reason your links fail is the doubling up of the component tags, as bolded. HTML ignores malforrmed expressions and moves on.
"This page doesn't seem to exist."

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