Why Cd vary so much within same models of car?

[AEOLUS]

Originally Posted by Phase

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…

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

[Phase]

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?

[AEOLUS]

Originally Posted by Phase

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..
?

[Hersbird]

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?

[freebeard]

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

[aerohead]

Originally Posted by AEOLUS

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?

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.

[aerohead]

http://https://ecomodder.com/forum/s...0-a-24646.html

Originally Posted by Phase

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…

I 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.

[IRONICK]

Originally Posted by aerohead

http://https://ecomodder.com/forum/s...0-a-24646.html

I don't believe that KIA/ Hyundai / Genesis reports complete drag coefficients

Yeah, sure. Only Ford reports correctly.

[AEOLUS]

Originally Posted by aerohead

http://https://ecomodder.com/forum/s...0-a-24646.html

I 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.

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


cla

[aerohead]

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.