new mercedes b class 0.24 Cd

[Cd]

It looks as if the Golf has pretty much the exact same roofline slope as the B class. ( Yet is stuck at .31 Cd )

[aerohead]

Originally Posted by Cd

It looks as if the Golf has pretty much the exact same roofline slope as the B class. ( Yet is stuck at .31 Cd )

If the max camber point on the M-B was 'forward' of that for the VW,it would have undergone a bit more pressure recovery and it's base pressure would reflect in the lower Cd.Just thinking out loud.

[Cd]

Originally Posted by aerohead

If the max camber point on the M-B was 'forward' of that for the VW,it would have undergone a bit more pressure recovery and it's base pressure would reflect in the lower Cd.Just thinking out loud.

Thanks Phil !

I can't detect a difference except that the MB has a longer roofline which extends out farther at the back.

The MB also has a slightly flatter windshield than the VW, so the VW actually seems to match the template even more closely towards the front of the car.

I don't trust my sloppy overlay though. I think some of what i am seeing is the smoke stream.

The point of all of this being to show just how closely that cars match the MB , yet the VW is a full 7 counts higher.

[aerohead]

Originally Posted by Cd

Thanks Phil !

I can't detect a difference except that the MB has a longer roofline which extends out farther at the back.

The MB also has a slightly flatter windshield than the VW, so the VW actually seems to match the template even more closely towards the front of the car.

I don't trust my sloppy overlay though. I think some of what i am seeing is the smoke stream.

The point of all of this being to show just how closely that cars match the MB , yet the VW is a full 7 counts higher.

If they would provide us with accurate plan view photos shot from above,we'd have a fair chance to better sort all this out.Thanks for images! Posting these things are my greatest challenge.

[ChazInMT]

Hey Cd,

I drawed outlines on both a them there autobahnstormers, the VW Golf and MB B, and superimposed the outlines. I was very careful to not distort them, so I'm confident these template images are within 1/4" of the real cars thus representing true shapes.

In order to "Line them up" I had to choose between matching length, or matching height, I chose Height and I matched windscreen tops/ fronts of roofs. It just showed all the difference best.



4 things I notice.
1) The VW is Green and MB Red.
2) The hood area has a dramatic difference.
3) The bottom rear diffuser area is really different.
4) The MB has a few more inches of drop in its roof line and the peaks of the roofs are 12-18 inches apart. When I slid the MB back to try and match roof peaks, something interesting happened as well, the roof lines matched up. So indeed, MB has their roof peaking earlier.

So from the perspective of the roof peaks, the Golf has a lot more sticking out in front, and the MB has more sticking out the back, Hmmmmm.




Hope this helps.

[Cd]

Thanks Chaz. You rock.
I believe the 92-95 Civic hatch has the same problem as the golf - the roofline does not slope down enough at the tail end of the car.

[Rokeby]

From the link posted by Fabio:

"A whole range of measures were necessary in order to attain the excellent
drag coefficient," explains Dr Teddy Woll, Daimler's head of aerodynamics at
Daimler AG. "Apart from an aerodynamically efficient basic design, these
include numerous optimisation measures on points of detail, such as the air
flow around the front wheels, the underbody design and the flow of cooling
air."

The aerodynamics of the 2012 B-class were optimised using complex
computer calculations and flow simulations which required more than 275,000
CPU hours. Models and prototypes spent around 1100 hours in the wind
tunnel.

I take it this means it will be difficult to duplicate/transfer the subtle
aerodynamic "optimisations" with Coroplast, duct tape and a box cutter.

[autogyro]

It takes a whole lotta megaWatts to gain a few kiloWatts

[Cd]

Originally Posted by Rokeby

From the link posted by Fabio:

"A whole range of measures were necessary in order to attain the excellent
drag coefficient," explains Dr Teddy Woll, Daimler's head of aerodynamics at
Daimler AG. "Apart from an aerodynamically efficient basic design, these
include numerous optimisation measures on points of detail, such as the air
flow around the front wheels, the underbody design and the flow of cooling
air."

The aerodynamics of the 2012 B-class were optimised using complex
computer calculations and flow simulations which required more than 275,000
CPU hours. Models and prototypes spent around 1100 hours in the wind
tunnel.

I take it this means it will be difficult to duplicate/transfer the subtle
aerodynamic "optimisations" with Coroplast, duct tape and a box cutter.

That is what I have always been led to believe ...until I saw what AndrewJ did with his box cutter and some junk plastic sheeting. ( Even before the boat-tail )
He dropped his Cd from .31 down to .26 with just a few mods.
Also, i think back on the Hot Rod 'project red hat' Camaro. They did some wind tunnel testing on the car yes - but not thousands ( or even hundreds ) of hours in the wind tunnel. They got a pretty much stock looking '80 Camaro down to .20

Car Aerodynamics - Hot Rod Magazine

[tjts1]

Why is this news? The E class coupe had a 0.24 CD 2 years ago. MB's stated goal is less than 0.20 by 2015.