Audi a6 e tron Cd 0.21

[aerohead]

Originally Posted by Phase

If directing air around the tires makes a big diff, I’m wondering how much of an impact actually lowing a car by an inch could make

From the WS12 Aerodynamic Performance Research Findings, Coventry University, 2012:
'There is an almost universal 'rule of thumb' which states that drag coefficient increases by delta Cd = 0.004 for every 10mm of ride height.'
I'll let you do your own math.

[Vekke]

Drag will lower or increase depending on which way you go in ride height.

If you go lower drag will go lower. up to certain limit like from memory 50mm ground clearance.

I have used 40mm change is 0,01 in drag reduction but that was from some very old tests documents. Here probably your cars aero impacts how big impact the lowering has.

[aerohead]

The following were recorded for this car:
220mm GC = Cd 0.3955
210mm GC = Cd 0.3893
200mm GC = Cd 0.3813
190mm GC= approx. Cd 0.374
180mm GC = Cd 0.367
165mm = Cd 0.357
140mm = Cd 0.340
0mm = Cd 0.300
These data points could be entered onto graph paper, ''dots' connected with drafting tools, then different GC 'interpolations' performed graphically from the 'curve' you created.

[Vekke]

More details are coming out on the audi at linkedin:

"Audi A6 e-tron active Aerodynamics: Part 2

Has a car the same Drag coefficient in every condition?

Of course... NOT!

The A6 e-tron has some active aerodynamics devices, to optimise the drag coefficient.

After the first device here:
https://lnkd.in/dsBxstqS

The second device is the active air suspension.
The car can be lowered by 20mm increasing the range by more than 10km.

The A6 e-tron has three level (Normal, Low, Highway) and the car set them depending on the selected Drive Mode and the car speed.
You can see the actual level under the Audi Drive Select Mode screen.

If Drive Mode = Comfort the car stays all the time on Normal.
Drive Mode = Dynamic the car is always on Low.
Drive Mode = Efficiency the car starts in Normal and goes down while the speed increases.

"

That 20mm lowering brings only more than 10km more range so impact to drag cannot be so huge on drag. I think that mainly comes that aerodynamics around wheels are pretty well designed. or they are playing the impact down as that same 10km was used for grill blocks.

Link to post

In this post some windtunnel video:

[Phase]

So it seems like lowering a Prius from 6 inches to 4 inches should give about 4 extra mpg on the highway five or take based on all the different studies averaged out

[aerohead]

Originally Posted by Phase

So it seems like lowering a Prius from 6 inches to 4 inches should give about 4 extra mpg on the highway five or take based on all the different studies averaged out

Since the Audi A2 showed a 'counterfactual, 'black swan', outlier, 'zero' benefit from lowering, nothing about the Prius 2" drop could be predicted with any certainty.
Testing out on the open road leaves you vulnerable to baseline uncertainties, which don't exist in a wind tunnel, or CFD investigations ( $ 4,000 each ).

[Phase]

Originally Posted by aerohead

Since the Audi A2 showed a 'counterfactual, 'black swan', outlier, 'zero' benefit from lowering, nothing about the Prius 2" drop could be predicted with any certainty.
Testing out on the open road leaves you vulnerable to baseline uncertainties, which don't exist in a wind tunnel, or CFD investigations ( $ 4,000 each ).

well the LE prius is half an inch lower and more aero wheel covers and toyota officially says it has a lower drag coefficient.

no idea how much of an improvement comes from lowering another few inches, but at least you can use the superficial excuse of lowering it gives a better sporty look and handling and feel is improved on curvy roads