Car & Driver Aerodynamics Test

[UltArc]

I don't know about that Cd of the Insight, if they got one off the road, I am guessing it is missing chunks. Most G1s are missing underbodies, wheel skirts, every one I have seen has destroyed tire spats/wheel wells.

The thing that still keeps it ahead is the FA. Even a better CD Prius will have a worse CDa with how giant (in comparison) it is. Same concept of the Elio, as it has poor CD but a tiny FA.

[Thenorm]

Originally Posted by California98Civic

That CLA number looked bogus from the beginning. Nice to see a test of it. .30 instead of .23! I wonder how much could be innocent variation between testing facilities? Any of it?

the quoted 0.23 is for the special bluemotion edition in europe with extra features such a narrow LRR tires, grill shutters, etc.

[Cd]

This isn't the same test is it ? ( Note the color of the car and the wheels )

[Cd]

So why not email the guys at the A2 and ask about what condition the Insight G1 was in ? Or as i have mentioned in the past, ask if they would join us for a VIP Q&A session ?

( I think you forum moderators would have more clout than I would .)

117 Godspeed Ln, Mooresville, NC 28115

(704) 799-1001

A2 Wind Tunnel

[aerohead]

Originally Posted by Frank Lee

More proof we shouldn't get too hung up on small published Cd variations; who knows if they're accurate anyway?

I'm not current on this sort of thing,but in Hucho's first English translation book of the mid-80s he reported that a VW 1600 was taken to all the pertinent wind tunnels and measured.There was no agreement between any of the tunnels,but their was a standard deviation of around 2.5% or so,and many tunnels' Cds were within this standard deviation.
The GM,Lockheed Marietta,Pininfarina,and one other tunnel in Europe had the 'best' results.
There exists a standard wind tunnel calibration model which all tunnels are supposed to use.
I suppose that its a GOOD thing that automakers think Cds are important enough to 'fudge.'

[RobertISaar]

2.5% is a pretty tight deviation considering the published and measured values being stated here.

[aerohead]

Originally Posted by Old Tele man

I'm more inclined to think the "differences" could be the result of 'static' (no tires rotation) versus 'dynamic' (dynamometer) wind tunnel testing techiques. Spinning wheels create eddy currents which create a LOT of drag!

One SAE Paper from General Motors in the 1960s reported that the difference in Cd between spinning and stationary wheels was of such a low statistical significance that it didn't warrant the time and expense to test; and spinning tire effects could be easily simulated with trip strips in the tire/wheel area.
Exposed-wheel race cars MUST be tested with spinning wheels.

[aerohead]

Originally Posted by Old Tele man

The *information* that I thought MOST USEFUL was their listing of aero power at 70 & 100 MPH:

14 HP @ 70 MPH; 42 HP @ 100 MPH - Tesla S P85
14 HP @ 70 MPH; 42 HP @ 100 MPH - Toyota Prius (GenIII)
16 HP @ 70 MPH; 45 HP @ 100 MPH - Chevrolet Volt
16 HP @ 70 MPH; 48 HP @ 100 MPH - Mercedes-Benz CLA-250
18 HP @ 70 MPH; 53 HP @ 100 MPH - Nissan Leaf SL

...that's two KNOWN points on their respective aero curves!

Their was a time when Csaba Csere (MIT graduate engineer) was the Technical Director at CAR and DRIVER and he made sure that at least some of the road tests included Road Horsepower figures based upon coastdown testing at the Chrysler Proving Grounds,just a stones toss from Hogback Road where C&D had their offices.
I was so impressed by this capability that I arranged to have the CRX fee-tested by them in 1991.
I'm delighted to see the article,and that Don Sherman is still beating the aerodynamic drum.It was his "CRISIS FIGHTER PINTO" article in May,1974 which got me into streamlining.

[aerohead]

Originally Posted by Cd

This isn't the same test is it ? ( Note the color of the car and the wheels )

The curved test section walls and overhead lighting are identical to those in the C&D photos.A2 is a good guess!

[aerohead]

Originally Posted by RobertISaar

2.5% is a pretty tight deviation considering the published and measured values being stated here.

If we could duplicate the test at different tunnels we'd have our answer.