SuperL98

Corvette Fever (May 2009) has an interesting article this month on Aerodynamics.
They took Corvettes, from each generation, and tested them in the AeroDyn wind tunnel (Mooresville, North Carolina).
http://www.a2wt.com

http://i237.photobucket.com/albums/f...8new/aero1.jpg


I don’t think I can “legally” post the whole article, but here are the graph results.
Data seams to be taken at 85 mph, and “Passengers” means they placed weight in the seats.

http://i237.photobucket.com/albums/f...8new/aero2.jpg

http://i237.photobucket.com/albums/f...8new/aero3.jpg


I put their CDA, Lift/Drag Ratio, and % Front Lift, into a spreadsheet and calculated values up to 200 mph.
Just did the base model coupes, with passengers.
Keep in mind this is just Aerodynamic Drag (from the data) and no rolling resistance.

http://i237.photobucket.com/albums/f...8new/aero4.jpg


And front and rear lift, again from their data.

http://i237.photobucket.com/albums/f...8new/aero5.jpg

http://i237.photobucket.com/albums/f...8new/aero6.jpg


Interesting stuff, if the data is believable?
The C5 has the lowest drag.
The C4 & C3 have the lowest rear Lift, even lower than the C6?
Look how high the C4 drag coeff is 0.371 ?

Anyway, hope this is interesting..

63Corvette

Thanks for posting SuperL98. That's a great article. I race a C2 coupe and drive a C5 Z06 as my daily driver (with ocasional track), so I can make a valid comparison. The figures seem to reflect what I see and feel. The C2 is extremely unstable (aerodynamically) due to front end lift at speeds over 150 mph (so are Cobras, but due their design, they can't go much faster than 160). The C5 Z06, on the otherhand, is very comfortable and stable (but loud) at speeds above 150mph.

Solofast

One of the reasons the C4 drag is high is that the sides tuck in between the wheels. The airflow separates after the tires and that causes a lot of drag. Also the footwhells of the C4 are sharp edged and that causes a lot more drag as the airflow leaves the engine compartment. If you look under a C5 you will see how they addressed that and smoothed the flow coming out of the engine compartment.

Note that the drag increment with the headlights up is really high on the C5, compared to the C4 where they smoothed the edges of the headlight surrounds and didn't have an overhanging lip on the front edge like on the C5... The C5z had lower drag with the headlights closed, but opened they were higher.

Also interesting is the impact of the notchback body on the C5Z compared to a coupe. The drag increment isn't all due to the bodywork, the wider front tires are also a good part of it, and one of the reasons that the fat tires were left off of the base C5 is what they did to the CAFE numbers due to the higher drag.

Another interesting comparison is the front end lift on the C5Z compared to a C5 coupe. The differences there are the brake ducts which pump air into the wheel well.... Still, if you are going to Bonneville, it sounds like a C5 coupe is the best weapon, it has the lowest drag product (CDA) of all of the cars...

AU N EGL

very good stuff

BrianCunningham

Very informative

Thanks!

ROBERT@SS

Interestingly, the difference between the FRC and the std coupes was even enough to have different hp@50mph numbers for the data within our dyno software. This value is in place to apply an additional load to simulate wind resistance for all vehicles. These figures, even at 50, is suprising.

63Corvette

I think the Moderator should post this information in the FAQ and stiicky area at the top of the board.

PaintballaXX

Interesting. I would have assumed the c6 to take what the c5 did and further improve. I was surprised to see the cda increase instead of decrease. Then again, comparing night time drag of the c5 and c6 their was a small improvement. Perhaps the increased cda was a trade off for better lift characteristics in the rear. Wish they had their hands on a c6z and/or zr1.

Solofast

Part of it was the changes necessary to meet pedestrian impact standards, which caused the nose to be raised up and reshaped(mae more blunt) so that you don't hurt a pedestrain as badly when you run into theim...

cbernhardt

Any idea as to what year C1 was tested?

Charles

SuperL98

Yes, the early cars are:

C1 is a 62
C2 is a 63 Split Window
C3 is a 70
C4 is a 90 ZR1

AeroDyn has a few picture and a video of a C6 in the tunnel, on their web page.






http://www.youtube.com/watch?v=aduap_AS5j8

SuperL98

RC45

Odd they went to all the trouble and never took a C6 Z06 along.

I would really like to know that the changes to the nose, the rear lip and wide wheels would be worth.

63Corvette

"Yes, the early cars are:
C1 is a 62
C2 is a 63 Split Window"

Well that would certainly explain why the lift and drag figures for the REAR of the car were identical for the C1 and C2 Corvettes;-)

Plasticman

That C1 has rear side view mirrors on both sides. Those were not available (only the driver's side was ever used). Therefore, the drag numbers would be a tad higher with the extra mirror.

Plasticman

Canute

I guess it doesn't take a wind tunnel to tell that the C2 would be a poor performer with respect to lift and drag with that nose. One of the reasons I just bought a cruiser C2. Makes me keep it off of any competitive surface.
It does look cool, though .
Interesting that the C6 came out worse than the C5 and C4 in some instances. I thought the C6's Cd was supposed to be ~.29?

TedDBere

Is aero done with the engine running? Would it make a difference in air flow?

Glennm27

Very cool info. Thanks for posting.

Solofast

The amount of air going into the engine isn't significant, in particular at cruise conditions when the throttle is almost closed...

The fans are electric, so they aren't running when you are moving fast.

BrianCunningham

A moving ground plane would have made a difference.