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I hadn't seen this posted yet, and got a response from the Corvette Concierge, who says HE got it from the Engineers.
Base car, 0.32
Z51, 0.39
Which might explain the big difference in top speed, and the base catching up to the Z51 on the drag strip.
EDIT TO UPDATE: As I was rolling lucky and they were actually answering questions, I took a shot at lift coefficients, frontal area and pitch moments. They passed on that, saying "they do not publish at this level of detail". BUT, he added, they said the Z51 maxes out at 400 lbs of downforce, and the base is "about neutral". So likely just a touch of lift. As opposed to the base C6, which had HUGE lift in the nose. And I believe I saw a Tadge comment on here about how serious they are about pitch moments, making sure the load is balanced front to back. Again, the C6 most definitely was not.
Just sharin'.
Last edited by godzilladude; Nov 15, 2019 at 09:21 AM.
I hadn't seen this posted yet, and got a response from the Corvette Concierge, who says HE got it from the Engineers.
Base car, 0.32
Z51, 0.39
Which might explain the big difference in top speed, and the base catching up to the Z51 on the drag strip.
Just sharin'.
I forget which video it was but on one of the many circulating during the reveal period, an Engineer stated the High Wing reduced drag and increased downforce...I took it he meant over the base and the Z51 but as I remember his words it wasn't entirely clear, but assuming he was talking Z51, at minimum the high wing will help out with high speed runs vs. the Z51.
Last edited by usrodeo4; Nov 10, 2019 at 03:53 PM.
As someone that plans on using this car for texas mile, air strip attack and silver state classic events, I'm planning on starting with the base. Nice to hear the DC is as low as a .32 Considering the Chiron has a reported .36, it should be an excellent top speed platform.
Tadge answered: The standard Stingray has a drag coefficient of .30. Its frontal area is 2.02 square meters and has a lift coefficient of .20. Generally speaking, as you move up the Corvette model range, frontal area and drag go up and lift goes down. This is not just true of Corvette, but virtually all performance car lines. Frontal area goes up because tires get wider and you have more aggressive aerodynamic features. The aerodynamic aids that create downforce tend to disturb the air in such a way as to add drag. Directing air through heat exchangers and towards brakes to cool them also creates drag. As engines make more power, more energy needs to be dissipated in all cooling systems including coolant, oil, trans and differential lube, and in the case of charged engines, intake air.
Race cars have a lot of drag by street car standards, but they produce a lot of downforce. Race teams spend a lot of time optimizing this tradeoff for a given track. They also have to make sure the drivers like the way the car handles. It is no different for street cars, we are always looking for ways to improve down force at the minimum drag penalty. The Z51 option on the Stingray adds cooling content, a rear spoiler and modifies the aero panels under the nose of the car. It's Cdx moves up to .35 but lift drops to .03, which is very close to a zero lift car. Actually, we have tested Z51 cars with negative lift coefficients, which means those cars are producing true downforce.
The Z06, with its wider tires and flared body panels has a higher frontal area (up to about 2.1 square meters) and the standard car has drag and lift numbers similar to the Z51. The Z06 has available Stage 2 (CFZ or CFV Carbon Fiber Ground Effects) and Stage 3 (Z07 Performance package with the large end plate on splitter and the center bridge "wicker" on the rear spoiler) aero packages that further trade drag for additional downforce. Stage 2 has a "lift" coefficient of -.152 and stage 3 is -.279. The minus signs mean negative lift or down force. The trade off in drag means those coefficients move from about .40 to .50. In other words, the cars are starting to approach race car numbers. In our testing on many tracks, the improvement in corner speeds more than offsets the straight line speed loss from the higher drag. Depending on body style, our aero packages have lift to drag ratios ranging from 2.6 to 3.6. We consider anything over 2.0 (2 counts of lift reduction at the cost of a single count of drag) an efficient tradeoff.
You asked about front to rear down force ratios or what we call "Pitch moment". We have strict criteria for pitch moment. The ratio needs to be held within a fairly narrow range so that the vehicle handling remains consistent. Too much down force on the rear and the car will understeer at higher speeds. Too much on the front and the car will oversteer. We tune all our cars to maintain neutral handling biased slightly towards understeer.
I am sharing these specifics with you quite reluctantly. The reason is that there are many ways aero performance can be quantified. No two wind tunnels are exactly the same. Some have moving ground planes, some do not. Many correction factors are used because none of them replicates exactly what happens in the real world. They have finite test spaces while the world is far more open. Computation fluid dynamics (CFD) is getting so good, it is used widely and surpasses physical testing in some ways. Bottom line is that with so many ways to predict them, numbers from one manufacturer are only roughly comparable to another. In addition to the number of ways to measure, the cars themselves can be variable. Small changes in standing height or pitch (relative height of the front to the rear) can have a big effect on measured numbers. Thank you for the question. I have tried to keep the answer to a level everyone can understand. Aerodynamics can very quickly become a complex technical discussion.
Great info. Interesting that Tadge states that anything over 2:1 lift:drag is good. APR wing CFD shows about 8.8:1 at low angle of attack. Although that number is probably inflated the 2:1 is still a parachute in comparison.
I wonder what the C8 high wing ratio is?
Great info. Interesting that Tadge states that anything over 2:1 lift:drag is good. APR wing CFD shows about 8.8:1 at low angle of attack. Although that number is probably inflated the 2:1 is still a parachute in comparison.
I wonder what the C8 high wing ratio is?
I really hope c8 Z06 has a proper wing option. Not a permanent air brake. C7 Z07 has a drag coefficient similar to a G Wagon or Jeep Wrangler. No matter what Tadge says, this isn't an efficient Downforce/drag ratio at 0.50 Cd for some 500 lbs of downforce at top speed.
Last edited by BrunoTheMellow; Nov 12, 2019 at 01:35 PM.
The wing option on the C8 Z51 is a very good sign. Move it back and make it bigger and we’re set.
Let's put things into perspective:
Viper ACR makes 1700 lbs of downforce at 177 mph with a Cd of 0.54.
viper TA makes 460 lbs at 150 (probably close to 600 at 185) with a Cd of 0.37
C7 Z07 makes ~500-600 lbs of downforce at top speed (185) with a Cd of "about 0.50".
Gt3RS makes 770 lbs at 186 mph with a Cd of 0.33 (basically Cd of z51 model).
Price aside, this is pretty significant drag for the Z06.
Last edited by BrunoTheMellow; Nov 12, 2019 at 02:49 PM.
Street car with some cheap aero added vs track cars. At least the C7Z and GS have some. Stock C6Z basically had none so it’s a step in the right direction. Hope the C8Z and GS go a step further.
I hadn't seen this posted yet, and got a response from the Corvette Concierge, who says HE got it from the Engineers.
Base car, 0.32
Z51, 0.39
Which might explain the big difference in top speed, and the base catching up to the Z51 on the drag strip.
EDIT TO UPDATE: As I was rolling lucky and they were actually answering questions, I took a shot at lift coefficients, frontal area and pitch moments. They passed on that, saying "they do not publish at this level of detail". BUT, he added, they said the Z51 maxes out at 400 lbs of downforce, and the base is "about neutral". So likely just a touch of lift. As opposed to the base C6, which had HUGE lift in the nose. And I believe I saw a Tadge comment on here about how serious they are about pitch moments, making sure the load is balanced front to back. Again, the C6 most definitely was not.
Just sharin'.
Hence the fender louvers and hood outlet. Fenders also extracted engine bay high pressure air. The hood outlet and front splitter caused downforce which balanced the rear wing and diffuser downforce. I also have louvers on my front fenders. My C6Z has perfect mechanical and aero balance with my functional diffuser and APR wing
Hence the fender louvers and hood outlet. Fenders also extracted engine bay high pressure air. The hood outlet and front splitter caused downforce which balanced the rear wing and diffuser downforce. I also have louvers on my front fenders. My C6Z has perfect mechanical and aero balance with my functional diffuser and APR wing
Let's put things into perspective:
Viper ACR makes 1700 lbs of downforce at 177 mph with a Cd of 0.54.
viper TA makes 460 lbs at 150 (probably close to 600 at 185) with a Cd of 0.37
C7 Z07 makes ~500-600 lbs of downforce at top speed (185) with a Cd of "about 0.50".
Gt3RS makes 770 lbs at 186 mph with a Cd of 0.33 (basically Cd of z51 model).
Price aside, this is pretty significant drag for the Z06.
Add to that list the 991 GT2RS, with ~992lbs of downforce at top speed (211) with a Cd of 0.35. They've done a phenomenal job on the aero on their cars.
I hadn't seen this posted yet, and got a response from the Corvette Concierge, who says HE got it from the Engineers.
Base car, 0.32
Z51, 0.39
Which might explain the big difference in top speed, and the base catching up to the Z51 on the drag strip.
EDIT TO UPDATE: As I was rolling lucky and they were actually answering questions, I took a shot at lift coefficients, frontal area and pitch moments. They passed on that, saying "they do not publish at this level of detail". BUT, he added, they said the Z51 maxes out at 400 lbs of downforce, and the base is "about neutral". So likely just a touch of lift. As opposed to the base C6, which had HUGE lift in the nose. And I believe I saw a Tadge comment on here about how serious they are about pitch moments, making sure the load is balanced front to back. Again, the C6 most definitely was not.
Just sharin'.
Added your info to table I have in my C7 Aero PDF. Fits. That data came from comments Tadge made in several forum posts and video.
Read somewhere that the C8 high wing added about the same high downforce as the low standard Z51 Wing. I have the Stage 2 Aero on my C7 Grand Sport and ordered the Ground Effects for my C8 so interested in that data . Will keep and eye out for other and reinforcing data.
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Drag coefficients
Added your info to table I have in my C7 Aero PDF. Fits. That data came from comments Tadge made in several forum posts and video.