Instead of being adjustable...
Instead of being adjustable for angle, most Sprint Car wings are adjustable for fore and aft location. This adjuster moves the wing back and to a slightly higher angle. The idea is to move the center of force rearward as the track changes toward slick conditions. It might be of more use to cause a change of angle adjustment. High angles could be used for dry and slick conditions to promote high drag and cause more load transfer to the rear for more bite. Lower angles that are more efficient for downforce could be employed on tighter tracks for more overall traction. This is something that has not been considered before, but it is something you might think about.
I raced non-winged Sprint Cars and entered some WoO events without a wing. The car was radically different, and had four-wheel independent suspension. I built a hood that gave quite a bit of downforce with minimal drag. It wasn't as fast as a winged car, but it wasn't as different as you may think. I am not saying a Sprint Car shouldn't have wings. I am trying to show you that what the wings are doing is probably not what you think they are doing. My opinion is the racing is better without them.
As with most aeronautical problems, with both race cars and airplanes, there is a whole lot more going on than initially meets the eye. The more you evaluate the problem, the more difficult the problem gets. In this case, a flat sheet of metal or a piece of plywood would work about the same as the wings on a Sprint Car. So, why go to the trouble of having a bottom surface of the wing other than for structural reasons?
Wind Tunnel Errors and Why
Wind tunnels will not accurately tell us how our wings are working. That is because the air in a wind tunnel is charged with energy from the simple fact that it is in motion and the walls and the ceiling are too close to the car. In most wind tunnels, the air is moving in excess of 60 mph. This means that the air possesses energy and air in motion will desire to stay in motion greatly affecting its physical movement as it flows around the car and wings.
In contrast to the Sprint...
In contrast to the Sprint Car wing, the wings on most other types of race cars including this Grand Am Daytona Prototype car, are set high off the body and at a relatively low angle, around 10 to 14 degrees. It is known that an angle of attack greater than 16 degrees on these cars will produce a stall and high drag numbers. Compare that to a Sprint Car wing that is set at 25 to 35 degrees of angle.
In contrast, when we drive a Sprint Car into still air, that air has little or no energy. It is able to be pushed aside more easily and can move more quickly to fill the vacuum created behind objects such as the wings and the car itself.
It is this vast difference in the dynamics of still air verses moving air that causes errors in the evaluations in a wind tunnel. A more accurate way of evaluating your wings would be to do on-track testing utilizing the yarn tuft method I previously talked about and observe using a video recording.
Conclusion
Think about how your wing works and how you drive your Sprint Car. Top teams may have an edge here and have already re-evaluated their wing angles and driving attitudes. Watch the top teams as they race. If they crank angle out of the wings, they might just be looking for more, not less, downforce for tacky track conditions.
Higher wing angles might provide the needed bite on dry and slick tracks from more drag induced load transfer to the rear and that provides more acceleration that may be needed over top speed. With all of this new knowledge, you might need to re-evaluate your strategies concerning wing angles and placement. I hope so.
The sideboards on a Sprint...
The sideboards on a Sprint Car wing can obstruct the oncoming air when the car is traveling at an angle to the direction of travel. This sideways slide reduces the efficiency of the wing and also moves the center of force forward. Attempts are made to reduce this effect by lowering the right side panel, but it still sticks up 4-6 inches or more. That is enough to disturb the airflow and reduce what little downforce exists. This chart shows the area that is affected by the sideboard. Remember that both sides of the wing are affected by the board, so lowering the right side board only helps with the "flat panel' downforce, not wing-induced downforce because the underside is important also and is highly obstructed by the side panel.
This car is running at approximately...
This car is running at approximately a 20 degree angle, so the obstruction chart applies to this attitude. Granted, this is not an extreme angle of slide for a Sprint Car, but enough to matter. Imagine a car sliding at a 45 degree angle and what that would do to the wing efficiency. The more straight ahead you can run, the more efficient the wing will be.
The most useful aero testing...
The most useful aero testing is done on-track. Because we drive through still air as opposed to moving air flowing over our cars, wind tunnels might not tell us all there is to know about aero efficiency. Moving air has energy whereas still air does not. That makes a huge difference in how the air reacts to the surfaces on our race cars. Here, we see pre-prepared lines of yarn strips attached to a car for evaluation. On our Sprint Car, we could attach these onto the wing and body panels and take video using a GoPro camera or similar video source to see how the air is flowing over those surfaces. We could learn a lot about how everything works aero wise.