There really can be a lot...
There really can be a lot learned from spending some time in the wind tunnel. We were lucky enough to be able to tag along with Menscer Motorsports when it visited the A2 Wind Tunnel in Mooresville, N.C.
I know what you're thinking, Come on, a Dirt Late Model in the wind tunnel. . .are you serious? But before you start blasting us for having Cup envy (a term where race teams do things just because they see NASCAR Sprint Cup teams doing them), take a moment and put down your pitchforks and torches, and have a read about what we learned from tagging along with a Dirt Late Model team on its trip to the wind tunnel.
To better understand the data we learned from having a Dirt Late Model in the wind tunnel, you need to have a crash course in aerodynamics, and understand a few terms that we'll be mentioning throughout the article.
Dave Salazar from the A2 Wind Tunnel defines aerodynamic drag as a force in the opposite direction of the vehicle's forward movement. Drag will increase as the speed of the vehicle increases. You need enough power to move the air around the vehicle, and at low speeds drag isn't too much of a concern. However, as the speed increases, so will the aerodynamic drag on the vehicle. It will increase by approximately the square of the speed increase. What that means is, if you double the speed of the vehicle, you will increase the drag forces on the vehicle by about four times!
So, imagine that your drag force is 70 pounds at 50 mph. Then the drag force at 100mph would be close to 280 pounds. What makes this important is that the horsepower required to overcome drag is dependent on the speed as well. HP=Drag Force x Velocity. This means as the speed increases, the horsepower required is now approximately the cube of the percent of the increase in speed. Every time the speed doubles, the horsepower required to overcome the drag forces is increased by about eight times!
The guys at Menscer Motorsports...
The guys at Menscer Motorsports were ready for the tunnel, they brought adjustable tie rods that allowed them to put their car at ride heights as well as different hoods, spoilers, fenders, and more.
A byproduct of the development of downforce is drag. However, the two don't necessarily correlate with changes in magnitude. You'll see a perfect example of this later with the rear spoiler on the Dirt Late Model. You see, the aerodynamics of the Dirt Late Model body, or any racing body for that matter, are extremely dependent on every factor of that body. What I mean is this, if I change a rear spoiler to gain rear downforce, I could increase or decrease the front downforce because the air-flow across the front of the car is affected by the new rear spoiler angle. In essence, the airflow across every part of the car can be influenced by changes to any part of the car. This is specifically where wind tunnel testing could benefit teams.
The guys at A2 Wind Tunnel (A2WT) were gracious enough to let us tag along when Menscer Motorsports brought its Dirt Late Model into the wind tunnel. The numbers that were recorded really caught us by surprise. Out of respect for Menscer Motorsports, I won't be able to share all of the downforce numbers, but I will be able to show where we saw gains and where we didn't.
The key to having a successful test at the A2WT is to be prepared and the guys from Menscer Motorsports were. They had pulled the shocks off the car and put the car at normal ride heights using adjustable length rods. This meant that the car would not change its ride or pitch attitude as a result of the 85mph wind that it was going to feel. We could run our tests over and over again without having the numbers being skewed by changes in the car's attitude.
Once we strapped the car down and centered it, we were ready for our first run. The baseline run would show us our first downforce numbers for the front and rear of the car, along with side forces and drag. The results came back and what amazed us more than anything was that almost 70 percent of the downforce was being made at the rear of the car. When compared to a sleek Sprint Cup car, the Dirt Late Model produces a ton more drag, however the downforce numbers are much higher than a Cup car.
We had to square the car inside...
We had to square the car inside of the tunnel, since it would be strapped to a set of monitors that would feed the A2WT computers with all of the data collected.