Sprint Cars are the model of simplicity. Straight front axles, open wheels and cockpit, and minimum weight often make for lots of fun, and some really intense racing. But one area where Sprint Cars haven't been given as much attention as their Stock Car brothers is in the area of aerodynamics. Yes, Winged Sprint Cars have those huge wings to provide plenty of downforce, but what about the "naked" cars? That's why when Dave Salazar, general manager of the A2 Wind Tunnel, told us about a Midget team coming to test, it definitely got our interest.
The race team is Brown & Miller Motorsports, which races USAC-sanctioned Midgets. "We really just went there the first time wanting to figure out where we were aerodynamically," says Brad Noffsinger, who manages the team. "But we really learned a lot, specifically about how air moves through the radiator-and not just getting a lot of air to the radiator. It turned out that exhausting the air out of the radiator and the engine compartment was a big issue with cooling. We did a few panel adjustments and added a few NACA ducts to move more air and it cooled the water temps 25 degrees on the racetrack. Once we learned that, we could go back to hopping up the motors and making more power."
With all of its exposed suspension...
With all of its exposed suspension and framework, you wouldn't at first think that there is much that can be gained from testing a Midget race car in a wind tunnel. As we've learned, that thinking is wrong.
To keep prices affordable...
To keep prices affordable for Saturday-night level race teams, A2 Wind Tunnel does not have a mechanism for spinning the wheels like its larger Aerodyne brother. Instead, Salazar has developed a system that calculates the turbulence created by a "trip strip" taped to the tires 22 degrees behind vertical. The math working behind the scenes is a mad science, but the solution is accurate, effective, and best of all for racers on a budget, economical.
Here's a look at a baseline...
Here's a look at a baseline run for the car. If a customer wishes, A2's staff can blow smoke over the car to help the race team to "see" how air moves around the car, although this isn't necessary for gathering data. Notice here how all the air coming off the hood is essentially directed right into the driver's helmet.
Noffsinger hit on an area where Salazar stresses smart race teams can capitalize on during wind tunnel testing even if the rules on bodies and aerodynamics are very restrictive. In essence, a wind tunnel can tell you a lot more about how airflow is affecting the race car beyond downforce and drag (although both are important).
"If you take the time to look at pressure differentials, you can really do a lot of interesting things inside a wind tunnel," Salazar says. "So even though the Midget doesn't have any fenders you can move around, or even a wing like one of the Winged Sprints, there was a lot this team could do.
"Besides looking at different ways to get more air through the radiator, we also tried two different hoods. The hood shape is not only important for the obvious aero issues, but they also had different scoop designs and by putting monitors inside the air cleaner, we were able to see which design got more air to the engine's intake.
"So even though one hood may look sleeker on the car, if it is choking off the air available to the engine it could actually be costing you speed on the racetrack. And there's really no way to tell without some form of testing."
Noffsinger adds, "We also looked at ways to keep the air from buffeting the driver's head so much on big race tracks. That's something he won't notice until it goes away, but it will help concentration. But the interesting thing about that are the changes that we made I think also made the car safer. We moved some panels around and rounded the edges on them to get the air to track a different way. And getting rid of any sharp edges near the driver is always a good idea, so it is a benefit two different ways."
One of the primary goals of...
One of the primary goals of the Brown & Miller Motorsports team's test was to find ways to maximize air going through the radiator. After getting a baseline, one of the first changes was to install an aluminum shroud around the radiator which will essentially seal off the gap between the radiator and the hood. By using pressure sensors, A2 can tell how much this changes airflow. The result is an 11 percent gain in air moving through the radiator core-the cooling equivalent of moving 2.8 mph faster at the 140 mph baseline.
The team also tried taping...
The team also tried taping up all the holes created by the front suspension. The exposed suspension is a dirty area aerodynamically on any Sprint Car, and this change did cut drag by 1.4 horsepower (in other words that's a 1.4 hp savings), but no changes have been made on this yet. Noffsinger says this will be a factor as the team designs a car in the future.
After realizing that the visor...
After realizing that the visor in front of the cockpit doesn't do much to keep air off the driver, the team tried a run without it. Removing the visor however may not be a good idea. It only creates 1.7 horsepower in drag but is worth 13.5 pounds of downforce at 140 mph.
Here's another very interesting...
Here's another very interesting test. The older-style hood looks a lot dirtier aerodynamically, and it is. Compared to the smoother orange hood in the previous photos, it requires an extra 5.7 horsepower to push the car to 140 mph, but-and this is a big but-it pushed 13 percent more air through the air cleaner and into the engine. Now that the team has this information, it will use a track test to determine if the extra air to the engine can overcome the aerodynamic drag. In the future, however, you can probably expect Brown & Miller Motorsports to develop a hood that melds the best aspects of the two together.
One area that almost all non-Winged...
One area that almost all non-Winged Sprint Cars struggle with is creating rear downforce. As you can see here, the exposed driver's seat creates a large area of low pressure. The low pressure area is strong enough to actually suck smoke from the wand against the flow of air through the tunnel where it pools behind the driver's headrest. This low pressure area creates lift on the racetrack.
Look how the smoke is directed...
Look how the smoke is directed directly at the driver's head. And the turbulence you can see in the smoke after it strikes the driver's helmet means that the driver is experiencing a lot of buffeting. Noffsinger says future efforts will be made to keep the air off the driver to give him a more stable driving environment to help improve his ability to pilot the race car.