Dirt Late Model in Wind Tunnel - Dirt Late Model Breaks Wind - Ultimate Racing

Written by on August 1, 2009 What Can Really Be Learned From Testing A Dirt Late Model In The Wind Tunnel? In Short--A Lot!
Dirt Late Model in Wind Tunnel - Dirt Late Model Breaks Wind - Ultimate Racing View All 16 Photos
Ctrp 0908 01 Z+dirt Late Model+in Wind Tunnel 2/16 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.


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!


Ctrp 0908 02 Z+dirt Late Model+observed 3/16 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.


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.



Ctrp 0908 04 Z+dirt Late Model+a2wt 7/16 Dave Salazar from A2WT is getting ready to run the first baseline, this will provide a way of looking back and seeing how much downforce we've gained or lost from our adjustments.

The next thing to do was to put the car at race attitude because, as I'm sure a lot of you readers have already concluded, a Dirt Late Model will never sit that flush when traveling near 100 miles an hour. The guys of Menscer Motorsports were ready and after a few adjustments the car was almost hiking the LF inside the wind tunnel.



Another interesting fact that we came across was how much horsepower we would need just to overcome the drag being produced. Remember from earlier, as the speed increases, so will the drag. We'll need roughly eight times the amount of horsepower to overcome that drag. What we found out was that to achieve a top speed of 135 mph, we would need roughly 400 horsepower. "This is a huge number for you guys," says Salazar. "Now we know that we don't need to be concerned with reducing the amount of drag." This is because no matter how much downforce we create we'll always have an abundance of horsepower to be able to overcome that drag."

This could be a factor for you crate Late Model guys though, if you're only pushing near 400 hp. Then, you might want to look at getting the body as low to the ground as possible and reducing the amount of drag.

Ctrp 0908 06 Z+dirt Late Model+at Attitude 8/16 Putting the car at attitude shows the type of downforce we are creating when the left front wheel is almost off the ground.

Next we reduced the speed of the wind to 40 mph and were able to see how the air was traveling around the car by doing a smoke-wand test. We don't record any data during this test but we were able to see exactly how the air travels over the body. What we were able to determine and see was where the "dirty air" was being produced. We could see that the air traveling across the center of the hood wouldn't actually ever get to the spoiler, but the air flowing over the right and left sides of the spoiler is where all of the downforce was made.



Rear Spoiler Now, the rear spoiler is where we found some really good information. A small rear spoiler change can affect how the car handles drastically. A good example of this is the gurney bracket that was attached to the rear spoiler. The flap is only a couple inches wide and it helps hold as much rear downforce as possible. What we did was take the gurney flap and turn it around backwards to where it faced the direction of the wind just to see if we lost downforce. We found that we lost 100 pounds of downforce at the rear of the car. Someone asked, "Is that a big change?" To which Dave responded, "Well if your driver can't feel 100 pounds of change, you need a new driver."

Ctrp 0908 11 Z+dirt Late Model+smoke Wand Test 12/16 The smoke-wand test allows us to see how the air was traveling over the car.Notice once the wind gets to the air filter cover, it splits toward the passenger-side of the vehicle--providing a more direct hit on the spoiler. This is why we saw an increase in the rear downforce with this piece.


At first we thought the bolt wasn't tightened and that the rear spoiler had slid back to its original height, but we noticed we still had recorded an increase in drag. The team found the stall point of its rear spoiler. This goes back to what we'd talked about before--increasing drag will not necessarily increase downforce. Even though the spoiler was causing more drag for the entire car, it wasn't increasing the downforce for the rear of the vehicle.

Ctrp 0908 12 Z+dirt Late Model+down Force Data 13/16 Now with all the downforce numbers that Menscer Motorsports has, it will know how big of an adjustment it's making when it tilts the rear spoiler, or if the team attaches a new roof. This is why time in the wind tunnel is beneficial.





A2 Wind Tunnel
Mooresville, NC 28115

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