06. The deck on a dirt car...
06. The deck on a dirt car isn’t just to keep mud away from the chassis. It actually creates downforce along the length of the chassis. The spoiler creates a high-pressure zone of air that extends from the spoiler forward. By keeping the deck smooth and free of splits, cracks and holes it helps that high-pressure zone to work more efficiently and creates a large area of downforce.
When we talked to Strickler, before he would even begin talking about aerodynamics he stressed the need for maintaining proper balance. “Sometimes it is possible to overload either the front or the rear of the car when it comes to aerodynamic downforce, depending on what the rules allow,” Strickler explains. “If you cannot get the grip between the tires and the track balanced from front to rear, you can be better off by backing off on the downforce generated to get the car back into balance so that you aren’t always too loose or too tight. It can be tough to give it up sometimes, but I’ve seen how it can make you faster.”
As an example, Strickler points to a weekend racing at County Line Raceway in North Carolina. County Line allows its Modified classes to run an 8-inch tall rear spoiler. After struggling through the hot laps session to find the right balance for the car, Strickler says he eventually realized the tall spoiler was simply too much for the Modified chassis given the racetrack and conditions. At the last minute his crew bolted up a smaller 5-inch spoiler and proceeded to set the track record.
The moral here? Easy: When it comes to racing the only thing that matters is how quickly you can get around the track. Take advantage of everything you can—aero, chassis, engine, you name it—but if anything gets in the way of lowering your lap times, ditch it like a bad habit.
Yes, there is such a thing as aerodynamics for dirt cars. here’s how to take advantage of it.
Aerodynamics play a larger role on how your race car behaves the faster you are going, but even on tight, low-speed racetracks taking advantage of a few aero tricks can help you gain an advantage on the competition.
07. The air moving past the...
07. The air moving past the driver and the cockpit is incredibly dirty. You can help clean it back up and guide the air back to the spoiler by building a “bullet” behind the driver seat. But a sheetmetal bullet like this also serves a second purpose. Air that falls into the driver’s compartment is no longer on the deck creating downforce. The bullet can actually help divert that high-pressure air away from the driver’s compartment and back onto the deck.
08. Strickler races this...
08. Strickler races this car in races at many different tracks and under many different sanctions, so it races both with and without a spoiler. But if you regularly race without a spoiler, extend the sail panel all the way to the rear of the car if the rules will let you. But if you always run a rear spoiler, shortening the sail panel at the rear will help more air get to the spoiler so it can generate more downforce. Since Strickler races both, he went with the long sail panel.
09. The rules will often...
09. The rules will often allow a maximum hood height that’s higher than the minimum deck height. By taking advantage of this difference, you can create a lip between the hood and the deck like you see here. This ridge creates an aerodynamic dam that catches the high pressure air created by the spoiler and holds it against the deck.
10. Most Dirt Modified rule...
10. Most Dirt Modified rule books don’t allow a dropped deck so we got this shot of a Dirt Late Model. A dropped deck like you see here creates angles to help produce more downforce at the rear of the car, and the downward angled sheetmetal from the sides also helps keep funneled toward the spoiler instead of falling off the sides of the deck.
11. The lack of fenders creates...
11. The lack of fenders creates a small nose, so most Modified racers struggle to create adequate front downforce. One way to increase the efficiency of the front of the car when it comes to down force is to build a chin spoiler that seals against the track to keep as much air as possible from getting underneath the car. And remember, downforce on the straights isn’t where you need it. Make sure the front is sealed to the track when the car is at attitude through the turns.
12. Any air that does get...
12. Any air that does get underneath the car needs to be evacuated out as efficiently as possible. Besides leaving the rear of the car open, you can also open up the left-rear wheel opening as much as possible or raising the lower edge of the left-side rear quarter-panel. On the opposite side of the car, keep the wheel opening on the right rear as tight to the tire as possible to keep the air out.
13. Now that many Dirt Modified...
13. Now that many Dirt Modified classes allow a plastic MD3 aero nose, fabricated noses are often now allowed to have metal fins like you see here. The right side fin helps create side loading, so make sure you have the side of the nose cover as much area as possible and seal off the front suspension as closely as you can get it. Meanwhile, the fin on the left side helps keep the air on the nose to create front downforce.
14. Aerodynamically, the...
14. Aerodynamically, the firewall can be like trying to push a sheet of plywood down the track. You can help guide at least some of the air away from the firewall by creating an angled lower lip below the hood like you see here.
15. Rules will often allow...
15. Rules will often allow some leeway in terms of how the roof is mounted. If you can, create a bit of a lip on the left side between the roof and the window frame while keeping the right side flush. Think of it like a very small Sprint Car winglet. When the car is sliding at an angle through the turns, air hitting this ridge will create downforce, which is nicely centered on the chassis.