Be sure to maintain the correct trailing arm angle so that the rear steer from body roll doesn't negatively affect the car. We would move the front end of the arm the same amount as we move the rear in this process.
Data acquisition not only...
Data acquisition not only tells us exactly how our drivers use the throttle, but also how the traction control devices are working. In this example, we see a graph from a Dirt Late Model car at a test at Eldora. The driver is Kevin Weaver and we can see that as the throttle is applied (purple line), the pullbar (red line) begins to extend. Kevin initially applies about 30 percent throttle and then gradually increases throttle all of the way down the straightaway to 100 percent near the end. The engine rpms (black line) never run up, meaning that the rear tires never break loose. The pullbar has controlled the engine torque and the driver has used proper throttle control. This was a very fast lap.
It's not widely known, but some top dirt racers have in the past adjusted their car's engines to produce less horsepower when slick track conditions would not allow great amounts of torque and horsepower to be put to full use. Using smaller carburetors, adding restrictor plates, unhooking the secondary butterflies, or using electronic traction control that changes the timing or breaks down the ignition on one or more cylinders are all ways that teams have of reducing engine output. We've seen teams change to a smaller engine when they knew they were going to a traditionally dry slick track. Again, anything we can do to help the rear tires maintain grip at all times will give us a better chance to apply the power available to accelerate the car.
The Educated Foot
When all available and useable methods of promoting traction control have been applied, the car may still be difficult to apply power to without losing rear traction. In that case, it comes down to drivers using their skills to help prevent loss of rear traction coming off the corners.
Many top drivers have perfected the art of throttle control to help maintain traction. This means that if the driver knows he/she can't apply full throttle without the rear tires spinning, then they will work to apply just enough power to accelerate without breaking the tires loose. This method applies to both dirt and asphalt racing and is much harder to master than most might think. Truth be known, many of our most successful drivers overcame less than perfect setups using this technique.
There's a story told that the late and great Dale Earnhardt was at a test at the Richmond racetrack years ago along with many other teams, one in particular that was having unknown problems and going slow. The struggling team's owner knew Dale and asked him if he would take the car out and see if he could determine what might be the problem. The car had a data recording device installed and one of the functions that the system showed was throttle travel.
Some rear suspension systems...
Some rear suspension systems are designed so that any lateral movement of the rearend causes considerable rear steer. If you need to tighten the car, you can cause lateral movement of the rearend during body squat and roll by reversing the angle of the Panhard bar. This means that the right side, for a right-chassis-mounted Panhard bar, would be mounted lower than the left side. This moves the rearend to the right in the corners and off the corners when the right side of the car moves lower.
Dale promptly went out and ran a full second quicker than the usual driver. Later on, a close review of the throttle graph showed that Dale was rolling on and off the throttle and the graph looked much like a roller coaster. The other driver's throttle graph looked like the New York skyline, straight up and down, or quickly on and off the throttle. He was off the throttle much too quickly going into the corner and had to wait too long to get back into the throttle off the corners until the car was more straight to keep from spinning the tires as he mashed the gas. This example best defines driver induced Traction Control.
Improving traction off the corners is mostly about three things:
Balancing the setup and geometry so that the rear tires are always griping the racetrack so the car is not tight leading to the "tight/loose" syndrome.
Applying one or more traction methods to enhance weight distribution and overall mechanical grip off the corners as needed. This includes reducing the shock to the tires when applying the throttle.
Learn to recognize the amount of traction that is available and help the driver to know when you have done all that is mechanically possible to enhance forward bite. At that point, it's up to the driver to operate the throttle correctly to help further maintain grip between the tires and the track surface.
Your driver may never be able to mash the gas and go, but as Scott Bloomquist once said, "My goal is to go wide-open all of the way around the racetrack. I know that's not possible, but the closer I can get to doing that, the better I like it." Like Scott, learn to develop a legal traction control package that will maximize performance through enhanced traction off the corners. Not only will your lap times get better, the car will be more competitive when trying to get by lapped traffic or when passing for position.