Recently I have been having some discussions with others about driver aids – specifically traction control and anti-lock brakes (ABS). The consensus seems to be that driver aids take away from the driver’s raw interaction with the car, and they make the car softer and simpler car to drive. I thought it would be an interesting topic to discuss.
First up is traction control. With traction control, you use the engine control unit (ECU) to selectively cut ignition to cylinders, to reduce the power output of the engine when a certain level of wheel spin is detected. Traction control in a proper racecar is nothing like a street car, the latter of which tries to shut down the entire car upon detection of slip. No matter how skilled or talented the driver, there is no physically possible way that a driver can modulate the throttle to anticipate the traction the car has or will have in the next hundredths of a second. Bumps in the road, surface changes, tire condition and, of course, driver inputs all affect the amount of tractive force the tires can put down. And the tractive force applied changes both with gear and RPM, even at wide open throttle.
As a result, even the best drivers have to compensate in order to not exceed the traction limit under acceleration. Some amount of tire slip is acceptable and common, but allow too much and you overheat the tires and get the car into a slide – which costs far more time than running with a little bit of a buffer.
Traction control, on the other hand, requires much the same driving technique, but it allows the driver to be ever so slightly more aggressive. Any bumps in the road that would normally result in the start of heavy wheel spin are controlled by the ECU at a rate so fast the human brain can hardly process each control event. The driver (if he has confidence in the system) can keep his foot in it and not worry about overheating tires or getting into a big slide. I have to tell you, a properly tuned traction control system is incredibly fun to drive. It also makes for a more consistent car.
ABS produces a similar, but more substantially more significant effect. While traction control really only comes into play in slower corners when the car has a lot of torque to spin the tires, ABS comes into play in all braking zones. And, unlike traction control, ABS allows the car to do something the driver cannot physically replicate – it can reduce braking force on the inside wheels.
Aside from keeping the car from locking up in a straight line and flat spotting the tires, ABS also allows the car to trail brake into the corner deeper than a car without it. With a traditional system, as the driver trails in (braking and cornering at the same time) and unloads the inside tires, the braking capability of the two sides of the car are no longer equal. The outside tires are capable of applying more brake, but applying additional brake force will lock either the inside front or inside rear tire (typically the inside front of a RWD car, and the inside rear on a FWD car). With traditional systems, the driver has to give up some brake force while cornering to keep from flat spotting the inside tires. An ABS system can reduce the braking force on those inside wheels, allowing the driver to carry more speed into the apex.
No matter how talented the driver is he or she cannot overcome this reality, and as a result, an ABS system will always be faster. Additionally, an ABS system (similar to traction control) can control wheel lockups from bumps and surface changes instantaneously, whereas a human driver must compensate before the limit in order to avoid wheel lock-up.
So in the case of absolute speed, racecars with traction control and ABS should always be faster, even with the best driver on the planet. They are not necessarily “aids” as much as electronic systems that optimize the performance of the car.
But if we want to talk about driver aids in racing, for excitement of the sport, we can all agree that watching drivers dance around the limit of traction while also battling inches away from each other and managing tire wear is far more exciting than watching cars that are so consistent that passing becomes almost impossible. After all, locking wheels and sliding cars is one of the most awesome things about racing!