A traction control system (TCS), on current production vehicles, is typically electro-hydraulic systems designed to prevent loss of traction and therefore the control of the vehicle when the driver applies excessive throttle or steering. Although similar to electronic stability control systems, traction control systems do not have the same goal.
The intervention can consist of any, or all, of the following:
- Retard or suppress the spark to one or more cylinders
- Reduce fuel supply to one or more cylinders
- Brake one or more wheels
- Close the throttle, if the vehicle is fitted with drive by wire throttle.
- In turbo-charged vehicles, the boost control solenoid can be actuated to reduce boost and therefore engine power.
Typically, the traction control system shares the brake actuator and the wheel speed sensors with the anti-lock braking system.
Use of traction control
In road cars:
Traction control has traditionally been a safety feature in high-performance cars, which would otherwise need very sensitive throttle input to keep them from spinning when accelerating, especially in wet or snowy conditions. In recent years, traction control systems have become widely available in non-performance cars, minivans, and light trucks.
In race cars:
Traction control is used as a performance enhancement, allowing maximum traction under acceleration without wheel spin. When accelerating out of turn, it keeps the tires at the optimum slip ratio.
In off road vehicles:
Traction control is used instead or in addition to the mechanical limited slip or locking differential. It is often implemented with electronic limited slip differential, as well as other computerized controls of the engine and transmission. The spinning wheel is slowed down with short applications of brakes, diverting more torque to the non-spinning wheel. This form of traction control has an advantage over a locking differential as steering and control of a vehicle is easier, so the system can be continuously enabled. It also creates less stress on the drive train, which is particularly important to the vehicles with an independent suspension that is generally weaker compared to solid axles. On the other hand, only half of the available torque will be applied to a wheel with traction, compared to a locked differential, and handling is less predictable.
It is widely thought that TC removes some skill and control from the driver. As such it is unpopular with many motorsports fans. Some motorsports series have given up trying to outlaw TC. With current state of technology, it is possible to implement TC as a part of software in ECU, and as such it is very hard to detect by scrutineers. Very effective yet small units are also available through a company in the US, Davis Technologies that allow the driver to remove the traction control system after an event if desired. In Formula One, an effort to ban TC has led to the change of rules for 2008: every car must have a standard ECU, issued by FIA, which is relatively basic and does not have TC capabilities.