There are many different systems within cars that help to make them safer to drive, and two of the most common are both concerned with the way the car handles when pushed close to the limits of traction. But what are the differences between Electronic Stability Control (ESC) and Traction Control?
The 3 main differences between Electronic Stability Control and Traction Control are:
- Traction control is used to limit wheelspin
- ESC is used to help guide the car in the right direction
- Traction control may use other components while ESC usually only uses the brakes
This is a simple way of saying what each of these systems do, but more differences arise when you consider how they work and their applications. So, let’s look into each in more detail, and find out where each one comes into play when driving.
What Is Electronic Stability Control?
Electronic Stability Control, or ESC, is also sometimes called Electronic Stability Program (ESP) or Dynamic Stability Control (DSC). This system detects and reduces loss of traction. It does this via a complex system of sensors, that monitor the amount of grip experienced by each wheel.
It then uses automatic application of the brakes at individual wheels to guide the car in the right direction, which we will discuss in more detail below. It may also reduce the power of the engine in some cars, but it usually only uses the brakes. ESC does not improve cornering, and instead only minimizes the loss of control that the car experiences.
What Is Traction Control?
Traction control is designed to specifically prevent the loss of traction when the car is accelerating. Wheels can lose grip for a variety of different reasons, and intense acceleration can be one of them. Traction control applies the brakes to the wheels that have lost traction in order to regain it and allow the car to accelerate effectively.
Traction control systems are often more complex than a simple application of the brakes however, and they often involve power reduction within the engine itself. This can itself involve a reduction of the spark sequence inside the individual cylinders of the engine, or it can be used to reduce the fuel supply, which would also limit the power delivered to the wheels.
When Is ESC Used?
Minimizing The Loss Of Control
As we have discussed already, electronic stability control systems are used to minimize the loss of control experienced by the driver, and they do this by intervening with the amount of power experienced by the wheels. The brakes are applied to the individual wheels in the way that the ESC system ‘thinks’ will help to allow the car to go in the right direction.
This is the main idea behind the electronic stability control system, as it is used in situations when the car is not travelling in the direction that the driver intends. It does this by measuring the angle that the steering wheel should be making the car turn and compares it to the amount that the front wheels are turning and by measuring the amount of traction at each wheel.
The wheels that the ESC applies the brakes to will depend on the way that the car is losing control. If the car is going into an oversteer situation for example, the brakes will be applied to the outer front wheel. This is because, as the rear wheels lose traction, the front wheels have more grip, and which one of these have more grip can affect the direction the car travels.
As the back end slides out, towards the left-hand side, the ESC system will apply the brakes to the front left wheel. This will cause this wheel to experience more grip and hold the front left-hand side of the car to the ground. This will create torque about the vehicle’s vertical axis, which can be thought of as a line straight down the middle of the car from the front to the back.
This grip at the front left tire will act to pull on the opposite tire – the back-right tire – which pulls the rear-right corner of the car towards the front left. As the car begins to straighten up, the ESC performs this application and release of the brakes several times per second, and the fine tuning of the system means that the back end should straighten up without sliding the other way.
If the car goes into an understeer situation, and for example the driver is trying to turn left but the car continues to travel straighter, then the ESC will work in the opposite way. In this case, the driver wants to snap the front of the car back in the direction he wishes to travel, and this can be active by the ESC providing more grip, through braking, to the left rear wheel.
By applying the brakes to the left rear wheel, it will experience more grip, and the opposite tire, in this case the front right tire, will be pulled towards the left-hand side, aiding in the car’s turn. It is this generation of torque across the middle axis of the car that forces the car in the intended direction. Although not always perfect, this can help the driver to regain control.
When Is Traction Control Used?
Loss Of Traction
Traction control is activated when the car detects a loss of traction, rather than a loss of control. Although this can often be indistinguishable from a loss of control, and both ESC and traction control can indeed turn on in the same circumstances, traction control is most often applied when the car loses traction due to intense acceleration.
The car can lose grip due to a number of reasons, such as an uneven road surface or if it is wet. However, when the car is accelerating, such as during a race when the driver may put his foot to the floor when exiting a corner, a slight loss of traction may cause the wheels to spin. This means that not all of the power is being transferred to the tires onto the road.
Limit The Power
To combat this, traction control turns on to limit the power being supplied to the turning wheels. As we have already mentioned, it can do this by applying the brakes or by temporarily reducing the power of the engine. It is also used most often during a corner and particularly upon the exit, when the driver goes from a relatively slow speed to much faster in a short space of time.
If you are driving a front wheel drive car, and corner quite aggressively, you will be at risk of going into an understeer situation. this is because as you accelerate, the weight of the car shifts towards the rear, and the front tires are prone to losing traction. This reduces their ability to turn effectively, and so the car continues in a straight line as you turn the wheel.
Rear Wheel Drive
Rear-wheel-drive cars are more susceptible to oversteer. This is because, although the weight is transferred to the back of the car under acceleration, the rear tires may break this increased traction through rapid acceleration, causing wheelspin. Traction control works to reduce the power at the rear in this case, allowing the spinning wheels to regain traction and break out of the oversteer.
Front Wheel Drive
In the case of the front-wheel-drive car experiencing understeer, the traction control limits power to the front wheels, causing them to grip the road and regain the traction that they need in order to turn the car. Although both types of car can experience both over and understeer, they are more likely to experience one or the other under extreme acceleration.
Traction control thus has its use in a race car as it allows for more grip at the exit of a corner when the driver presses the accelerator hard. For this reason, some motorsports limit the use of traction control, such as Formula 1 which banned it completely in 2008.
Disadvantages Of ESC
ESC does have the issue that it can make drivers complacent, as they may feel like they can push their car further than its limits. The problem is that ESC does not always save the car from losing control, and with extreme speeds and sharp turning the car will still inevitably lose control. Thus, ESC cannot be treated as a complete fail safe, and there is no substitute for safe driving.
In race cars, ESC is not always useful, as a lot of drivers may prefer to use understeer and oversteer within their driving style. ESC will limit their ability to use either one, or if it comes on at high speeds the car could snap back into a straight line unexpectedly. This could prove dangerous at high speeds with other cars around you.
Disadvantages Of Traction Control
Traction control also presents the possibility of driver complacency, as they may feel like they can push their car past its traction limits when accelerating. Also, in off-road situations, you may actually want the wheels to spin in order to get you out of some situations, such as when the car is stuck in mud.
If used on the track, it may limit the car’s power at the wrong time, similar to the way that the ESC system may cause the car to straighten up at an undesirable time. This could cause the driver to lose vital milliseconds, which add up over the course of a race. Not only that, but the system can be expensive to repair if anything goes wrong.
Electronic stability control and traction control are two systems used within cars to give the driver more control in certain situations. ESC is used to prevent or reduce the loss of control through oversteer and understeer, while traction control is used to give the tires more grip under intense acceleration. Although they work in similar ways, they have very different applications.