Volkswagen Magazine

All Systems Go!

Volkswagen embraces the road, in all its many conditions—winter driving included. In fact, VW has created a suite of safety systems that ensure your drive is as safe as it can be.
Have you ever wondered what they all mean? Here’s an explanation.

ELECTRONIC STABILITY CONTROL (ESC)

Electronic Stability Control puts safety first in all critical situations by automatically applying the brakes on individual wheels to keep the vehicle heading in the right direction. (In fact, ESC is a function of the ABS control unit—more on that below.) Whether it's an elk in the middle of the road or some other unforeseen event, ESC helps you to maintain better control and stay on track when you are forced to make an evasive manoeuvre.

ESC builds on other electronic systems, such as the anti-lock braking system (ABS) and ASR traction control system. It takes driving safety a step further—controlling lateral dynamics and helping to prevent oversteering or understeering by applying corrective forces to each of the wheels.

These braking interventions are performed almost instantly and last only a fraction of a second. The brain controlling the interventions is the system computer that receives information from a yaw rate sensor on whether and how the vehicle is rotating about its vertical axis. Other sensors also supply important data to the computer: a steering angle sensor, a lateral acceleration sensor and four wheel sensors. Using the data from these sensors, the system computer detects any differences between target values and actual values, and acts as an electronic guardian angel, initiating the necessary

TRACTION CONTROL (ASR)

For high-torque engines, traction control offers more comfort and safety, particularly when driving on slippery roads or surfaces with differing degrees of grip. The traction control system facilitates smooth starting and acceleration over the entire speed range, without wheelspin or fishtailing.

The traction control system operates in tandem with the electronic accelerator (EGas) and uses the wheel speed sensors of the anti-lock braking system (ABS). If a sudden increase in speed is detected at one of the drive wheels, the traction control intervenes in the engine management system to counter this effect by throttling back engine power.

Traction control assures good traction and directional stability in the acceleration phase across the entire speed range, and thus promotes active safety. In addition, it reduces tire wear. Traction control also incorporates the electronic differential lock (EDL) and makes up part of the electronic stabilization program (ESP).

ANTI-LOCK BRAKING SYSTEM (ABS)

When a driver brakes hard on a slippery road surface, the anti-lock braking system prevents the wheels from locking so that the vehicle can still be steered. When the wheels lock up, they are no longer able to transmit cornering forces, so the driver loses control. To prevent this, the ABS control unit uses wheel speed sensors to monitor the rotational speed of each wheel. If it detects that a wheel is about to lock, a solenoid valve in the anti-lock braking system’s central control reduces the brake pressure applied to the wheel in question, until it starts to rotate freely again. The pressure is then increased to the lock-up threshold once again. The vehicle remains stable and can still be steered. The latest anti-lock braking systems fitted in all Volkswagen models repeat this action several times per second.

Drivers can tell when the anti-lock braking system is working by a slight vibration of the brake pedal. But the vehicle is still fully steerable so the driver can avoid obstacles or collisions with other vehicles.

4MOTION

4MOTION is an all-wheel drive system that improves traction reserves, even in bad weather or on rough roads. It increases ride stability and provides outstanding straight-line running and opti- mum side wind stability. 4MOTION not only offers decisive traction benefits, but also enables higher cornering speeds, thereby enhancing both safety and driving enjoyment—always depending on road conditions, of course.

Depending on the design, the core of an all-wheel drive system is usually a differential between the front and rear axles—the so-called centre differential. It distributes driving forces variably across the front and rear axles. If rotation speeds differ between the two axles (because one of them is slipping on icy or gravelly surfaces, for example), the system distributes torque accordingly, diverting a portion of it to the other axle as required. At the same time, minor differences in rotation speed during cornering or manoeuvring also have to be compensated for to prevent torsional stresses in the drive train.