Brakes - Description
ANTILOCK BRAKE SYSTEM WITH ELECTRONIC STABILITY PROGRAM
This vehicle uses an electronic brake control system designated MK25e. This system includes ABS (Antilock Brake System), TCS (Traction Control System), BAS (Brake Assist System), EVBP (Electronic Variable Brake Proportioning) and ESP(R) (Electronic Stability Program). All of these systems work together to enhance vehicle stability and control in various driving conditions and are commonly referred to as ESP.
This system uses components of the base brake system, but also features the following components:
- Integrated Control Unit (ICU) - Includes Hydraulic Control Unit (HCU) (2) and Antilock Brake Module (ABM) (1)
- Wheel Speed Sensors (WSS) - Four sensors (one at each wheel)
- Dynamics Sensor - Includes a yaw rate sensor and a lateral accelerometer.
- Steering Angle Sensor (SA) - The SAS is part of the Steering Column Control Module (SCCM).
- Brake Pressure Sensor - The brake pressure sensor is located in the HCU and is not serviceable separate from the HCU.
ABS
The purpose of the Antilock Brake System (ABS) is to prevent wheel lockup under braking conditions on virtually any type of road surface. Antilock braking is desirable because a vehicle that is stopped without locking the wheels retains directional stability and some steering capability. This allows the driver to retain greater control of the vehicle during braking.
ALL-SPEED TRACTION CONTROL
The traction control system (TCS) is an all-speed traction control. All-Speed Traction Control enhances mobility and prevents wheel slip when accelerating on slippery surfaces. It also provides a measure of directional stability control. Using the wheel-speed sensors, it can detect excessive yaw and help keep the car on the intended course, as for instance, when accelerating around a curve.
With rear-wheel drive, All-Speed Traction Control is effective up to 85 mph (137 km/h); with AWD, All-Speed Traction Control is effective up to 45 mph (72 km/h), which is common among competitive AWD vehicles with traction control.
ELECTRONIC STABILITY PROGRAM
The Electronic Stability Program (ESP) enhances control and stability of the vehicle under various driving conditions. ESP corrects for over/under steering of the vehicle by applying the brake of the appropriate wheel to assist in counteracting the over/under steer condition. Engine power may also be reduced to help the vehicle maintain the desired path. ESP uses sensors in the vehicle to determine the vehicle path intended by the driver and compares it to the actual path of the vehicle. When the actual path does not match the intended path, ESP applies the brake of the appropriate wheel to assist in counteracting the oversteer or understeer condition.
- Oversteer - When the vehicle is turning more that appropriate for the steering wheel position.
- Understeer - When the vehicle is turning less than appropriate for the steering wheel position.
The "ESP/TCS" indicator light located in the instrument cluster starts to flash as soon as the tires lose traction and the ESP system becomes active. The "ESP/TCS" indicator light also flashes when TCS is active.
The ESP can be turned off by using the ESP Off switch. When the ESP Off switch is depressed, it does not completely turn the system off. The ESP system shuts off engine management but retains brake activations for yaw control.
The SRT8 equipped vehicles have three-mode ESP functionality. When the ESP Off switch is depressed and quickly released, the system enters "partial" mode which has no engine management but retains brake activations for yaw control. If the switch is held down for a period of five seconds or longer before releasing, a chime will sound and the ESP system enters "full-off" mode which disables engine management as well as brake activations. The system can be returned to "normal" by briefly pressing and releasing the ESP Off switch. The system will default to full-on mode at the beginning of each ignition cycle.
BRAKE ASSIST SYSTEM
The Brake Assist System (BAS) is designed to optimize the vehicle's braking capability during emergency braking maneuvers. The system detects an emergency braking situation by sensing the rate and amount of brake application and then applies optimum pressure to the brakes. This can help reduce braking distances. The BAS complements the antilock brake system (ABS). Applying the brakes very quickly results in the best BAS assistance.
ELECTRONIC VARIABLE BRAKE PROPORTIONING
Electronic Variable Brake Proportioning (EVBP) is used to balance front-to-rear braking in place of a traditional rear proportioning valve. The EVBP system uses the ABS system to control the slip of the rear wheels in partial braking range. The braking force of the rear wheels is controlled electronically by using the inlet and outlet valves located in the integrated control unit (ICU).
EVBP activation is invisible to the customer since there is no pump motor noise or brake pedal feedback.