Anti-lock braking system (ABS), BTCS and EBD

ABS and BTCS improve active driving safety, with BTCS replacing the mechanical rear brake pressure regulator. ABS provides full control under heavy braking, while BTCS improves vehicle stability when accelerating on slippery road surfaces. The next active safety feature in today's compact cars is electronic brake force distribution (EBD). The EBD is activated before the ABS works and stabilizes the car's motion when braking, it electronically precisely regulates the rear wheel spin. Fiesta's anti-lock braking system (Teves MK 20) includes electronic and hydraulic units (EHCU), which are housed in a single aluminum alloy housing. To accurately measure wheel speed, the EHCU uses four sensors, one for each wheel. The same signals are used by the EBD and BTCS systems. The EHCU controls eight solenoid valves, one hydraulic pressure pump driven by a DC motor, and two hydraulic accumulators. The Teves MK 20 system controls all wheels up to a vehicle speed of 120 km/h. On the rear axle, the system functions in parallel, i.e. each time, the wheel that is first prone to blocking is used as the reference. In the presence of malfunctions, the ABS, EBD and BTCS systems are disabled and the brake system works without electronic support, like a conventional brake system. The presence of a malfunction is signaled by the ABS warning lamp: it does not go out after a mandatory self-test. The Fiesta ABS system has a self-diagnostic function, fault codes are stored in memory and, if necessary, are called from it.

Electronic dual circuit pump

The braking force is distributed in the system by an electronic dual-circuit pump. There are two solenoid valves in each of the four separate control channels (inlet and outlet). Normally the intake valves are open and have an adjustable orifice (small orifice for fine adjustment of low fluid flow, large orifice to create minimal hydraulic resistance during normal operation of the brakes).

The EHCU system controls the operation of the ABS

The EHCU system controls the operation of the ABS, calculates the vehicle speed based on the signals received from the wheel speed sensors, manages all electronic components and stores information about malfunctions. With the ignition on, the EHCU performs a self-test before driving. All electronic connections are monitored while driving. In this case, the polarity of the power sources, the presence of a short circuit and breaks in the electrical circuit are checked. The ABS solenoid valves are checked simultaneously and continuously, for which the system sends a test pulse. In the service center, possible faults are read using the FDS 2000.

EBD system limits rear wheel spin

Before the main system is activated, the EBD system regulates the limitation of rear wheel spin. The system compares the slip of the front and rear wheels and doses or distributes the braking force accordingly. Normally the operation of the EBD system is imperceptible, as it works with minimal braking depending on the condition and load of the vehicle. In addition, the EBD system replaces the conventional rear brake pressure regulator.

BTCS is active up to 50 km/h

The BTCS system with two shut-off solenoid valves and two hydraulic inlet valves is integrated into the ABS system. If necessary, this system is activated at vehicle speeds up to 50 km/h. It functions as long as it is necessary to start the car from a standstill and accelerate on slippery road surfaces. The BTCS system creates conditions for maximum torque transfer to the front wheels, which improves the vehicle's handling during smooth acceleration from a standstill, especially when maneuvering. If the BTCS detects a front wheel spin, it will immediately command that wheel to brake.