Brake Booster; Emergency Brake Assistant (Eba); Components - Ford 2007 WQ Fiesta Repair Manual

206-0713
Power Brake Actuation
206-0713
DESCRIPTION AND OPERATION
Brake Booster
Emergency brake assistant (EBA)
EBA operates purely mechanically, and is
completely integral with the brakeservo.
As ABS braking systems have become widespread,
it has emerged that because of incorrect use of the
Brake servo units with and without EBA are
brakes, many drivers are losing the safety benefit
externally identical. For identification purposes,
which ABS ~rovides.
brake servo units with EBA carry a white sticker
I
showing a large letter " A .
Drivers are applying the brakes too timidly.
Because of this, the Anti-lock Braking System
The tandem master cylinder is the same for
(ABS) does not engage, and the maximum braking
vehicles with or without
effect is not achieved.
The EBA recognises from the driver's manner of
braking that an emergency situation is occurring,
and automatically applies full braking power.
This occurs in a matter of milliseconds, which is
faster than the driver could do it.
Furthermore, it was observed that after the first
heavy application of the brake pedal, the driver
releases the pressure on the pedal too early.
The EBA ensures that the ABS effect still continues
when the pedal pressure would normally lie below
the ABS range of control. The system is available
j
as an option depending on market and vehicle
variant.
Function
In normal braking situations, the brake servo with
EBA operates in the same way as a conventional
brake servo unit. This means that the driver can
always modulate the brakes.
If an activation threshold defined by a characteristic
curve is exceeded during braking, the EBA
operates.
Determination of the activation threshold is based
on the pedal movement parameters, which are a
function of the pressure on the brake pedal and
the speed of movement of the pedal.
Depending on driving manner, EBA results in a
The characteristic curve is separately defined for
reduction in braking distance of 15% for
each vehicle model.
experienced drivers, to over 40% for average
The mechanical EBA uses the fact that in a brake
drivers.
servo unit, the valve piston moves ahead of the
Because EBA decelerates the vehicle up to the
control housing when a braking operation starts.
wheel locking limit, emergency brake assist is only
Because of this, there is a relative travel distance
used in vehicles with ABS.
between the control housing and the valve piston
which can vary depending on the force applied to
Components
the brake pedal and the pedal speed.
The relative travel distance is small when the pedal
moves slowly with low force applied to it. The
relative travel distance is larger when the pedal
moves faster with higher force applied to it.
Item Description
-
2006.0 Fiesta
1212006 GI 63289en