Bendix Commercial Vehicle Systems EC-60 ATC STD/PREM CONTROLLERS - Manual (Page 7)

7
Normal Braking
During normal braking, brake pressure is delivered through
the ABS PMV and into the brake chamber. If the ECU
does not detect excessive wheel slip, it will not activate
ABS control, and the vehicle stops with normal braking.
Retarder Brake System Control
On surfaces with low traction, application of the retarder can
lead to high levels of wheel slip at the drive axle wheels,
which can adversely affect vehicle stability.
To avoid this, the EC-60
™ controller switches off the retarder
as soon as a lock-up is detected at one (or more) of the
drive axle wheels.
When the ECU is placed in the ABS off-road mode, it will
switch off the retarder only when ABS is active on a steer
axle wheel and a drive axle wheel.
Optional ABS Off-Road Mode
On some road conditions, particularly when the driving
surface is soft, the stopping distance with ABS may be
longer than without ABS. This can occur when a locked
wheel on soft ground plows up the road surface in front of
the tire, changing the rolling friction value. Although vehicle
stopping distance with a locked wheel may be shorter than
corresponding stopping distance with ABS control, vehicle
steerability and stability is reduced.
Premium EC-60
™ controllers have an optional control
mode that more effectively accommodates these soft road
conditions to shorten stopping distance while maintaining
optimal vehicle steerability and stability.
WARNING: The ABS off-road mode should not be
used on normal, paved road surfaces because vehicle
stability and steerability may be reduced. The flashing
ABS Indicator Lamp communicates the status of this mode
to the driver.
The vehicle manufacturer should provide the optional ABS
off-road function only for vehicles that operate on unpaved
surfaces or that are used in off-road applications, and is
responsible for ensuring that vehicles equipped with the
ABS off-road function meet all FMVSS-121 requirements
and have adequate operator indicators and instructions.
The vehicle operator activates the off-road function with a
switch on the dash panel. A flashing ABS Indicator Lamp
indicates to the driver that the ABS off-road function is
engaged. To exit the ABS off-road mode, depress and
release the switch.
All-Wheel Drive (AWD) Vehicles
AWD vehicles with an engaged interaxle differential (steer
axle to rear axle)/AWD transfer case may have negative
effects on ABS performance. Optimum ABS performance
is achieved when the lockable differentials are disengaged,
allowing individual wheel control.
Premium EC-60
™ controllers can be programmed specifically
for this configuration to control the differential lock/unlock
solenoid in the AWD transfer case. When programmed to
do so, the ECU will disengage the locked interaxle/AWD
transfer case during an ABS event and reengage it once
the ABS event has ended.
ATC OPERATION
ATC Functional Overview
Just as ABS improves vehicle stability during braking,
ATC improves vehicle stability and traction during vehicle
acceleration. The EC-60 ™ controller ATC function uses the
same wheel speed information and modulator control as
the ABS function. The EC-60 ™ controller detects excessive
drive wheel speed, compares the speed of the front, non-
driven wheels, and reacts to help bring the wheel spin under
control. The EC-60 ™ controller can be configured to use
engine torque limiting and/or differential braking to control
wheel spin. For optimal ATC performance, both methods
are recommended.
ATC Lamp Operation
The ATC Lamp Illuminates:
1. During power up (e.g. when the vehicle is started) and
turns off after the self test is completed, providing no
diagnostic trouble codes are present.
2. When ATC is disabled for any reason.
3. During an ATC event (the lamp will flash rapidly). When
ATC is no longer active, the ATC active/indicator lamp
turns off.
4. When the ECU is placed in the ATC off-road mode (the
lamp will flash at a rate of 1.0 seconds on, 1.5 seconds
off). This notifies the vehicle operator that the off-road
mode is active.
Differential Braking
Differential braking is automatically activated when drive
wheel(s) on one side of the vehicle are spinning, which
typically occur on asphalt road surfaces with patches of ice.
The traction system will then lightly apply the brake to the
drive wheel(s) that are spinning. The vehicle differential
will then drive the wheels on the other side of the vehicle.
Differential braking is available at vehicle speeds up to
25 MPH.