PREVOST X3-45 COMMUTER User Manual

SECTION 12: BRAKE AND AIR SYSTEM
DOB 1300-1556 | X3-45 Commuter PA-1648 Maintenance Manual First release Oct 2020
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21.1 COMPONENTS
The EC-80 controller’s ABS function utilizes the
following components:
• Six (6) Bendix
® WS-24
TM
wheel speed
sensors. Each sensor is installed with a
Bendix Sensor Clamping Sleeve;
• Five (5) Bendix
® Pressure Modulator
Valves (M-40QR);
• Dash-mounted vehicle ABS Indicator
Lamp;
• Service brake relay valve;
• Dash-mounted trailer ABS Indicator
Lamp.
The EC-80 controller’s ATC function utilizes the
following components:
• Drive axle traction control valve;
• TCS status/indicator icon in the DID;
• Dash-mounted TCS Mud/Snow switch;
• J1939 serial communication to engine
control module.
The EC-80 controller’s ESC/RSP function
utilizes the following components:
• Front Axle Traction Control Valve integral
to the service brake relay valve;
• Dash-mounted ESC status/indicator lamp;
• Bendix SAS-70 Steering Angle Sensor
(mounted to the steering column);
• Bendix YAS-70 Yaw Rate/Lateral
Acceleration Sensor (mounted to a cross
member forward of the drive axle);
• Brake Demand Sensors (installed in the
primary and secondary delivery circuits);
• An additional Modulator Valve (Bendix
® M-
40QR
TM
Pressure Modulator Valve) that
controls pressure applied to the trailer
brakes during system intervention.
21.2 BENDIX M-40QR PRESSURE
MODULATOR VALVE
This Bendix
M-40QR (quick release) Pressure
Modulator Valve (PMV) is operated by the EC-
80 controller to modify driver applied air
pressure to the service brakes during ABS,
ATC, RSP or YC activation. The PMV is an
electro pneumatic control valve and is the last
valve that air passes through on its way to the
brake chamber. The modulator hold and release
solenoids are activated to “modulate” or “control”
the brake pressure during an antilock braking
event. The hold solenoid is normally open and
the release solenoid is normally closed, such
that the PMV nominally allows air to flow
through. This design allows for air delivery to
brake chambers in the event of electrical trouble.
This is an "On/Off" type valve, i.e., during an
antilock activity, the valve exhausts air from the
brake chamber when in a ABS event, the
electronic unit senses that the corresponding
wheel speed is decreasing in relation to the
other wheels.
The EC-80 controller also utilizes an additional
PMV for control of the trailer service brakes
during stability interventions.
6s/5m Configuration
Prevost vehicles utilize a 6 sensors/5 pressure
modulator valves configuration, with the tag axle
having two sensors, but only one Pressure
Modulator Valve. In this case, the PMV controls
both wheels on the tag axle. The tag axle wheels
would receive equal brake pressure, based on
the wheel that is currently experiencing the most
wheel slip.
FIGURE 60: M-40QR PRESSURE MODULATOR VALVE

PREVOST X3-45 COMMUTER Specifications

General

Engine	Volvo D13
Transmission	Allison B500
Fuel Type	Diesel
Length	45 ft (13.7 m)
Width	102 in (2.6 m)
Horsepower	500 hp
GVWR	54, 000 lbs
Height	141 in