Bendix Commercial Vehicle Systems BA-921 COMPRESSOR_STD/CLOSED ROOM - Manual (Page 6)

6
AIR INDUCTION
Section 1: For Standard Compressors.
GENERAL
The Standard Bendix ® BA-921 ® air compressor can be used
both with air induction systems that are naturally aspirated
(atmospheric air) and pressurized (turbocharged). The
following section covers Caterpillar and Detroit Diesel
engine air induction arrangements. See Figure 5, for
typical fl anges used.
CATERPILLAR
Caterpillar HD ACERT engines (C11, C13, C15 and C18)
and MD ACERT engines (C7 and C9) are typically equipped
with Bendix
® BA-921 ® compressors. These engines
provide pressurized (turbocharged) air to the compressor's
inlet port. Caterpillar recommends the use of an inlet
check valve in the air induction system to prevent the air
from the compressor being forced back into the engine
air induction system when the compressor is operating in
the "unloaded" condition (not building air). Because the
compressor induction system is turbocharged, an additional
air volume is required between the compressor inlet port
and the inlet check valve to prevent excessive air pressure
at the compressor inlet in the unloaded mode. Figures 12
and 13 show examples of the different air induction systems
used by Caterpillar to perform this function.
CATERPILLAR C7/C9 ENGINES
The Bendix ® BA-921 ® compressor in the C7/C9 air induction
system (see Figure 12) receives its air from the engine's
intake manifold (turbocharged). During the pumping
condition (loaded mode), the air fl ows from the engine
intake manifold through the inlet check valve and inlet
line to the compressor inlet port. During the non-pumping
condition (unloaded mode), the compressor cylinder
pushes air back out of the inlet port to the inlet check valve.
The ICV prevents the air from traveling beyond this point.
Because the air is boosted (under pressure), it is important
that the compressor inlet line is of suffi cient length, strength
and volume to minimize the build-up of air pressure in the
inlet system. The air shuttles back and forth between the
compressor cylinder bore and the ICV during this phase
of the compressor operation.
FIGURE 12 - EXAMPLE OF CATERPILLAR (ACERT
ENGINE) C7/C9 COMPRESSOR AIR INDUCTION SYSTEM
(TURBOCHARGED)
Inlet
Port
Inlet Check Valve
Inlet
Line
Air Supply
From Engine
FIGURE 13 - EXAMPLE CATERPILLAR (HD ACERT
ENGINE) C11/C13/C15/C18 COMPRESSOR AIR INDUCTION
SYSTEM (TURBOCHARGED)
Inlet
Port
Expansion Tank
Inlet Check Valve
Air Supply
From Engine
Inlet
Line
FIGURE 14 - EXAMPLE OF DETROIT DIESEL (EGR) S60
COMPRESSOR AIR INDUCTION SYSTEM (NATURALLY
ASPIRATED)
Inlet
Port
Inlet
Check
Valve
A
Fr