VMAC - Vehicle Mounted Air Compressors
VMAC Technical Support: 888-241-2289
VMAC Knowledge Base: www.kb.vmacair.com
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Performance Testing and System
Adjustments
Performance Testing and System Adjustment
System operation can be tested using the tools that will be operated by the system
or by using the VMAC Test Tool (A700052) with the 70 cfm (0.190 in) orifice in the
outlet to simulate tool use (Figure 58).
Disconnect all downstream equipment (hose reels, etc.) and connect
the test tool directly to the discharge fitting on the AOST.
Ensure there are no leaks in the test tool. The system may not idle
down if there are leaks in the lines or fittings.
Figure 58 — A700052 VMAC Air Test Tool
Install orifice here
Orifice
Ball valve
JIC Adapters
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Install the VMAC test tool at the AOST outlet with the 70 cfm (0.190) orifice.
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Ensure that the ball valve is closed.
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Place the transmission in “PARK” and fully apply the park brake.
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Allow the engine to run until it is at operating temperature.
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Turn on the air compressor system and allow it to operate until the oil is warm.
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Observe the pressure gauge. Pressure should be approximately 150 psi.
Open the ball valve on the test tool and observe the engine tachometer:
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Analog throttle control
: Engine speed should increase to approximately
1,800 rpm – 2,200 rpm.
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Digital throttle control:
Engine speed should increase to approximately
2,400 rpm.
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Close the air valve slowly to allow the system pressure to rise. When the
pressure reaches 150 psi (factory setting), the system will close the inlet valve
poppet and reduce the engine speed to VMAC base idle (approximately
1,000 rpm).
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Once the system pressure is at maximum, slowly open the ball valve on the
test tool until the pressure on the gauge begins to drop. Engine speed should
ramp up when the pressure drops to approximately 140 psi. This value can
be adjusted via the “IDLE DOWN PRESSURE” (analog throttle) / “RAMP UP
PRESSURE” (digital throttle) adjustment.
