Teledyne TSIO-360-RB, Maintenance Manual

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11-6
11-4 VARIABLE ABSOLUTE PRESSURE CONTROLLER (VAPC) DETAILED DESCRIPTION.
The variable absolute pressure controller is designed to maintain deck pressures to provide
sea level horsepower at varying altitudes. By means of a sensing port in the pneumatic
section of the controller, the outside of the aneroid bellows is subjected to deck pressure.
The aneroid bellows is linked to a poppet valve, spring loaded normally closed. As pressure
differences occur, the poppet valve readjusts, changing the amount of restriction to oil flow
from the wastegate. As the restriction of oil flow occurs, pressure in the hydraulic portion of
the wastegate increases, causing the wastegate butterfly valve to close, increasing exhaust
gas flow to the turbocharger turbine.
The Variable Absolute Pressure Controller consists of a poppet valve (controlling oil flow),
referenced to a pressure sensitive bellows on one side and a mechanically actuated, spring
loaded plunger on the other. The mechanical actuated plunger is connected through a
series of cams, levers and link rods to the throttle plate.
The VAPC is installed on the engine intake manifold, prior to the throttle plate, and in such a
way that the pressure sensitive bellows is in the intake manifold and senses turbocharger
compressor discharge pressure (deck pressure).
During engine operation compressor discharge pressure is referenced by the VAPC’s
bellows while the mechanically linked plunger is positioned according to throttle plate
position. When ever the compressor discharger pressure sensed by the bellows is less
than the mechanical and spring pressure acting on the plunger the poppet valve is
positioned to restrict oil flow from the wastegate actuator to the engine and the wastegate
butterfly valve goes closed. If the compressor discharge pressure sensed by the bellows is
greater than the mechanical and spring pressure acting on the plunger the poppet valve
moves to a position that increase oil flow from the wastegate actuator to the engine and the
wastegate butterfly valve opens.
During cruise operation, the forces acting on the poppet valve are stabilized. Thus, the oil
flowing from the wastegate actuator through the VAPC is constant and the wastegate
butterfly valve is positioned in a intermediate position maintaining the selected compressor
discharge pressure and manifold pressure.
FIGURE 11-5. VARIABLE ABSOULUTE PRESSURE CONTROLLER