Density controller system
 engine idle, oil pressure forces the exhaust
bypass valve butterfly closed.
engine
operating at higher speed, the turbocharger supplies compressed air to
the intake manifold until the proper absolute pressure is reached. At this
point, the pressure on the bellows begins to open the metering valve. This
reduces the pressure on the piston in the actuator and the spring force
causes the butterfly valve to move toward open.
engine
operation. The density controller has temperature sensitivity as well as
pressure sensitivity. As compressor temperature decreases, the
controller boot bellows senses the lower temperature and causes the metering
valve to move off its seat. This causes the engine cruising at altitude.
When cruising at altitude the turbocharger supplies compressed air to the
intake manifold as required by the altitude and temperature of the air.
The amount of turbocharger output is determined by the position of the
butterfly of the exhaust bypass valve. The proper absolute pressure will
cause a certain amount of pressure on the controller bellows. This pressure
tends to lift the metering valve off its seat to prevent the compressor
pressure from getting too high. It also lifts when the compressor
temperature is too low. As the valve moves off its seat, it reduces
the engine oil pressure and the butterfly valve opens somewhat. Thus, the
turbocharger is maintained at predetermined levels.
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