Variable Induction System: Description and Operation

Fig. 75 Power Valve Operation:

PURPOSE
The power valve system is used to provide a variable length of intake run.

Power Valve:

LOCATION
Integrated with the intake collector.

CIRCUIT OPERATION
When the engine is running at a low to medium rpm with a heavy load, the ECU energizes the power valve solenoid. The solenoid allows manifold vacuum to act upon the power valve diaphragm, closing the power valve. This increases the length of the intake runner which results in higher engine torque. A surge tank and one-way valve is provided to store vacuum so that the valve will remain closed during low manifold vacuum conditions. When a longer intake run is not needed the power valve is left open to allow a shorter air intake path. This results in improved engine performance in the higher rpm range.

Fig. 145 Vacuum Solenoid:

POWER VALVE CONTROL SOLENOID
The ECU supplies the ground circuit to the solenoid. When the solenoid is energized a plunger is pulled, redirecting vacuum from the source and vent port to the source and valve port allowing vacuum to be applied to the power valve diaphragm.