Variable Intake System
The flap valves can be set to one of two positions, to produce short or long intake tracts in the intake manifold. Long intake tracts are produced with the flap valves closed. Short intake tracts are produced with the flap valves open. The flap valves are closed at engine speeds up to 4700 rev/min and open at engine speeds of 4700 rev/min and above, with a hysteresis of 50 rev/min.
The tuning valve receives a power feed from the EMS relay in the engine junction box (EJB), and is connected to ground through the engine control module (ECM). To close the flap valves, the engine control module (ECM) connects the tuning valve to ground. The energized tuning valve blanks off the atmospheric vent and opens the vacuum line between the cover plate and the pneumatic actuators. The depression in the intake manifold is sensed at the pneumatic actuators, which turn the drive shafts and move the flap valves to the closed position.
To open the flap valves, the engine control module (ECM) disconnects the ground connection and the tuning valve is de-energized closed. Atmospheric pressure is sensed at the pneumatic actuators through the vent cap on the intake manifold tuning valve and the flap valves move to the open position.
Flap Valves Closed
Flap Valves Open
