Intake Air Distribution and Filtering
Intake Air Distribution and Filtering
COMPONENT LOCATION
INTRODUCTION
The intake air distribution and cleaning system comprises:
- Dual air intakes, air cleaners and air ducts.
- An intake manifold.
AIR INTAKES, AIR CLEANERS AND AIR DUCTS
Air is supplied to the air cleaners through the air intakes, air intake hoses and dirty air ducts in the fenders.
The air cleaners are located in the engine compartment, forward of the suspension housings. Two isolators locate each air cleaner on the related front side member. Each air cleaner consists of an air cleaner element installed in a tray and enclosed with a cover secured by six screws. Air inlet and outlet connections are incorporated into the tray and cover respectively. The bottom of the tray incorporates a drain valve to prevent the accumulation of water in the air cleaner. The air outlet connection incorporates a MAFT (mass air flow and temperature) sensor.
Air Cleaner
The clean air convolutes and the clean air duct direct the air from the air cleaners into the electric throttle. Hose clamps connect the clean air convolutes and the clean air duct together, and to the air cleaners and the electric throttle.
The clean air duct also incorporates the following:
- Resonators, to reduce air induction noise.
- A connector stub for the engine full load breather pipe.
INTAKE MANIFOLD
The intake manifold is installed between the cylinder heads and directs air from the electric throttle to the individual cylinders. The inlet port connects to a central chamber in the intake manifold. Eight separate tracts connect the central chamber to the outlet ports. A cover plate seals the rear of the intake manifold.
The intake manifold incorporates:
- A stub pipe for connection of the part load breather.
- A stub pipe for connection of the evaporative emissions system.
- A MAP (manifold absolute pressure) sensor.
- A vacuum connection for the brake booster.
- Threaded inserts to provide attachment points for the electric throttle, fuel crossover tube, engine cover and an engine harness shield.
- Compression limiters in the cylinder head attachment points.
- Seals in the inlet and outlet ports.
- A VIS (variable intake system).
Variable Intake System
The VIS changes the length of the tracts in the intake manifold to improve the air flow to the cylinders, which improves the engine power and torque.
A cassette in the intake manifold contains eight flap valves, each located in an opening part-way along one of the tracts. Two drive shafts connect the flap valves together in two groups of four. Each drive shaft is connected to a pneumatic actuator installed on the cover plate of the intake manifold.
A tuning valve, also installed on the cover plate, controls the application of vacuum pressure to the pneumatic actuators. The tuning valve is a normally-closed solenoid-operated valve installed in the vacuum line between the cover plate and the pneumatic actuators. A vent cap on the tuning valve allows atmospheric pressure into the vacuum line to the pneumatic actuators when the tuning valve is closed.
The ECM (engine control module) controls the operation of the tuning valve.
CONTROL DIAGRAM (VARIABLE INTAKE SYSTEM)
NOTE:
A = Hardwired
OPERATION
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 EJB (engine junction box), and is connected to ground through the ECM (engine control module). To close the flap valves, the ECM (engine control module) 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 ECM (engine control module) 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
