Variable Induction System: Description and Operation

DESCRIPTION AND OPERATION
The air induction system supplies filtered air to the engine to mix with the fuel for combustion. It consists of:

Air cleaner assembly
Mass air flow (MAF) sensor
Throttle body
Intake manifold
Bypass air control valve (B6 DOHC)

The mass air flow (MAF) sensor is used to measure the volume of air passing into the engine. The throttle body controls air quantity and includes:

Throttle position (TP) sensor
Bypass air control valve (B6 DOHC)

The idle air control system supplies small quantities of air during engine idle by bypassing air around the throttle body. This system consists of the idle air control valve and air valve The throttle position (TP) sensor detects the throttle opening and provides the ECM with this information. The air valve supplies idle air when the engine is cold for cold-start idle-up. A Variable Inertia Charging System (VICS) has been incorporated into the air intake system of the B6 DOHC engine. The system uses resonance waves built up in the intake manifold when the intake valves abruptly close off the high velocity air stream. The resonance waves travel back up the intake runners into the dynamic chamber and provides additional velocity to the air entering the next cylinder. As the engine speed reaches 4,750 rpm, the shutter valves are opened to increase the length of the resonance path. This changes the effective length of the intake runners and alters the torque characteristics of the engine. The result is an increase in engine torque and a wider torque band.