Variable Induction System: Description and Operation

Variable Inertia Charging System (VICS):

PURPOSE
The Variable Inertia Charging System (VICS) changes the effective length of intake manifold runners, taking advantage of high and low pressure oscillations to improve volumetric efficiency at different engine speeds.

LOCATION
Shutter valves are in dynamic chamber.

OPERATION
Opening and closing of the intake valves causes areas of high and low pressure to oscillate through the intake manifold at different harmonic frequencies, depending on engine speed. VICS changes the effective length of intake manifold runners, taking advantage of these oscillations to improve volumetric efficiency at different engine speeds. At low and mid-range engine speeds, oscillation frequency is low and shutter valves are closed. Intake air takes a longer path to the cylinders. At high speeds, oscillation frequency is higher. Shutter valves open and intake air takes a shorter path through the manifold. This synchronizes intake valve opening with the occurance of a high pressure area behind each valve. When an intake valve opens, high pressure air rushes into the cylinder followed by high velocity air from the intake runner. This "packs" cylinders with air/fuel mixture, producing more torque across a broader rpm range.

When engine speed is below 5100 rpm, manifold vacuum is applied to the diaphragm, holding shutter valves closed. When engine speed exceeds 5100 rpm, the PCME de-energizes the vacuum solenoid valve. The manifold vacuum port is blocked and the shutter valve diaphragm is vented to atmosphere. The diaphragm spring extends, opening the shutter valves.

CONSTRUCTION
VICS consists of a spring loaded vacuum diaphragm, four plate valves on a common shaft (one for each cylinder, similar to throttle valves), a vacuum chamber/reservoir with built-in one way check valve, and a computer operated vacuum solenoid valve.