Variable Induction Control Valve: Description and Operation

Variable Inertia Charging System:

Shutter Valves (VICS):

The shutter valve, located on the outlet of the dynamic chamber to the intake manifold, is part of the "Variable Inertia Charging System" (VICS). Due to the opening and closing of the intake valves, areas of high and low pressure oscillate through the intake manifold at different harmonic frequencies, depending on the engine speed. The VICS changes the effective length of the intake manifold runners, taking advantage of these oscilations to improve volumetric efficiency at different engine speeds. At low and mid-range engine speeds, when the frequency of the oscilations is low, the shutter valves are closed, forcing intake air to take the longer path to the cylinders. At high speeds, the frequency of the oscilations is much higher. The shutter valves open and the intake air can the the short path through the manifold. This helps synchronize the opening of the intake valves with the occurance of a high pressure area just behind each valve, while air inside the intake runners still has momentum and velocity toward the valves as they are opening. When an intake valve opens, high pressure air rushes into the cylinder followed by high velocity air from the intake runner, to help "pack" the cylinder with more air and fuel before the valve closes. This helps the engine produce more torque across a broader rpm range.

The VICS system 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.

When the engine speed is below 5,000 rpm, manifold vacuum is applied to the diaphragm, holding the shutter valves in the closed position. When the engine speed exceeds 5,000 rpm, the computer de-energized the vacuum solenoid valve. The manifold vacuum port is blocked and the shutter valve diaphragm is vented to the atmosphere. With vacuum no longer applied, the diaphragm spring extends, opening the shutter valves.