Variable Induction Control Valve: Description and Operation

Variable Resonance Induction System (VRIS):

The shutter valve, located at the inlet to the dynamic chamber from the throttle body, is part of the "Variable Resonance Induction System" (VRIS). The shutter valve is used to improve engine performance across a wider operating range by varying the dynamic chamber effective volume at different engine speeds and loads.

At different engine speeds, areas of high and low pressure oscillate through the intake manifold at different harmonic frequencies, due to the opening and closing of the intake valves. The VRIS takes advantage of this by changing the effective volume of the dynamic chamber of the intake manifold, thereby changing the frequency of the oscillations. This helps synchronize the occurance of a high pressure area at the valves with the valve timing, while air inside the intake runners still has momentum and velocity towards 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. When the dynamic chamber volume is large, air in the manifold oscillates at a low frequency. This helps improve volumetric efficiency at low rpm, and corresponds to the shutter valve being open. When the dynamic chamber volume is small, the air oscillates at a higher frequency. This is effective at high rpm, and corresponds to the shutter valve being closed.

The "VRIS" system consists of the shutter valve, vacuum diaphragm actuator, computer controlled vacuum solenoid valve, vacuum chamber (reservoir) and one way vacuum check valve. Vacuum is "stored" in the vacuum chamber by a one-way check valve (in line between the source and the reservoir), and applied to the diaphragm through a computer operated vacuum solenoid valve. The computer monitors engine sensors to determine engine speed and load, then energizes the vacuum solenoid when shutter valve operation is required.