Variable Induction Control Actuator: Description and Operation

CONTROL OF VARIABLE INTAKE SYSTEM

The ICM operates the variable intake system, which consists of:
^ two manifold pipes (1 and 2) of different lengths and diameters, arranged in parallel. The configuration is optimized for maximum volumetric efficiency at different engine loads and speeds;
^ a vacuum actuator (3) which opens and closes the damper in the shorter intake pipes (2);
^ a solenoid valve (8/14) which opens and closes the vacuum line from the engine. The valve is, in turn, operated by the ICM in response to the prevailing engine speed and throttle opening signals;
^ a vacuum reservoir (4);
^ a non-return valve (5) installed in the vacuum line to the manifold.

Under normal driving conditions, the solenoid valve is not activated by the ICM. The connection between the vacuum reservoir and servo is closed, and the servo spring exerts an upward force on the pushrod, opening the dampers in the short pipes through the linkage.

The ICM activates the solenoid valve at speeds between 1800 and 4200 rpm, if the throttle is simultaneously open by more than approx. 80%. The connection between the vacuum reservoir and servo is opened, and the vacuum overcomes the servo spring force, pulling the diaphragm push rod downward and closing the dampers.

The solenoid valve is not activated at speeds below 1800 rpm or over 4200 rpm and the dampers remain open regardless of the throttle position.

In the event of an electrical or vacuum system fault, the dampers remain fully open and maximum power is maintained at the expense of low-speed torque