Variable Induction System: Description and Operation

Multi-Ram System:

DESCRIPTION
The Catera Multi-Ram System uses variable air induction tuning in order to achieve maximum performance and efficiency over the entire operating range of the engine. The system consists of two main parts. The intake manifold contains the Intake Plenum Switchover valve. This vacuum operated valve is essentially a moveable divider that changes the airflow characteristics of the intake manifold. Vacuum to the valve is controlled by an ECM controlled solenoid valve. The second part is the Intake Resonance Switchover valve. This vacuum operated valve is located in the air intake duct assembly in front of the engine. This is also basically a moveable divider that changes the tuning of the air intake system. Vacuum to the valve is controlled by an ECM controlled solenoid valve. By opening and closing these valves independently, in different combinations, four different air flow configurations can be created, each optimized to a particular set of engine operating conditions.

OPERATION
Both solenoid valves are supplied power via the Main relay (Switched B+). Both solenoid valves have a control circuit to the ECM. The ECM controls a valve by grounding the control circuit via an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled.

Each driver has a fault line which is monitored by the ECM. When the ECM is commanding a component on, the voltage of the control circuit should be low (near 0 volts). When the ECM is commanding the control circuit to a component off, the voltage potential of the circuit should be high (near the battery voltage). If a problem is detected with either of the solenoid valve control circuits, a DTC will set.

Air Flow Stages
The Multi-Ram System functional Diagram shows four stages of air flow: I is Air flow at idle; II is Air flow at full load, low RPM; III is Air flow at full load, mid RPM; IV is Air flow at full load, high RPM.