The multi-ram system functional diagram shows four stages of air flow:

Figure 1:	Intake Air Assembly
Figure 2:	Multi-Ram System Functional Diagram

•	I is air flow at idle

The characteristic torque curve of a normally aspirated engine depends mainly on how the engines average pressure changes over the RPM band. The average pressure is proportional to the volume of the air mass present in the cylinder when the inlet valve is closed. The design of the inlet system determines how large an air mass can be sucked into a cylinder at a given engine RPM.

Thus, the air intake system determines the engines torque curve. A longer intake manifold results in higher torque at lower RPM, and a shorter intake manifold results in higher torque at higher RPM.

The intake manifold on this engine is fitted with 2 valves which can be set for 4 different intake manifold lengths. The 4 different manifold lengths obtainable result in different torque curves with maximum torque at different engine RPM. The intake plenum switchover valve (1) is located in the intake manifold between the cylinder heads. The intake resonance switchover valve (2) is located between the 2 resonating pipes connected to the intake manifold. The control module controls the 2 valves by means of solenoid valves and vacuum operated diaphragm units. The solenoid valves are supplied with current via the main relay and are grounded by the control module. When the control module enables the solenoid for the intake plenum swithchover valve, the valve opens and connects the inlet systems of the two banks of cylinders to each other. When the control module enables the solenoid for the intake resonance switchover valve, the valve opens a connection between the 2 resonating pipes and the active length of the pipes are thus reduced.

During wide-open throttle (WOT) acceleration from low RPM, the control module disables the intake plenum switchover valve. This separates the cylinder banks from each other and connects each of them to its own resonating pipe. With the intake resonance switchover valve now closed, the full length of the resonating pipes is utilized.

When the engine speed reaches 3,200 RPM, the control module enables the solenoid for the intake resonance switchover valve. This causes the valve to open and connect 2 resonating pipes, so their active length is reduced.

When engine speed reaches 4,100 RPM, the control module enables the circuit to the intake plenum switchover valve, so that the 2 inlet systems, 1 for each bank of cylinders, are connected to each other, and the effective pipe length is the shortest possible.

Using this system allows the torque curves to overlap in a way that produces the most favorable results.

At speeds below 4,100 RPM and with a throttle valve angle less than 50 percent, the intake plenum switchover valve is always open. This keeps the idle air control (IAC) valves supplementary air distributed equally between the cylinders.