Inlet manifold control - KV6 engine (Manifold & exhaust systems) (page 2 of 2)

The KV6 engine is equipped with a 3 condition, 4 stage variable induction system to maximise volumetric efficiency and hence output at full load throughout the engine speed range. The induction system is a twin chamber design, with 2 motor operated butterfly valves between the chambers. The first valve, the connect valve, is just upstream of the throttle body, and the second, the balance valve, being at the end of the chambers. The fuel ECU uses the engine speed signal from the crank/cylinder sensor to control the position of the valves by operating the valve motors.

At engine speeds below 2700 rev/min, both the connect and balance valves are closed. This gives the dynamic effect of having 2 three cylinder engines, allowing the chambers to resonate with long secondary pipe lengths providing the first torque peak.

As engine speed increases to between 2700 and 3250 rev/min, the connect valve is opened, this shortens the secondary pipe resonator length providing a second torque peak at a higher engine speed.

To obtain peak torque at speeds above 3250 and below 4900 rev/min, both the connect and balance valves are opened. It is the use of primary pipe resonance, coupled with the resonance between the chambers connected by the balance valve that provides the third torque peak.

At speeds above 4900 rev/min both the connect and balance valves are closed, so the engine is once again exhibiting the dynamic behaviour of 2 three cylinder engines. Using the primary pipe length along with the secondary pipe length, peak power is provided.

The Variable Induction System also improves part load fuel consumption by reducing the pumping loss. Pumping loss is a function of manifold absolute pressure and exhaust back pressure. By closing both butterfly valves in the variable induction system at part load, the part load volumetric efficiency decreases, this requires the throttle to be opened more than it ordinarly would. This increases the manifold absolute pressure, thus reducing the pumping loss which gives an improvement in fuel consumption.