Resonance Intake Manifold: Notes

Intake manifold length is crucial to engine torque and power output. When the intake valves open a considerable momentum is developed. Backpressure created when intake valves close begins to expand in the opposite direction. The level of pressure is dependent on airflow velocity and gas quantity mass present in intake manifold.

If mixture column is quickly accelerated or braked, oscillation occurs. Oscillation frequency is dependent on intake manifold length. If engine timing and mixture column oscillations match, then a certain charge effect is attained by means of resonance oscillation. Since mixture column oscillations are also engine speed dependent, resonance oscillations at a set intake manifold length can only be attained in a particular engine speed range. To make the charge effect available over a broader engine RPM range, a resonance flap is used which effectively makes 2 different intake manifold lengths available.