Resonance/Turbulence Intake System

On M52 TU, intake manifold is split into 2 groups of 3 runners which increases low end torque. Intake manifold also has separate internal turbulence bores which channels air from idle speed actuator directly to one intake valve of each cylinder. Routing the intake air to only one intake valve causes intake to swirl in cylinder. Together with high flow rate of intake air due to small intake cross sections, this results in a reduction in fluctuations and more stable combustion.

Resonance system provides increased engine torque at low RPM, as well as additional power at high RPM. Both of these features are obtained by using a resonance flap in intake manifold controlled by PCM. During low to mid range RPM, resonance flap is closed. This produces a long/single intake tube for velocity, which increases engine torque. During mid range to high RPM, resonance flap is open. This allows intake air to pull through both resonance tubes, providing air volume necessary for additional power at upper RPM range. When the flap is closed , this creates another dynamic effect. For example, as intake air is flowing into cylinder No. 1, intake valves will close. This creates a roadblock for inrushing air. The airflow will stop and expand back (resonance wave back pulse) with inrushing air to cylinder No. 5. The resonance wave, along with intake velocity, enhances cylinder filling. PCM controls a solenoid valve for resonance flap activation. At speeds below 3750 RPM, solenoid valve is energized and vacuum supplied from an accumulator closes resonance flap. This channels intake air through one resonance tube, but increases intake velocity. When engine speed is greater than 4100 RPM, solenoid is de-energized. Resonance flap is sprung open, allowing flow through both resonance tubes, increasing volume.