Intake Manifold: Description and Operation
Intake Air Distribution and Filtering - 3.2L
Intake Manifold
At low engine speeds, long intake tracts are functioned to provide optimum engine torque; shorter tracts are used at medium speeds, again to optimize engine torque for the existing engine speed range.
At higher engine speeds the benefits of optimizing the tract lengths are outweighed by necessity of maintaining an appropriate supply of air to meet the engine's requirements. Therefore, the plenum valve is opened to create a single, large plenum volume to provide the maximum quantity of air to charge the engine's cylinders.