Intake manifold having runners with variable cross sectional area

A slider assembly for a tunable engine manifold, comprising:

• a mounting member for mounting the assembly to an engine manifold, a set of sliders pivotally attached to the assembly, each slider forming one wall of a respective runners of the manifold such that rotational pivotal movement of the sliders alters the area of the runners, wherein each slider further comprises a seal to seal the slider with respect to the runner;
• a slider actuator connected to the sliders such that movement of the slider actuator pivots the sliders in the runners;
• and
• an actuator to move the slider actuator.

A tunable engine manifold for connecting to an internal combustion engine, comprising:

• a set of runners, each runner connecting to a port of a cylinder of the engine;
• a set of sliders, wherein each slider has a downstream end and is pivotally mounted at the downstream end within a respective one of the runners for rotational movement between a first position and a second position, such that movement of the slider about the pivot alters the cross sectional area of the runner and wherein when the slider is at the first position and when the slider is at the second position the respective one of the runners is substantially free of discontinuous changes in cross-sectional size at the downstream end of the slider;
• and
• a slide actuator being operable to pivot the sliders within the runners.