Four stroke engine inlet duct - contains flexible hose to reduce duct cross:section at low engine speed by external pressurisation

摘要

The inlet duct, (4, 5) of a four-stroke combustion engine is provided with a resilient inner wall (6) over at least part of its length. By admitting pressure (via 10) to the outside of this wall, the free cross-sectional flow area of the duct can be varied at will or automatically, so as to reduce the area at low engine speed. The wall may be a flexible hose inside the duct. The hose may be pre-shaped with an indentation (7). The wall thickness of the indentation may be smaller than of the remainder of the hose. The pressure may be taken from a point (2) immediately upstream of the inlet valve (3).