Low-cost evacuator for an engine having tuned Venturi gaps

A method of tuning a multi-Venturi gap Venturi device that generates vacuum, the method comprising:

• providing a test Venturi device having a first suction piece that defines a first suction port and having a body that defines a passageway comprising a first tapering portion having an inlet end and an outlet end and a second tapering portion having an inlet end and an outlet end, wherein the outlet end of the first tapering portion and the inlet end of the second tapering portion are spaced apart a lineal distance to define a first Venturi gap, wherein a plurality of additional Venturi gaps segment the second tapering portion and each of the additional Venturi gaps define a lineal distance between a first opening and second opening thereof, and wherein the first tapering portion converges toward the first Venturi gap and the second tapering portion diverges away from the first Venturi gap;
• operating the Venturi device as an aspirator and determining at which of the first Venturi gap and plurality of additional Venturi gaps is a location of minimum pressure for a first pre-selected operating condition;
• operating the Venturi device as an ejector and determining at which of the first Venturi gap and plurality of additional Venturi gaps is a location of minimum pressure for a second pre-selected operating condition;
• tuning whichever Venturi gap is at the location of minimum pressure as an aspirator to have higher vacuum suction by forming a first tuned Venturi gap having a smaller lineal distance than the same Venturi gap of the test Venturi device;
• and
• tuning whichever Venturi gap is at the location of minimum pressure as an ejector to have a higher suction flow rate by forming a second tuned Venturi gap having a larger lineal distance than the same Venturi gap of the test Venturi device;
• wherein the first tuned Venturi gap is not the same as the second tuned Venturi gap.