Control of exhaust gas stoichiometry with inducted secondary air flow

A method for operating a marine engine, comprising the steps of:

• providing a first valve disposed upstream from a first cylinder of said engine, said first valve being connected in fluid communication between said first cylinder and a source of air;
• providing a second valve disposed upstream from a second cylinder of said engine, said second valve being connected in fluid communication between said second cylinder and said source of air;
• providing a third valve disposed upstream from a third cylinder of said engine, said third valve being connected in fluid communication between said third cylinder and said source of air;
• providing a fourth valve disposed upstream from a fourth cylinder of said engine, said fourth valve being connected in fluid communication between said fourth cylinder and said source of air;
• providing a sensor disposed downstream from said first and second cylinders, said sensor providing an output signal which is representative of an exhaust gas characteristic;
• measuring said exhaust gas characteristic;
• and
• controlling a first magnitude of a first flow of air through said first valve, a second magnitude of a second flow of air through said second valve, a third flow of air through said third valve and a fourth magnitude of a fourth flow of air through said fourth valve in accordance with said exhaust gas characteristic and in accordance with a predetermined relationship among said first, second, third and fourth magnitudes.

A method for operating a marine engine, comprising the steps of:

• providing a first valve disposed upstream from a first cylinder of said engine, said first valve being connected in fluid communication between said first cylinder and a source of air;
• providing a second valve disposed upstream from a second cylinder of said engine, said second valve being connected in fluid communication between said second cylinder and said source of air;
• providing a third valve disposed upstream from a third cylinder of said engine, said third valve being connected in fluid communication between said third cylinder and said source of air;
• providing a fourth valve disposed upstream from a fourth cylinder of said engine, said fourth valve being connected in fluid communication between said fourth cylinder and said source of air;
• providing a oxygen sensor disposed downstream from said first and second cylinders, said oxygen sensor providing an output signal which is representative of an exhaust gas characteristic, said output signal having a first state which is representative of said air/fuel ratio being richer than stoichiometry and a second state which is representative of said air/fuel ratio being leaner than stoichiometry;
• measuring said exhaust gas characteristic;
• providing a carburetor upstream from said first and second valves, said carburetor being calibrated to provide an air/fuel ratio which is richer than a stoichiometric air/fuel ratio;
• and
• controlling a first magnitude of a first flow of air through said first valve, a second magnitude of a second flow of air through said second valve, a third flow of air through said third valve and a fourth magnitude of a fourth flow of air through said fourth valve in accordance with said exhaust gas characteristic and in accordance with a predetermined relationship among said first, second, third and fourth magnitudes.