Pulsation-dampening fuel trim strategy for air/fuel ratio control of propane-fueled, spark-ignited engines

A trim system for controlling an equivalence ratio of a fuel system and mitigating pressure pulsations in the fuel system, the fuel system including an air duct, the trim system comprising:

• a mixer disposed in the air duct, the mixer having a pressure port and an air valve vacuum port;
• a converter having an outlet port and a bias port, the outlet port operably coupled to the mixer to deliver vaporized fuel to the mixer;
• a balance line operably coupled to the pressure port, the bias port, and the air valve vacuum port, the balance line providing pressure to the bias port;
• first and second trim valves disposed in the balance line;
• and
• an electronic control module operably coupled to the first and second trim valves, the electronic control module controlling operation of the first and second trim valves such that the equivalence ratio is controlled and the pressure pulsations are mitigated.

A trim system for controlling an equivalence ratio for a spark-ignited internal-combustion engine comprising:

• an air duct extending between an air cleaner and the spark-ignited internal-combustion engine;
• a mixer disposed in the air duct, the mixer having a pressure port and an air valve vacuum port;
• a converter having an outlet port and a bias port, the outlet port operably coupled to the mixer to deliver vaporized fuel to the mixer;
• a balance line operably coupled to the pressure port, bias port, and the air valve vacuum port, the balance line providing pressure to the bias port;
• at least one orifice disposed in the balance line;
• first and second trim valves disposed in the balance line;
• and
• an electronic control module operably coupled to the first and second trim valves, the electronic control module controlling the operation of the first and second valves such that the equivalence ratio of the spark-ignited internal-combustion engine is controlled.