System for continuous control of air-fuel ratio with ionization current

A control system of carburation of a two-stroke internal combustion engine comprising:

• a. operating the engine with an air/fuel ratio of a predetermined initial value (λ0);
• b. for the initial value (λ0) of the air/fuel ratio, constructing a first curve (ci(α)) representing an ionization current (ci) as a function of the angular position (α) of a crankshaft of the engine, the ionization current (ci) being measured through spark plug electrodes;
• c. calculating a value (z0) equal to an integral of the first curve (ci(α)) in a predetermined angular interval of the crankshaft;
• d. interrupting fuel supply for a few engine cycles, thereby increasing the air/fuel ratio of the engine to a second value (λ1) larger than the initial value (λ0), the second value (λ1) of the air/fuel ratio being equal to the sum of the initial value (λ0) and a predetermined quantity (Δλ), the predetermined quantity (Δλ) being smaller than or equal to 0.05;
• e. for the second value (λ1) of the air/fuel ratio, constructing a second curve (ci(α)) representing the ionization current (ci) as a function of the angular position (α) of the crankshaft, the ionization current (ci) being measured through the spark plug electrodes;
• f. calculating a value (z1) equal to an integral of the second curve (ci(α)) in a predetermined angular interval of the crankshaft that is equal to the preceding angular interval;
• g. calculating a difference (Δz) as the value (z1) of the integral of the second curve minus the value (z0) of the integral of the first curve;
• h. if the difference (Δz) has an absolute value greater than a predetermined threshold value (Δzrif), intervening on the carburation to regulate a quantity of fuel injected, wherein the regulating of the quantity of fuel injected includes increasing the quantity of fuel injected in a case of a negative difference and reducing the quantity of fuel injected in a case of a positive difference, wherein the system provides a continuous and automatic intervention during an entire operating period of the engine and not only when operated at wide open throttle.