Internal combustion engine having two fuel injectors per cylinder and control method therefor

1. A method for controlling a two-stroke internal combustion engine, the engine having at least one combustion chamber, at least one direct fuel injector for injecting fuel directly in the at least one combustion chamber, at least one port fuel injector for injecting fuel upstream of the at least one combustion chamber, and at least one exhaust valve movable between at least a fully lowered position and a fully opened position, the method comprising:

supplying a first fuel quantity to the at least one combustion chamber, a first ratio of the first fuel quantity being supplied by the at least one port fuel injector, the first ratio being greater than or equal to zero; and

supplying a second fuel quantity to the at least one combustion chamber when a position of the at least one exhaust valve changes, a second ratio of the second fuel quantity being supplied by the at least one port fuel injector, the second ratio being greater than or equal to zero, and the second ratio being different from the first ratio.

2. The method of claim 1 , wherein when the position of the at least one exhaust valve changes to increase an opening of the at least one exhaust valve, the second ratio is greater than the first ratio.

3. The method of claim 1 , wherein when the position of the at least one exhaust valve changes to increase an opening of the at least one exhaust valve, the second ratio is smaller than the first ratio.

4. The method of claim 1 , wherein:

at a first engine speed, for an increase of throttle position from a first throttle position to a second throttle position, with the at least one exhaust valve opening from a first exhaust valve position to a second exhaust valve position, the second ratio is greater than the first ratio;

at a second engine speed, for an increase of throttle position from a third throttle position to a fourth throttle position, with the at least one exhaust valve opening from a third exhaust valve position to a fourth exhaust valve position, the second ratio is smaller than the first ratio; and

a difference in opening between the second and first throttle valve positions is equal to a difference in opening between the fourth and third throttle valve position.

5. The method of claim 4 , wherein the second engine speed is greater than the first engine speed.

6. The method of claim 5 , wherein the third throttle valve position is a more open throttle valve position than the second throttle valve position.

7. The method of claim 4 , wherein the first exhaust valve position is a fully lowered position, the second exhaust valve position is a first intermediate position, the third exhaust valve position is a second intermediate position, and the fourth exhaust valve position is a fully opened position.

8. The method of claim 1 , wherein when the position of the at least one exhaust valve changes from a fully lowered position to another exhaust valve position, the second ratio is greater than the first ratio.

9. The method of claim 8 , wherein when the position of the at least one exhaust valve changes from an intermediate position to a fully opened position, the second ratio is smaller than the first ratio.

10. The method of claim 1 , wherein:

the second fuel quantity is supplied when the position of the at least one exhaust valve changes from a fully lowered position to a first intermediate position;

the second ratio is greater than the first ratio;

the method further comprises supplying a third fuel quantity to the at least one combustion chamber when the position of the at least one exhaust valve changes from a second intermediate position to a fully open, a third ratio of the third fuel quantity being supplied by the at least one port fuel injector, the third ratio being greater than the first ratio and smaller than the second ratio.