Engine control system having quick-open valve timing

1. A method for operating a two-stroke engine having a cylinder, a piston disposed in sliding engagement with the cylinder, and an exhaust valve configured to open and close an exhaust port, the method comprising:

directing air and a fuel into the cylinder;

burning a mixture of the air and the fuel to force the piston between a top dead center (TDC) position and a bottom dead center (BDC) position;

cyclically opening and closing the exhaust valve according to a first valve timing during movement of the piston relative to the cylinder;

receiving a signal that is indicative of a condition associated with pre-ignition of the mixture of the air and the fuel, the condition associated with pre-ignition of the mixture of the air and the fuel includes at least one of an inlet air temperature above a predetermined temperature threshold and an engine load above a predetermined load threshold; and

selectively opening and closing the exhaust valve according to a second valve timing, based at least on the signal,

wherein a crank angle duration to move the exhaust valve from a closed position to a maximum lift position according to the second valve timing is less than a crank angle duration to move the exhaust valve from the closed position to the maximum lift position according to the first valve timing, and

wherein a total crank angle duration of the exhaust valve being open according to the second valve timing is equal to a total crank angle duration of the exhaust valve being open according to the first valve timing.

2. The method of claim 1 , wherein opening the exhaust valve in the second valve timing includes opening the exhaust valve to 50% of the maximum lift position when the piston is 35-37° past TDC.

3. The method of claim 2 , wherein opening the exhaust valve in the second valve timing further includes opening the exhaust valve to the maximum lift position when the piston is 63-65° past TDC.

4. The method of claim 3 , wherein closing the exhaust valve in the second valve timing includes lowering the exhaust valve to 75% of the maximum lift position when the piston is 99-101° past TDC.

5. The method of claim 4 , wherein closing the exhaust valve in the second valve timing further includes lowering the exhaust valve to 25% of the maximum lift position when the piston is 126-128° past TDC.

6. The method of claim 1 , wherein opening the exhaust valve in the second valve timing includes moving the exhaust valve from the closed position to the maximum lift position in 41% of the total crank angle duration of the exhaust valve being open according to the second valve timing.

7. The method of claim 1 , wherein directing the air and the fuel into the cylinder includes radially injecting gaseous fuel into the cylinder through an intake port.

8. The method of claim 1 , further comprising changing a rotational speed of a cam arrangement to selectively open and close the exhaust valve according to the second valve timing.

9. The method of claim 3 , wherein opening the exhaust valve in the first valve timing includes opening the exhaust valve to the maximum lift position at 84-86° past TDC.

10. The method of claim 9 , wherein opening the exhaust valve in the first valve timing further includes moving the exhaust valve from the closed position to the maximum lift position in 54% of the total crank angle duration of the exhaust valve being open according to the first valve timing.

11. The method of claim 1 , further comprising selectively delaying closing of the exhaust valve in the second valve timing.

12. A control system for a two-stroke engine including a cylinder, a piston disposed in sliding engagement with in the cylinder, and an exhaust valve, the control system comprising:

a variable valve timing device configured to selectively adjust opening and closing of the exhaust valve;

a sensor configured to generate a signal that is indicative of a condition associated with pre-ignition of a mixture of air and a fuel in the cylinder; and

a controller in communication with the variable valve timing device and the sensor, the controller being configured to control the variable valve timing device to selectively initiate a conventional valve timing or a quick-open valve timing based on the signal,

wherein a crank angle duration to move the exhaust valve from a closed position to a maximum lift position according to the quick-open valve timing is less than a crank angle duration to move the exhaust valve from the closed position to the maximum lift position according to the conventional valve timing,

wherein a total crank angle duration of the exhaust valve being open according to the quick-open valve timing is equal to a total crank angle duration of the exhaust valve being open according to the conventional valve timing,

wherein the sensor includes at least one of a temperature sensor and a load sensor, and

wherein the condition associated with pre-ignition of the mixture of the air and the fuel includes at least one of an inlet air temperature above a predetermined temperature threshold and an engine load above a predetermined load threshold.

13. The control system of claim 12 , wherein according to the quick-open valve timing the exhaust valve is moved from the closed position to the maximum lift position in 41% of the total crank angle duration of the exhaust valve being open according to the quick-open valve timing.