TWO-STROKE ENGINE ASSEMBLY HAVING A CATALYTIC CONVERTER AND METHOD FOR CONTROLLING SAME
A method for controlling a two-stroke engine assembly having a two-stroke internal combustion engine (ICE) having first and second cylinders; and an exhaust system fluidly. The exhaust system has a tuned pipe and a catalytic converter. The method having the steps of: sensing in the exhaust system, with a lambda sensor, a first combustion air-fuel equivalence ratio (λ) and a second combustion λ, the first and second combustion λ's being subsequent combustion λ's of different ones of the first and second cylinders; determining, by an engine control unit (ECU), a difference between the first and second combustion λ's; and in response to the difference between the first and second combustion λ's being greater than a predetermined λ, modifying an air-fuel ratio in at least one of the first and second cylinders to reduce the difference between the first and second combustion λ's below the predetermined λ.
1 . A method for controlling a two-stroke engine assembly, the two-stroke engine assembly comprising a two-stroke internal combustion engine (ICE) having first and second cylinders; and an exhaust system fluidly connected to the ICE, the exhaust system comprising a tuned pipe and a catalytic converter; the method comprising:
sensing in the exhaust system, with a lambda sensor, a first combustion air-fuel equivalence ratio (λ) and a second combustion λ, the first combustion λ and the second combustion λ being subsequent combustion λ's of different ones of the first and second cylinders;
determining, by an engine control unit (ECU), a difference between the first combustion λ and the second combustion λ; and
in response to the difference between the first combustion λ and the second combustion λ being greater than a predetermined λ, modifying an air-fuel ratio in at least one of the first and second cylinders to reduce the difference between the first combustion λ and the second combustion λ below the predetermined λ.
2 . The method of claim 1 , wherein:
the predetermined λ is a first predetermined λ; and
in response to the difference between the first combustion λ and the second combustion λ being less than the first predetermined λ:
sensing with the lambda sensor a current λ in the exhaust system over a first period of time;
determining, by the ECU, a difference between an average value X of the current λ over the first period of time to a desired λ; and
in response to the difference between the average value X and the desired λ being greater than a second predetermined λ, modifying the air-fuel ratio in both of the first and second cylinders to reduce the difference between the average value X and the desired λ.
3 . The method of claim 2 , wherein the desired λ corresponds to a λ for operating the catalytic converter of the exhaust system.
4 . The method of claim 1 , wherein modifying the air-fuel ratio in at least one of the first and second cylinders to reduce the difference between the first combustion λ and the second combustion λ below the predetermined λ comprises:
modifying the air-fuel ratio in the first cylinder;
sensing with the lambda sensor the first combustion λ and the second combustion λ after modifying the air-fuel ratio in the first cylinder;
determining, by the ECU, the difference between the first combustion λ and the second combustion λ after modifying the air-fuel ratio in the first cylinder;
in response to the difference between the first combustion λ and the second combustion λ after modifying the air-fuel ratio in the first cylinder being less than the difference between the first combustion λ and the second combustion λ prior to modifying the air-fuel ratio in the first cylinder:
further modifying the air-fuel ratio in the first cylinder until the difference, determined by the ECU, between the first combustion λ and the second combustion λ sensed by the lambda sensor is less than the predetermined λ; and
in response to the difference between the first combustion λ and the second combustion λ after modifying the air-fuel ratio in the first cylinder being greater than the difference between the first combustion λ and the second combustion λ prior to modifying the air-fuel ratio in the first cylinder:
modifying the air-fuel ratio in the second cylinder until the difference, determined by the ECU, between the first combustion λ and the second combustion λ sensed by the lambda sensor is less than the predetermined λ.
5 . The method of claim 4 , wherein:
modifying the air-fuel ratio in the first cylinder comprises decreasing the air-fuel ratio in the first cylinder; and
modifying the air-fuel ratio in the second cylinder comprises decreasing the air-fuel ratio in the second cylinder.
6 . The method of claim 4 , wherein in response to the difference between the first combustion λ and the second combustion λ after modifying the air-fuel ratio in the first cylinder being greater than the difference between the first combustion λ and the second combustion λ prior to modifying the air-fuel ratio in the first cylinder:
further modifying the air-fuel ratio in the first cylinder to obtain an air-fuel ratio in the first cylinder corresponding to an air-fuel ratio present in the first cylinder prior to modifying the air-fuel ratio in the first cylinder.