Two-stroke engine assembly having a catalytic converter and method for controlling same

A two-stroke engine assembly comprising:

• a two-stroke internal combustion engine (ICE);
• an exhaust system fluidly connected to the ICE, the exhaust system comprising:
• a tuned pipe fluidly connected to the ICE, the tuned pipe having:
• a diverging portion defining an inlet of the tuned pipe;
• a converging portion defining an outlet of the tuned pipe;
• and
• a central portion disposed between the diverging portion and the converging portion;
• a first catalytic converter fluidly connected to the tuned pipe;
• a second catalytic converter;
• a bypass passage fluidly connecting the tuned pipe to the second catalytic converter;
• a valve for opening and closing the bypass passage,
• in response to the valve being closed, exhaust gas flowing through the tuned pipe and the first catalytic converter,
• in response to the valve being opened, at least a portion of exhaust gas flowing from the tuned pipe, through the bypass passage, and through the second catalytic converter thereby bypassing the first catalytic converter;
• and
• a temperature sensor for sensing one of:
• a temperature of the first catalytic converter;
• and
• a temperature of exhaust gases exiting the first catalytic converter;
• and
• an electronic control unit (ECU) electronically connected to the ICE for controlling the ICE, the valve for controlling a position of the valve, and the temperature sensor for receiving a temperature signal indicative of a temperature of the first catalytic converter,
• in response to the temperature signal being indicative of the temperature of the first catalytic converter being above a predetermined temperature, the ECU controlling the valve to be opened.

A method for controlling a two-stroke engine assembly, the two-stroke engine assembly comprising a two-stroke internal combustion engine (ICE);

• and an exhaust system fluidly connected to the ICE, the exhaust system comprising a tuned-pipe, a first catalytic converter, a second catalytic converter, a first bypass passage fluidly connecting the tuned pipe to the second catalytic converter, a first valve for opening and closing the first bypass passage, a second bypass passage fluidly connected to the tuned pipe, and a second valve for opening and closing the second bypass passage, the method comprising:
• sensing, with a first temperature sensor, one of:
• a temperature of the first catalytic converter;
• and
• a temperature of exhaust gases exiting the first catalytic converter;
• comparing, by an engine control unit (ECU), the sensed temperature to a predetermined temperature;
• in response to the temperature sensed by the temperature sensor being above the predetermined temperature, the ECU controlling the first valve to be opened such that at least a portion of exhaust gas flowing in the tuned pipe flows through the first bypass passage, and through the second catalytic converter thereby bypassing the first catalytic converter;
• sensing, with a second temperature sensor, one of:
• a temperature of the second catalytic converter;
• and
• a temperature of exhaust gases exiting the second catalytic converter;
• comparing, by the ECU, the sensed temperature to a second predetermined temperature;
• and
• in response to the temperature sensed by the second temperature sensor being above the second predetermined temperature, the ECU controlling the second valve to be opened such that at least a portion of exhaust gas flowing in the tuned pipe flows through the second bypass passage thereby bypassing the first and second catalytic converters.