System and method for controlling a cold light off catalyst

A method of controlling a vehicle powertrain having a normally aspirated engine, the powertrain having an advanced device positioned in an exhaust of the normally aspirated engine, a main catalyst positioned in the exhaust downstream of the advanced device, a cold light off catalyst (CLOC) positioned in a bypass passage around the advanced device, a CLOC valve that selectively routes exhaust flow from the normally aspirated engine between advanced device and the CLOC, and a controller, the method comprising:

• determining a temperature of a main catalyst;
• determining, based on a temperature of the main catalyst being less than a temperature threshold, a first engine torque request;
• commanding, based on the first engine torque request being less than a first torque threshold, the CLOC valve to operate in a CLOC mode;
• operating the CLOC valve in a normal mode based on a temperature of the main catalyst not being less than a temperature threshold, the normal mode corresponding to routing exhaust gas through the advanced device and to the main catalyst
• determining, based on the first engine torque request not being less than a first torque threshold, whether the torque request is greater than a second torque threshold;
• and
• commanding, based on the torque request being greater than the second torque threshold, the CLOC valve to operate in the normal mode.