Method and apparatus for determining a temperature of an emission catalyst

A method for determining a temperature of an emission catalyst communicating with exhaust gases from an engine, said method comprising:

• determining a first exhaust flow rate and a second exhaust flow rate based on a total flow rate of said exhaust gases;
• determining a first temperature of exhaust gases associated with said first exhaust flow rate based on a steady state temperature and an amount of heat transferred from said exhaust gases associated with said first exhaust flow rate to an exhaust system;
• determining a second temperature of exhaust gases associated with said second exhaust flow rate based on said steady state temperature;
• and
• determining said catalyst temperature based on said first temperature and said second temperature.

A method for determining a temperature of an exhaust flow comprising:

• measuring engine operating conditions including air mass;
• determining a steady state temperature as a function of the engine operating conditions;
• determining a first temperature of a first flow rate of an exhaust flow from an amount of heat transferred from said exhaust gases associated with said first exhaust flow rate to an exhaust system in response to air mass;
• determining a second temperature of a second flow rate of the exhaust flow bypassing a heat transfer model in response to the steady state temperature;
• and
• determining a first exhaust temperature from the first temperature and the second temperature as a function of air mass.