Patent ID: 6871490

Claim:
An emissions control system for a compression ignition engine capable of producing an exhaust gas stream to be treated by a reduction agent which is mixed with the exhaust gas stream to convert the exhaust gas stream prior to being directed into an SCR catalyst capable of reducing NOx in the exhaust gas stream, the system comprising: a sensor for determining the temperature of the exhaust gas stream prior to being mixed with the reduction agent; an exhaust gas recirculation valve associated with the compression ignition engine for directing the exhaust gas stream back into the compression ignition engine; a bypass valve associated with the compression ignition engine for directing the exhaust gas stream past the SCR catalyst; and an electronic control unit connected to the sensor, the bypass valve and the exhaust gas recirculation valve for determining whether the temperature of the exhaust gas stream is at a predetermined temperature and if so for controlling operation of the valve to allow a portion of the exhaust gas stream to be directed into the SCR catalyst, and if the temperature is below the predetermined temperature for controlling operation of the valves to direct all of the exhaust gas stream to avoid the SCR catalyst.