Methods and systems for exhaust gas heat recovery

A method for an engine, comprising:

• during a first condition, before light-off of an exhaust catalyst and before a coolant temperature reaches a threshold coolant temperature, increasing exhaust flow from a first exhaust valve to the exhaust catalyst while decreasing exhaust flow from a second exhaust valve to a heat exchanger;
• during a second condition, after light-off of the exhaust catalyst and before the coolant temperature reaches the threshold coolant temperature, increasing exhaust flow from the second exhaust valve to the heat exchanger while decreasing exhaust flow from the first exhaust valve to the exhaust catalyst;
• and
• during a third condition, after light-off and when the coolant temperature reaches or increases above the threshold coolant temperature, directing a portion of exhaust flow to the exhaust catalyst bypassing the heat exchanger while directing a remaining portion of exhaust flow to the heat exchanger, a ratio of the portion of exhaust flow to the remaining portion of exhaust flow based on a desired EGR flow and cabin heating demand.

A system comprising:

• an engine cylinder having a first exhaust valve and a second exhaust valve;
• a first exhaust manifold coupling the first exhaust valve to a first exhaust passage, the first passage directly coupled to a common exhaust passage including an exhaust catalyst;
• a second exhaust manifold coupling the second exhaust valve to a second separate exhaust passage;
• a heat exchanger located within the second exhaust passage;
• an EGR valve located within the second exhaust passage downstream of the heat exchanger;
• a return passage coupling the EGR valve to the common exhaust passage at a location upstream of the exhaust catalyst;
• and
• a controller with computer readable instructions for:
• responsive to a temperature of the exhaust catalyst below a light-off temperature, delivering exhaust gases from the cylinder to the exhaust catalyst via the first exhaust valve and the first exhaust manifold bypassing the heat exchanger;
• and
• responsive to the temperature reaching or increasing above the light-off temperature, if an engine coolant temperature is below a threshold, delivering exhaust gases from the cylinder to the heat exchanger via the second exhaust valve and the second exhaust manifold;
• otherwise, delivering a portion of exhaust gases from the cylinder to the exhaust catalyst via the first exhaust valve and delivering a remaining portion of exhaust gases from the cylinder to the heat exchanger via the second exhaust valve.