Systems and methods for a split exhaust engine system

Abstract

Methods and systems are provided for operating a split exhaust engine system that provides blowthrough air and exhaust gas recirculation to an intake passage via a first exhaust manifold and exhaust gas to an exhaust passage via a second exhaust manifold. In one example, during a cold start, a method may include adjusting a position of a first valve disposed in an exhaust gas recirculation (EGR) passage based on an engine operating condition, the EGR passage coupled between the first exhaust manifold coupled to a first set of exhaust valves and the intake passage, upstream of a compressor. As one example, the engine operating condition may include an engine temperature or a temperature of a catalyst disposed in the exhaust passage.

1 . A method for an engine, comprising:
 during a cold start, adjusting a position of a first valve disposed in an exhaust gas recirculation (EGR) passage based on an engine operating condition, the EGR passage coupled between a first exhaust manifold coupled to a first set of exhaust valves and an intake passage, upstream of a compressor, while flowing a portion of exhaust gases to an exhaust passage including a turbine and an emissions control device via a second set of exhaust valves; and   adjusting an amount of fuel injected to the engine in response to an output of a first oxygen sensor positioned in the exhaust passage upstream of the emissions control device.   
     
     
         2 . The method of  claim 1 , wherein the emissions control device is arranged downstream of the turbine in the exhaust passage and further comprising supplying air to the exhaust passage at a location downstream of the emissions control device via the first exhaust manifold, the air not having participated in combustion in the engine. 
     
     
         3 . The method of  claim 2 , further comprising adjusting the amount of fuel injected to the engine in further response to output of a second oxygen sensor positioned downstream of the emissions control device. 
     
     
         4 . The method of  claim 2 , where the air is supplied in response to engine air flow being greater than a threshold, and further comprising:
 richening an air-fuel ratio of the engine and supplying the air to the exhaust passage before exhaust gases produced via the richened air-fuel ratio reach the location downstream of the emissions control device; and   ceasing to supply the air to the exhaust passage before leaning the air-fuel ratio.   
     
     
         5 . The method of  claim 1 , wherein the engine operating condition includes an engine temperature. 
     
     
         6 . The method of  claim 1 , wherein the engine operating condition includes a temperature of the emission control device, the emissions control device being a catalyst disposed in the exhaust passage, downstream of the turbine. 
     
     
         7 . The method of  claim 1 , further comprising opening the first valve disposed in the EGR passage at a start of engine cranking in response to the first set of exhaust valves being activated at the start of engine cranking and after firing a first cylinder, modulating the position of the first valve disposed in the EGR passage between an open and closed position based on a desired EGR flow amount and a pressure in the first exhaust manifold. 
     
     
         8 . The method of  claim 7 , further comprising closing the first valve disposed in the EGR passage in response to the pressure in the first exhaust manifold being lower than a threshold pressure. 
     
     
         9 . The method of  claim 8 , further comprising opening a second valve disposed in a bypass passage coupled between the first exhaust manifold and the exhaust passage, downstream of the turbine and the emissions control device, and further comprising supplying air to the exhaust passage via the bypass passage, the air not having participated in combustion in the engine. 
     
     
         10 . The method of  claim 1 , further comprising, in response to an oil pressure reaching a threshold pressure for adjusting an activation state of the first set of exhaust valves, switching the activation state of the first set of exhaust valves. 
     
     
         11 . The method of  claim 10 , further comprising, in response to switching the activation state from activated to deactivated, closing the first valve disposed in the EGR passage and in response to switching the activation state from deactivated to activated, modulating the position of the first valve disposed in the EGR passage between open and closed based on a desired EGR flow amount. 
     
     
         12 . The method of  claim 1 , further comprising, in response to an oil pressure reaching a threshold pressure for adjusting an activation state and timing profile of the first set of exhaust valves, adjusting a timing of the first set of exhaust valves. 
     
     
         13 . The method of  claim 1 , wherein the second set of exhaust valves are coupled exclusively to a second exhaust manifold, the second exhaust manifold separate from the first exhaust manifold. 
     
     
         14 . A method, comprising:
 during a cold start:
 adjusting a position of a first valve in an exhaust gas recirculation (EGR) passage to adjust flow from a first exhaust manifold exclusively coupled to a first set of exhaust valves to an intake passage upstream of a compressor based on an initial activation state of the first set of exhaust valves, while flowing a portion of exhaust gases to an exhaust passage including a turbine and an emissions control device via a second exhaust manifold exclusively coupled to a second set of exhaust valves; and 
   in a first mode, supplying an amount of air to the exhaust passage at a location downstream of the emissions control device via the first exhaust manifold, the amount of air supplied adjusted in response to an output of an oxygen sensor.   
     
     
         15 . The method of  claim 14 , further comprising, in a second mode, adjusting an amount of fuel injected to an engine in response to the output of the oxygen sensor without supplying air to the exhaust passage. 
     
     
         16 . The method of  claim 14 , wherein adjusting the position of the first valve is further based on a desired EGR flow and catalyst temperature during the cold start and wherein the initial activation state is at a start of engine cranking, before an oil pressure reaches a threshold oil pressure for adjusting the first set of exhaust valves. 
     
     
         17 . The method of  claim 14 , further comprising, in response to the initial activation state of the first set of exhaust valves being deactivated, advancing an intake valve closing timing of intake valves and retarding an exhaust valve opening timing of the second set of exhaust valves. 
     
     
         18 . A system for an engine, comprising:
 a first set of exhaust valves exclusively coupled to a first exhaust manifold;   a second set of exhaust valves exclusively coupled to a second exhaust manifold coupled to an exhaust passage including turbocharger turbine and a first catalyst and a second catalyst, the second catalyst located downstream of the first catalyst;   an exhaust gas recirculation (EGR) passage coupled between the first exhaust manifold and an intake passage, upstream of a turbocharger compressor, the EGR passage including an EGR valve;   a bypass pipe coupling the first exhaust manifold to the exhaust passage at a location between the first catalyst and the second catalyst; and   a controller including memory with computer-readable instructions for:
 adjusting a position of the EGR valve during a cold start based on an activation state of the first set of exhaust valves before a start of engine cranking; and 
 supplying air, not having participated in combustion to the exhaust passage at a location downstream of the first catalyst and upstream of the second catalyst via the bypass pipe. 
   
     
     
         19 . The system of  claim 18 , wherein the computer-readable instructions further include instructions for switching the activation state of the first set of exhaust valves in response to an oil temperature reaching a threshold temperature and closing the EGR valve. 
     
     
         20 . The system of  claim 18 , further comprising additional instructions to adjust fuel supplied to the engine in response to an output of an oxygen sensor positioned in the exhaust passage downstream of the first catalyst.