Method for determining a dilution of recirculated gases in a split exhaust engine

A method, comprising:

• flowing gases from a first set of exhaust valves to a compressor disposed in an intake passage and flowing exhaust gas from a second set of exhaust valves to a turbine disposed in an exhaust passage and not to the intake passage, where each cylinder of a plurality of engine cylinders includes one valve of the first set of exhaust valves and one valve of the second set of exhaust valves;
• determining a dilution rate of the gases flowing from the first set of exhaust valves to the compressor based on a temperature of each of:
• the gases flowing from the first set of exhaust valves to the compressor, before the gases enter the intake passage, intake air flowing in the intake passage, upstream of where the gases from the first set of exhaust valves enter the intake passage, and combined gases flowing through the intake passage, downstream of where the gases from the first set of exhaust valves enter the intake passage;
• and
• adjusting one or more of fuel injection to the plurality of engine cylinders and spark timing based on the determined dilution rate.

A system for an engine, comprising:

• a first set of exhaust valves exclusively coupled to a first exhaust manifold, the first exhaust manifold coupled to an intake passage, upstream of a turbocharger compressor, via an exhaust gas recirculation (EGR) passage, the EGR passage including an EGR valve;
• a second set of exhaust valves exclusively coupled to a second exhaust manifold coupled to an exhaust passage, upstream of a turbocharger turbine disposed in the exhaust passage;
• a plurality of engine cylinders, each including one of the first set of exhaust valves and one of the second set of exhaust valves;
• and
• a controller including memory with instructions stored thereon for:
• determining a dilution rate of gases flowing from the first set of exhaust valves to the turbocharger compressor via the EGR passage based on a first temperature of gases in the EGR passage, a second temperature of gases in the intake passage, upstream of where the EGR passage couples to the intake passage, and a third temperature of gases in the intake passage, downstream of the turbocharger compressor;
• and
• adjusting spark timing and fuel injection to the plurality of engine cylinders based on the determined dilution rate.