Engine cold-start control

An engine system coupled to a vehicle, comprising:

• an engine with an intake manifold and one or more engine cylinders;
• a direct injector for direct injecting fuel into an engine cylinder;
• a throttle valve coupled in the intake manifold, an opening of the valve adjusted by an electromechanical actuator;
• a pressure sensor for estimating a pressure of the intake manifold;
• and
• a controller configured with computer-readable instructions stored on non-transitory memory for:
• during a first engine cold-start, delivering fuel on a first combustion event of each of the one or more engine cylinders at a higher manifold pressure, and then increasing manifold pressure above the higher manifold pressure after the first combustion event;
• and
• during a second engine cold-start, lowering manifold pressure to a lower manifold pressure lower than the higher manifold pressure, delivering fuel on a first combustion event of each of the one or more engine cylinders at the lower manifold pressure, the lower manifold pressure being lowered based on an estimate of fuel temperature at an end of the injection, and then increasing manifold pressure to the higher manifold pressure after the first combustion event for a second combustion event in each of the one or more engine cylinders, the second combustion event immediately following the first combustion event of each of the one or more engine cylinders, fuel injected as a single compression stroke injection on the first combustion event of each of the one or more engine cylinders, and transitioning fuel injection to a split injection on the second combustion event, the split injection including a first portion of fuel delivered as an intake stroke injection and a second, remaining portion of the fuel delivered as a compression stroke injection.

A method for an engine comprising:

• during an engine cold-start,
• determining a fuel injection including an amount of fuel and a timing of injection based on engine operating conditions;
• lowering manifold pressure for a first combustion event of each engine cylinder at the cold-start based on an estimate of fuel temperature at an end of the injection, raising the manifold pressure for a second combustion event in each engine cylinder, the second combustion event immediately following the first combustion event of each engine cylinder;
• injecting fuel as a single compression stroke injection on the first combustion event of each engine cylinder;
• and
• transitioning fuel injection to a split injection on the second combustion event, the split injection including a first portion of fuel delivered as an intake stroke injection and a second, remaining portion of the fuel delivered as a compression stroke injection, a ratio of the first portion relative to the second portion adjusted based on temperature.