Systems and methods for starting and operating a direct injection engine are described. In one example, the air and fuel are injected into a pre-chamber of a cylinder of an engine while the engine is not rotating. The air and fuel are combusted in the pre-chamber to improve ignition of an air and fuel mixture in the cylinder.

Methods and systems are provided for performing expansion combustion in an engine of a start-stop vehicle. In one example, a method may include, responsive to receiving an auto-start request to restart an engine from an auto-stop, determining a fuel mass to inject into a cylinder for an expansion combustion event based on a duration of the auto-stop, and actuating a spark plug of the cylinder after injecting the determined fuel mass to perform the expansion combustion event. In this way, an air-fuel ratio of the expansion combustion event may be more accurately controlled, resulting in more robust expansion combustion engine restarts.

Methods and systems are provided for restarting an engine following an engine idle-stop. In one example, a method may include, prior to an engine restart following an idle-stop, adjusting a spark ignition timing based on an estimation of a fuel-air equivalence ratio (phi) and an estimation of a cylinder turbulence. Optimal spark ignition timing based on estimated phi and cylinder turbulence during engine restart may result in stabilized combustion and a torque output sufficient to at least partially relieve demand on the starting device.

When a vehicle is in a traveling state having a low necessity to quickly increase required traveling torque, high-rotational-speed engine starting unit that reduces an emission amount of particulate matter emitted during engine starting starts the engine. Since quick torque response is not required when the vehicle is in the traveling state having the low necessity to quickly increase the required traveling torque, the high-rotational-speed engine starting unit starts the engine, so that increase of the emission amount of particulate matter emitted during engine starting can be curbed.

Systems and methods for stopping and starting a direct injection engine are described. In one example, the air is injected into one or more pre-chambers of engine cylinders to adjust engine pumping torque during an engine stop so that the engine may stop at a crankshaft position that facilitates direct engine starting.

A powertrain system includes a port injection internal combustion engine. A first start process is a process in which fuel is enclosed in a compression stroke cylinder when the engine is stopped, and based on a stored crank stop position, ignition is performed in a first cycle of the compression stroke cylinder upon engine start. A second start process is a process in which, based on the stored crank stop position, fuel injection is performed for an intake stroke cylinder while the engine is stopped, and based on the stored crank stop position, ignition is performed in the first cycle of the intake stroke cylinder upon engine start. When a catalyst temperature at the time engine start is requested is equal to or higher than a first threshold, a control device starts the internal combustion engine by at least one of the first start process and the second start process.

A fuel supply apparatus is operated so as to increase an upon-stopping fuel pressure in accordance with an increase in an upon-stopping vehicle speed, the upon-stopping fuel pressure being a fuel pressure in a state in which an internal combustion engine is intermittently stopped, the upon-stopping vehicle speed being a vehicle speed upon intermittently stopping the internal combustion engine.

A method for starting an internal combustion engine and a motor vehicle are provided. The internal combustion engine includes a plurality of cylinders. To start the internal combustion engine while deactivated, a predefined amount of working gas is introduced into the cylinder that fires first. A crankshaft of the internal combustion engine is driven by an electric motor and by the movement of a piston coupled to the crankshaft and associated with the cylinder that fires first to introduce the predefined amount of working gas. Subsequently, the internal combustion engine is started by the ignition of a mixture including the predefined amount of working gas and a predefined amount of fuel inside the cylinder that fires first.

A method of implementing control logic of a compression-ignition engine is provided. A controller outputs a signal to a injector and a variable valve operating mechanism so that a gas-fuel ratio (G/F) becomes leaner than a stoichiometric air fuel ratio, and an air-fuel ratio (A/F) becomes equal to or richer than the stoichiometric air fuel ratio, and to an ignition plug so that unburnt mixture gas combusts by self-ignition after the ignition plug ignites mixture gas inside a combustion chamber. The method includes steps of determining a geometric compression ratio and determining the control logic defining an intake valve close timing IVC. IVC (deg.aBDC) is determined so that the following expression is satisfied: if the geometric compression ratio is 10<17,
0.4234.sup.222.926+207.84+CIVC0.4234.sup.2+22.926167.84+C
where C is a correction term according to an engine speed NE (rpm),
C=3.310.sup.10NE.sup.31.010.sup.6NE.sup.2+7.010.sup.4NE.

In response to a restarting request generated during a stopping period, in which fuel injection is stopped to automatically stop engine operation, either starter starting or combustion starting is selected. In the starter starting, the engine is restarted using a starter motor. In the combustion starting, the engine is restarted through fuel injection and ignition without using the starter motor. If the rotational resistance acting on the crankshaft is determined to be of such a magnitude that the combustion starting is impossible, the starter starting is carried out in response to the restarting request generated during the stopping period.