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.

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.

Systems and methods for operating an engine that is started via expansion stroke combustion are described. In one example, the method increases air flow through the engine during an engine stopping process so that a larger amount of air may be trapped in a cylinder that is on its expansion stroke so that greater amounts of engine torque may be provided during engine starting.

The invention relates to a method for starting operation of an internal combustion engine, wherein the method comprises the steps of: when the internal combustion engine is not operating, providing pressurized gas in the air intake duct; opening the intake valve in a first cylinder while keeping the exhaust valve of the first cylinder closed so as to allow the pressurized gas to enter the first cylinder, press onto the corresponding piston and thereby move the corresponding piston and rotate the crank shaft; supplying fuel to at least one of the cylinders where the corresponding piston has performed or is performing a compression step so as to ignite the fuel and start operation of the engine.

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 operating an engine that is started via expansion stroke combustion are described. In one example, the method increases air flow through the engine during an engine stopping process so that a larger amount of air may be trapped in a cylinder that is on its expansion stroke so that greater amounts of engine torque may be provided during engine starting.

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.

An internal combustion engine includes cylinders that are divided into a first cylinder group and a second cylinder group, a cylinder reduction mechanism that holds intake valves and exhaust valves of the first cylinder group in closed states so as to establish a reduced-cylinder state. When the engine is stopped in the reduced-cylinder state, the electronic control unit provided in the engine starts the engine by ignition, by executing fuel injection and ignition in an expansion-stroke cylinder. When the first cylinder group includes an exhaust-stroke cylinder, the engine is started by ignition through fuel injection and ignition in the expansion-stroke cylinder, after a piston is moved in a reverse direction through fuel injection and ignition in the exhaust-stroke cylinder. When the first cylinder group does not include the exhaust-stroke cylinder, the engine is started by ignition, through fuel injection and ignition in the expansion-stroke cylinder and an intake-stroke cylinder.

An electronic control unit is configured to calculate an amount of divergence of an actual MG rotational speed with respect to a reference rotational speed at the start-up of an internal combustion engine, and correct a generation timing of a compensation torque at the next start-up of the internal combustion engine based on the amount of divergence.

A start control device of a vehicular direct injection engine provided in a vehicle is configured to execute an ignition start to raise rotation of the direct injection engine at a start of the direct injection engine by fuel injection and multiple sparking performed for a predetermined cylinder in an expansion stroke out of multiple cylinders of the direct injection engine, the start control device of a vehicular direct injection engine reduces the number of times of sparking for the predetermined cylinder at the time of an ignition start of the direct injection engine as compared to an ignition start performed before the current ignition start based on ignition timing of the ignition start performed before the current ignition start.