An engine system is provided, including a controller which estimates an intake-valve-closing temperature inside a cylinder. When an engine operates at a given speed and a demanded engine load is a first load or a second load (>the first load), the controller controls so that a mixture gas inside the cylinder combusts by compression ignition, and controls so that, at the first load, the entire mixture gas combusts by compression ignition when the intake-valve-closing temperature is above a first temperature, and at least part of the mixture gas combusts by flame propagation when the intake-valve-closing temperature is below the first temperature, whereas at the second load, the entire mixture gas combusts by compression ignition when the intake-valve-closing temperature is above a second temperature (<the first temperature), and at least part of the mixture gas combusts by flame propagation when the intake-valve-closing temperature is below the second temperature.

A method for calculating the mass of an overlap gaseous flow (M.sub.OVL), wherein the exhaust pressure is higher than the intake pressure, or in the case of scavenging (SCAV), wherein the intake pressure is higher than the exhaust pressure. The overlap gaseous flow (M.sub.OVL) is the flow which flows, in overlap conditions, through the intake valve and the exhaust valve of a cylinder of an internal combustion engine. At least one intake valve is driven so as to vary the lift (H) of the intake valve in controlled manner. The overlap condition is a condition in which the intake valve and the exhaust valve are both at least partially open. The method comprises calculating the mass of the gaseous flow (M.sub.OVL) which flows through the intake valve and the exhaust valve on the basis of the relation:
M.sub.OVL=PERM*β(P/P.sub.0,n)*P.sub.0/P.sub.0_REF*(T.sub.0_REF/T.sub.0).sup.1/2/n.

An engine system is provided, including a controller which estimates a mass ratio (G/F) of intake air inside a cylinder (containing fresh air and burnt gas) to fuel, and controls devices of an engine at a given engine speed so that, while a demanded engine load is a first load, at least part of a mixture gas inside the cylinder combusts by flame-propagation when the estimated G/F is below a first G/F, and the entire mixture gas combusts by compression ignition when the estimated G/F is above the first G/F, whereas while the demanded load is a second load (>the first load), at least part of the mixture gas combusts by flame-propagation when the estimated G/F is below a second G/F (<the first G/F), and the entire mixture gas combusts by compression ignition when the estimated G/F is above the second G/F.

Methods and systems for supplying post injection fuel to a two stroke diesel engine are described. In one example, post injection fuel timing is adjusted responsive to an amount of internal residual combustion products in a cylinder so that less post injected fuel may be trapped in the cylinder for a subsequent cycle of the cylinder. The start of post injection fuel timing and the amount of post injection fuel may be adjusted responsive to internal residual in the cylinder.

A system includes a fuel control module and a valve control module. The fuel control module controls a fuel injector to stop fuel delivery to each cylinder of an engine in a vehicle when the vehicle is decelerating. The valve control module controls a valve actuator to actuate intake and exhaust valves of each cylinder of the engine between open and closed positions when fuel delivery to each cylinder of the engine is stopped. The valve control module controls the valve actuator to adjust an amount of airflow through each cylinder of the engine to a minimum amount when fuel delivery to each cylinder of the engine is initially stopped. The valve control module controls the valve actuator to adjust the amount of airflow through each cylinder of the engine to an amount greater than the minimum amount before fuel delivery to each cylinder of the engine is restarted.

A system and method is provided for controlling an electric machine rotatably coupled to a rotatable shaft of an electronically-controlled one of a turbocharger and an exhaust-driven turbo supercharger fluidly coupled to an exhaust duct of an internal combustion engine. An operating temperature of a component of the engine is determined or estimated an operating temperature of a component of the engine or coupled to the engine, which is compared to a threshold temperature. The electric machine is controlled to operate as a motor in response to the determined or estimated temperature of the component being below a threshold temperature.

A method for controlling the air-fuel ratio of a vehicle includes: calculating the air amount charged in a cylinder of an engine by using a fresh air amount, a residual air amount remaining inside the cylinder of the engine, and a backflow gas amount flowing back into the cylinder upon the valve overlap of an intake vale and an exhaust valve of the engine, correcting it with the purge gas flow rate supplied to an intake manifold of the engine when the active purge system is operated, calculating the final fuel amount by correcting the fuel amount injected by a fuel injection device with the amount of the fuel component contained in the purge gas when the active purge system is operated, and controlling the air-fuel ratio based on the final air amount and the final fuel amount.

An apparatus includes an engine module, an in-cylinder content module, and an engine out NOx module. The engine module is structured to interpret engine in-cylinder data regarding an operating condition within a cylinder of an engine, wherein the engine in-cylinder data includes an engine torque, an engine speed, a rail pressure, and a start-of-injection. The in-cylinder content module is structured to interpret at least one additional in-cylinder data point regarding the operating condition within the cylinder of the engine. The engine out NOx module is structured to determine an engine out NOx amount responsive to the engine in-cylinder data and the at least one additional in-cylinder data point.

An Exhaust Gas Recirculation (EGR) effective flow diagnosis method includes: measuring an EGR gas temperature by an EGR gas temperature sensor under an EGR gas temperature rise condition of an EGR system on an intake line; determining the degree of the EGR gas temperature rise; and determining whether an EGR effective flow is excessive or insufficient according to the degree of the EGR gas temperature rise.

A compression ignition gasoline engine includes a fuel injection valve for injecting fuel containing gasoline as a main component into a cylinder; an EGR device operative to perform high-temperature EGR of introducing burnt gas generated in the cylinder into the cylinder at a high temperature; an octane number determination unit for determining whether fuel injected from the fuel injection valve has a prescribed octane number; and a combustion control unit for controlling the fuel injection valve and the EGR device in such a way that HCCI combustion occurs within the cylinder. The combustion control unit controls the EGR device, in at least a partial load operating range in which HCCI combustion is performed, in such a way that the EGR rate increases, as compared with a case where fuel is determined to have a prescribed octane number, when fuel is determined not to have a prescribed octane number.