A control system and a control method for an internal combustion engine, which are capable of accurately calculating an in-cylinder gas amount and an EGR ratio by a relatively simple method even in a case where an in-cylinder gas temperature is changed by execution of internal EGR, and properly controlling the engine using the EGR ratio thus calculated. An in-cylinder gas amount Gact actually filled in the cylinder is calculated by correcting an ideal in-cylinder gas amount Gth, which is an amount of gases filled in a cylinder in an ideal state in which it is assumed that no exhaust gases of the engine are recirculated into the cylinder, using an ideal in-cylinder gas temperature Tcylth according to an in-cylinder gas temperature Tcyl, and an EGR ratio REGRT is calculated using the in-cylinder gas amount Gact and an intake air amount Gaircyl.

A method of operating an internal combustion engine, whereby a quantity of an exhaust gas remaining in combustion chambers of the internal combustion engine is varied, whereby the quantity of remaining exhaust gas is varied by controlling or regulating an exhaust-gas backpressure (p.sub.outlet) adjacent to outlet valves of the combustion chambers of a turbo-compound system arranged in an exhaust pipe of the internal combustion engine.

When the starting timing of a negative valve overlapping (NVO) period exists at the delayed-angle side of the starting timing of a first NVO period, fuel injection into a cylinder is not started; when the starting timing of an NVO period exists between the starting timing of the first NVO period and the starting timing of the second NVO period, fuel injection into the cylinder is started at a given timing that includes the exhaust top dead center; when the starting timing of an NVO period exists between the starting timing of the second NVO period and the starting timing of the third NVO period, fuel injection into the cylinder is started at a given timing that does not include the exhaust top dead center, and that exists at both the advanced-angle and delayed-angle sides of the exhaust top dead center.

An engine controller controls a direct fuel-injection engine including a fuel injection valve for directly injecting a fuel into a cylinder and a valve overlap period adjusting mechanism for adjusting a valve overlap period between an open period of an intake valve and an open period of an exhaust valve. The engine controller is provided with an acceleration request sensor for detecting an acceleration request of a driver, and when the acceleration request occurs and a top surface temperature of a piston in the cylinder is lower than a predetermined temperature, the engine controller extends the valve overlap period between the open period of the intake valve and the open period of the exhaust valve, ranging before and after an exhaust top dead center.

Systems and methods for improving engine low load performance are provided. The method may comprise performing a negative valve overlap (NVO) mode of operation, using an early exhaust valve closing (EVC) timing that is earlier than the intake valve opening timing and creates an NVO during a gas exchange top dead center, to compress in-cylinder gas and increase overall gas temperature for improved fuel vaporization, mixing, and reforming before the fuel-air mixture is burnt. With NVO operation, a low temperature combustion (LTC) mode may be used to improve engine combustion efficiency and reduce emissions. With the NVO operation at low loads, the engine intake may be wide open or less throttled, reducing pumping loss. A method based on a rate of change in the engine speed and load for the combustion mode transition between spark ignition (SI) and LTC modes is provided.

The disclosure concerns a method and a control arrangement for controlling valve actuation of an ICE comprising an exhaust valve, an intake valve, and a turbo compressor. The method comprises and the control arrangement is configured to: limiting/limit valve actuation changes of the exhaust and intake valves based on compressor data including surge limit data for the turbo compressor and one or both of a current turbo compressor rotational speed and a current turbo compressor pressure ratio, to maintain a turbo compressor mass flow above a limit mass flow value.

It is a challenge to reduce unburned hydrocarbon emissions for gaseous fuelled engines, especially at low engine load conditions, to meet demanding emission regulation targets. A method for reducing unburned hydrocarbon emissions in a lean-burn internal combustion engine that is fuelled with a gaseous fuel comprises adjusting the timing for closing of an intake valve as a function of engine operating conditions by one of advancing timing for closing of the intake valve and closing the intake valve earlier during an intake stroke; and retarding timing for closing of the intake valve and closing the intake valve later during a compression stroke. The volumetric efficiency of the internal combustion engine is reduced and unburned hydrocarbon emissions are maintained below a predetermined level.

An engine controller controls a direct fuel-injection engine including a fuel injection valve for directly injecting a fuel into a cylinder and a valve overlap period adjusting mechanism for adjusting a valve overlap period between an open period of an intake valve and an open period of an exhaust valve. The engine controller is provided with an acceleration request sensor for detecting an acceleration request of a driver, and when the acceleration request occurs and a top surface temperature of a piston in the cylinder is lower than a predetermined temperature, the engine controller extends the valve overlap period between the open period of the intake valve and the open period of the exhaust valve, ranging before and after an exhaust top dead center.

A direct injection engine includes a fuel injection valve configured to inject fuel into a cylinder, a water injection valve configured to inject water into the cylinder, and a valve variable mechanism configured to change an operation timing of each of an intake valve and an exhaust valve. During an operation in a low load range, a negative overlap period when both of the intake valve and the exhaust valve are closed across an exhaust top dead center is formed by the valve variable mechanism, and fuel is injected from the fuel injection valve and water is injected from the water injection valve respectively during the negative overlap period. This causes a steam reforming reaction such that at least a part of injected fuel and injected water turns to hydrogen and carbon monoxide within the cylinder during the negative overlap period.

An internal combustion engine is described. Controlling the internal combustion engine includes gathering engine operating data during steady-state engine operation, including gathering a first dataset associated with a cylinder air charge during steady-state operation of the engine in the PVO state and gathering a second dataset associated with a cylinder air charge during steady-state operation of the engine in the NVO state. An optimization routine is executed to determine a first subset of parameters associated with a first relationship for a cylinder air charge model based upon the second dataset. The optimization routine is also executed to determine a second subset of parameters associated with a second relationship for the cylinder air charge model based upon the first dataset. A cylinder air charge is determined in real-time during engine operation based upon the cylinder air charge model and the first and second subsets of parameters.