A method for operating a combustion engine is provided. A fuel injector is operated to perform a fuel injection, a sequence of pressure signals of the fuel rail pressure during the fuel injection is sampled and filtered and a total pressure difference between a first sample after a top dead center of the fuel pump and before the fuel injection has started and a chosen second sample after the injection and before a next pumping stroke is determined. A linear pressure slope at the second sample and a leakage pressure difference between the first sample and the second sample based on the linear pressure slope is calculated, leading to calculating an injection pressure difference as the difference between total pressure difference and the leakage pressure difference. With this, a value of a fuel quantity injected as a function of the injection pressure difference can be determined, while leakages are compensated.

An assembly at least comprising a fuel injector for dual fuel operation of an internal combustion engine. The assembly includes a nozzle holder defining a fuel circuit and provided with a nose adapted in use to be in connection with a combustion space of an internal combustion engine, and first and second nozzles in communication with the fuel circuit in the nozzle holder for directly injecting liquid fuel into the combustion space of the internal combustion engine for ignition of a combustible mixture present in the combustion space. The first and second nozzles adjacent to the nose of the nozzle holder are interconnected by a cooling channel. At each actuation of a fuel pump upstream of the first and second nozzles, substantially a full volume of fuel pumped during actuation of the fuel pump is allowed to flow through the cooling channel and via the first and second nozzles.

Disclosed is a method for limiting fuel leakage from at least one injector in an engine of a motor vehicle, the engine being stopped and the motor vehicle ignition circuit being switched off, the injector being supplied with fuel via a fuel rail which is pressurized during operation, the pressurization persisting for a certain period when the engine has been stopped and the ignition circuit switched off, leading to leakage of fuel through the injector. The injection rail is subjected to forced cooling following the stoppage of the engine with the motor vehicle ignition circuit switched off, which is sufficient to reduce the pressure, the forced cooling continuing until the pressure in the rail is close to atmospheric pressure.

An estimation device applicable to a combustion system having an internal combustion engine includes a mixing acquisition unit, a combustion amount estimation unit, a region estimation unit, and a timing estimation unit. The mixing acquisition unit acquires a mixing ratio of various components contained in fuel used for combustion in the internal combustion engine. The combustion amount estimation unit estimates a combustion amount of fuel caused by a post combustion generated by injecting fuel into a combustion chamber of the internal combustion engine by post injection, based on the mixing ratio acquired by the mixing acquisition unit. The region estimation unit estimates a combustion region of the post combustion in the combustion chamber based on the mixing ratio. The timing estimation unit estimates an ignition timing at which ignition occurs in the combustion chamber by the post injection based on the mixing ratio.

Methods and systems are provided for adjusting operation of fuel injectors of an internal combustion engine to reduce injector ticking noise during direct injection fuel rail pressure release. The method includes first reducing a significant part of the direct injection fuel rail pressure via a mechanical high pressure pump relief valve and only if further pressure relief is required then intermittently activating the direct injector to inject in small amount of fuel. Due to the reduced frequency of activation and small pulse-widths, the impact force transmitted from injectors to cylinder head is small thereby reducing the objectionable ticking noise.

A method for operating an internal combustion engine having a high-pressure fuel injection system stops and starts the engine independently of an intervention by the motor vehicle operator and then restarted. A high-pressure fuel pump is used to pump fuel to a high-pressure reservoir to which at least one high-pressure fuel injector is connected in order to inject fuel into the at least one cylinder of the internal combustion engine. Fuel pressure can be adjusted on the high-pressure side using an electrically actuated pressure reduction valve (PDV).

Methods and systems are provided for adjusting operation of fuel injectors of an internal combustion engine to reduce injector ticking noise during direct injection fuel rail pressure release. The method includes first reducing a significant part of the direct injection fuel rail pressure via a mechanical high pressure pump relief valve and only if further pressure relief is required then intermittently activating the direct injector to inject in small amount of fuel. Due to the reduced frequency of activation and small pulse-widths, the impact force transmitted from injectors to cylinder head is small thereby reducing the objectionable ticking noise.

A method for operating a fuel injection system with pressure reduction, and a fuel injection system that includes a fuel injection valve with a servo valve are provided. The method for operating a fuel injection system includes performing a desired pressure reduction in the pressure accumulator using at least one fuel injection valve of the fuel injection system. This is achieved by opening a servo valve in the fuel injection valve, which is opened, during a pressure reduction phase, just wide enough that the actual closing element remains closed and as a result no fuel injection process takes place.

A method for fuel regulation during a non-motoring operating mode of an internal combustion engine is provided. A fuel regulator employs a first fuel to regulate pressure of a second fuel. The first fuel is communicated to the fuel regulator through a first fuel circuit. The method comprises actuating a fuel injector that introduces the first fuel and the second fuel into a combustion chamber of the internal combustion engine during the non-motoring operating mode. The fuel injector is actuated with an injection command signal having a pulse width below a predetermined maximum value whereby no fuel is injected into the combustion chamber and the first fuel drains from the first fuel circuit through the fuel injector to a supply tank.

A method and apparatus are disclosed for determining the fuel quantity that is actually injected by a fuel injector in an internal combustion engine. A fuel injector is operated to perform a fuel injection. The first discharge stroke of the fuel pump is deactivated following a start of the fuel injection for preventing the discharge stroke from delivering fuel into the fuel rail. A value of a pressure drop caused into the fuel rail by the fuel injection is calculated. A value of a fuel quantity injected by the fuel injection is calculated on the basis of the calculated value of the pressure drop.