Various systems and methods are described for diagnosing injector variability in a dual fuel, multi-injector system. In one example, a single injector in one cylinder is enabled while remaining cylinders are fueled with a first fuel and subsequently, a second fuel is injected via the enabled injector into the one cylinder in a predetermined sequence and fuel rail pressure drops are measured. Further, measured pressure drop after each injection event is corrected for an increase in injector closing delay.

A hydrogen-diesel direct injection dual-fuel system for an internal combustion engine enables retrofitting to existing diesel engines. The system comprises: a cylinder head of the engine having a first and a second injector hole; a diesel pilot injector positioned in the first injector hole; and a hydrogen injector positioned in the second injector hole; wherein the hydrogen injector comprises: a gasoline direct injector having an external shank and a distal output end; and a nozzle cap covering the distal output end, wherein the nozzle cap is welded to the external shank.

A bi-fuel control system can include an electronic control module and a control unit that are in communication with each other. The system can include a first set of fuel injectors that are configured to deliver a primary fuel to an engine and can include a second set of fuel injectors that are configured to deliver a secondary fuel to the engine. The bi-fuel control system can operate in either a primary operational state in which the first set of injectors is used or a secondary operational state in which the second set of injectors is used. In either operational state, the electronic control module can control the respective set of injectors independently from the control unit.

A method for controlling an internal-combustion engine includes detecting knocking in the internal-combustion engine. An EGR gas quantity of EGR gas is increased in a case where the knocking is detected. A part of exhaust gas is circulated into an intake passage as the EGR gas. A fuel octane number of fuel supplied to a cylinder is increased in the case. The fuel octane number is decreased after the fuel octane number has been increased. The EGR gas quantity is maintained so as to prevent the knocking after the EGR gas quantity has been increased.

A two-stroke uniflow engine is provided with: a cylinder; a piston; an exhaust valve that is opened and closed in order to discharge exhaust gas that is generated inside the cylinder; a scavenging port that takes active gas into the interior of the cylinder in accordance with a sliding movement of the piston; a fuel injection port that is provided in the internal circumferential surface of the cylinder; a fuel injection valve that injects fuel gas into the fuel injection port; and a fuel injection control unit that executes control of the injection of the fuel gas in the fuel injection valve, wherein the fuel injection control unit decides at least one of an injection pressure and an injection time of the fuel injection valve based on a change in pressure inside the cylinder that is caused by a reciprocating movement of the piston.

A method for optimal fueling of an engine is disclosed. The method includes determining a quantity of exhaust residuals in each cylinder among a plurality of cylinders in the engine. Further, the method includes determining at least one of an intake and exhaust manifolds temperature, at least one of an intake and exhaust manifolds pressure, and a quantity of a first fuel being injected to each cylinder, and calculating a characteristic temperature of each cylinder based on the quantity of exhaust residuals, at least one of the intake and exhaust manifolds temperature and pressure, and the quantity of the first fuel. The method further includes determining a substitution rate of the first fuel for each cylinder based on the characteristic temperature, and controlling at least one of the quantity of the first fuel, and a quantity of a second fuel being injected to each cylinder based on the substitution rate.

Methods of operation of liquid and gaseous multi-fuel compression ignition engines that may be operated on a gaseous fuel or a liquid fuel, or a combination of both a gaseous fuel and a liquid fuel at the same time and in some embodiments, in the same combustion event. Various embodiments are disclosed.

A control device includes first and second level ratio calculators and an adjuster. The first level ratio calculator calculates a first level ratio of an amount of a first fuel stored in a first tank to a full tank capacity of the first tank. The second level ratio calculator calculates a second level ratio of an amount of a second fuel stored in a second tank to a full tank capacity of the second tank. An octane number of the second fuel is higher than an octane number of the first fuel. The adjuster adjusts a first fuel ratio of the first fuel in a supplied fuel which is supplied to an internal combustion engine and a second fuel ratio of the second fuel in the supplied fuel such that a deviation ratio of the first level ratio and the second level ratio is within a predetermined range.

A fuel system comprises a first fuel rail. A first fuel delivery system, including a first plurality of fuel injectors, is connected to the first fuel rail. The first plurality of fuel injectors injects an amount of fuel into a first portion of an engine. A second fuel rail has a second fuel delivery system, including a second plurality of fuel injectors. The second plurality of fuel injectors inject an amount of fuel into a second portion of the engine, distinct from the first portion. A controller, operatively connected to the first fuel delivery system and the second fuel delivery system selectively enables and disables operation of the first fuel delivery system and the second fuel delivery system based on one of a detected temperature and a detected pressure of fuel passing to corresponding ones of the first plurality of fuel injectors and the second plurality of fuel injectors.

In a control system for an internal combustion engine that can use a plurality of kinds of fuel including compressed natural gas, the invention prohibits a changeover from CNG to another fuel from being made in a period from a time when CNG is used for the first time after the start of the internal combustion engine to a time when it is determined that properties of CNG do not need to be learned, or a period from the time when CNG is used for the first time after the start of the internal combustion engine to a time when a processing of learning the properties of CNG ends.