Methods and systems are provided for calculating a fuel aging of fuel in a fuel tank. In one example, a method may include alerting a vehicle operator and/or adjusting engine operating parameters in response to a fuel aging being greater than a threshold aging.

An engine diagnostic system is provided for diagnosing a deterioration degree of an engine mounted on a vehicle. The engine diagnostic system learns, as a knock learning value, a maximum advancement amount of an ignition timing that reduces knocking. A database stores time-series data of the knock learning value of the engine for each individual engine. The knock learning value is acquired from each of a plurality of vehicles of the same model. An evaluation process computes an evaluation value indicating the deterioration degree of a designated engine using the time-series data of the knock learning value of each engine stored in the database.

A control apparatus for a vehicle includes: a characteristic storage portion configured to store therein torque-characteristic information representing an output torque characteristic as a characteristic of an output torque of an engine of the vehicle, which has appeared in a certain control operation, such that the stored torque-characteristic information is divided into a plurality of groups corresponding to respective refueling points that provide the fuel; and a factor determination portion configured, when the output torque characteristic represented by the torque-characteristic information belonging to one of the plurality of groups and the output torque characteristic represented by the torque-characteristic information belonging to another one of the plurality of groups are different from each other and a characteristic difference therebetween is not smaller than a threshold value, to determine that the characteristic difference is caused by a difference in a property of the fuel.

A method and a device are provided for controlling an internal combustion engine, a knock sensor being provided for acquiring combustion signals of the internal combustion engine. Devices are also provided that, during running operation of the internal combustion engine, select operating ranges of the internal combustion engine that are suitable for a determination of fuel quality, and carry out a determination of the fuel quality in these ranges on the basis of signals of the knock sensor.

Various methods and systems are provided for correcting relative error between a gaseous fuel torque estimate and a liquid fuel torque estimate in a multi-fuel engine. A system (e.g., a system for an engine) may include a controller with computer readable instructions stored on non-transitory memory that when executed during operation of the engine cause the controller to: operate the engine at a first substitution ratio of gaseous fuel and liquid fuel; correct for relative error between a gaseous fuel to torque conversion factor and a liquid fuel to torque conversion factor; and upon correcting for the relative error, operate the engine at a second substitution ratio, higher than the first substitution ratio.

Various embodiments of the present disclosure relate to methods and systems for measuring an injected fuel quantity during multipulse injection events in a common rail of a fuel system including a fuel pump to supply fuel to the common rail. The method, using a control unit, determines if each of the multipulse injection events in a normal operating condition includes a pilot pulse; in response to determining that the pilot pulse is included, obtaining an enforced separation value between the pilot pulse and the main pulse to emulate a single-pulse injection; while the fuel pump is temporarily shut off, performing a temporary enforced separation on a fraction of the multipulse injection events; measuring a pressure change in the common rail during the temporary enforced separation; and resuming the normal operating condition of the multipulse injection events after the pressure change is measured.

An estimation device is applicable to a combustion system including an internal combustion engine. The estimation device includes a mixing acquisition unit, a combustion amount estimation unit, and a region estimation unit. The mixing acquisition unit acquires the mixing ratio of various components contained in the fuel used for combustion in the internal combustion engine. The combustion amount estimation unit estimates a main combustion amount of the fuel caused by a main combustion produced by injecting the fuel into a combustion chamber of the internal combustion engine with a main injection, based on the mixing ratio acquired by the mixing acquisition unit. The region estimation unit estimates a combustion region of the main combustion in the combustion chamber based on the mixing ratio acquired by the mixing acquisition unit.

A method for operating an internal combustion engine with detection of the fuel used for injection is described. In the method, the elasticity modulus of the fuel to be injected is determined at a first and a second injection pressure. A difference value is calculated from the difference between the two elasticity modulus values related to the pressure difference and is compared with a differentiating value. The fuel being used is detected depending on whether the difference value is above or below the differentiation value. In particular, the method is used for differentiating diesel fuel EN590 and biodiesel.

Methods and systems are provided for characterizing aged fuel, which loses volatility over time. In one example, a method may include estimating a fuel vapor pressure during an engine cold start using a pre-determined fuel distillation curve and adjusting one or more combustion parameters based on the estimated fuel vapor pressure. Because the fuel vapor pressure directly relates to the fuel volatility, adjusting the one or more combustion parameters based on the estimated fuel vapor pressure may reduce aged fuel-related engine performance degradation, such as hesitation and emissions during cold start.

A fuel passage leads a fuel from a pressure-accumulation vessel to a nozzle hole of a fuel injection valve. A fuel pressure sensor detects a fuel pressure in a fuel passage. An estimation device is applicable to a combustion system, which includes these components, and includes a mixing acquisition unit and an injection amount estimation unit. The mixing acquisition unit acquires the mixing ratio of various components contained in the fuel used for combustion in the internal combustion engine. The injection amount estimation unit estimates an injection amount of the fuel from the nozzle hole according to a change mode of the fuel pressure, which is detected with the fuel pressure sensor and associated with injection of the fuel from a nozzle hole, and the mixing ratio acquired with the mixing acquisition unit.