A method, system, and engine are configured to determine a parameter based on rotational speeds of a crankshaft, over at least three cylinder combustion cycles. The method, system, and engine determine two or more estimated crankshaft rotational speeds at two or more positions in a leading cylinder combustion cycle, two or more estimated crankshaft rotational speeds at two or more positions in a middle cylinder combustion cycle, and two or more estimated crankshaft rotational speeds at two or more positions in a following cylinder combustion cycle. The method, system, and engine are configured to determine a calculated metric based on each of the determined leading estimated crankshaft rotational speeds, the determined middle estimated crankshaft rotational speeds, and the determined following estimated crankshaft rotational speeds. An engine parameter, such as misfire, is then determined based on the calculated metric.

A method for ascertaining whether a combustion process is being carried out in a cylinder of an internal combustion engine, it being decided whether or not the combustion process is present as a function of a relative angle between a characteristic signature of a variable characterizing a time curve of a state variable of the internal combustion engine and a specifiable crankshaft angle.

An electronic central unit is configured to control a voltage application device to execute applied voltage sweep and obtain an output current that flows between a first electrode and a second electrode of an electrochemical cell. The electronic control unit is configured to detect either one of presence or absence of sulfur oxides in a specified concentration or higher in exhaust gas and a concentration of sulfur oxides in the exhaust gas based on the output current. The electronic control unit is configured to execute one of a specified determination and a specified detection based on a specified parameter. Accordingly, it is possible to accurately determine the presence or the absence of sulfur oxides in the specified concentration or higher that are contained in exhaust gas or detect the concentration of sulfur oxides in the exhaust gas.

A method for monitoring a cylinder pressure sensor, in which method the sensor value is checked for admissibility and inadmissibility in a predefinable crankshaft angle range, when admissibility is detected the cylinder pressure sensor is used further and when inadmissibility is detected the cylinder pressure sensor is deactivated. A first sensor value of the cylinder pressure sensor is set as a start value, and a second sensor value is set as a stop value, a plateau range is determined from the number of sampling steps between the start value and the stop value, and the plateau range is set as decisive for the admissibility or inadmissibility of the sensor values.

Methods and systems are disclosed for operating an engine that includes a knock control system that may determine contributions of individual transient and steady-state noise sources to an engine background noise level. The contributions of the transient and steady-state individual noise sources may be the basis for establishing the presence or absence of knock in one or more engine cylinders.

A method and system for operating a two-stroke engine includes a fuel system comprising a fuel pressure sensor, fuel temperature sensor and a fuel injector and a controller in communication with the fuel pressure sensor and fuel temperature sensor. The controller controls the fuel injector with a fuel pulsewidth determined by determining a beginning time of a window for measuring fuel pressure, determining an ending time of the window, measuring fuel pressure between the beginning time and the ending time, determining a fuel pulsewidth based on the fuel pressure and fuel temperature and injecting fuel into the two-stroke engine in response to a desired fuel mass.

A method for operating an internal combustion engine is provided in which fuel is withdrawn from a high-pressure accumulator and injected into a combustion chamber of at least one cylinder of the internal combustion engine, the method including the steps of detecting under conditions of angular synchronism a pressure of the fuel in the high-pressure accumulator during a first injection into the at least one cylinder and during a later, second injection into the at least one cylinder; ascertaining a gradient of the detected pressure; ascertaining a frequency-transformed spectrum of the detected pressure and a frequency-transformed spectrum of the ascertained gradient; correcting the frequency-transformed spectrum of the detected pressure by the frequency-transformed spectrum of the ascertained gradient; and ascertaining a cylinder-individual injection quantity of fuel, which was injected into the at least one cylinder, from the corrected frequency-transformed spectrum of the detected pressure.

Methods and systems are disclosed for operating an engine that includes a knock control system that may determine contributions of individual noise sources to an engine background noise level. The contributions of the individual noise sources may be determined via adjusting timing of a knock window or timing of the individual noise sources.

A method for predictive maintenance of components of an internal combustion engine by a structure-borne sound sensor includes: recording vibrations of the components of the internal combustion engine by at least one structure-borne sound sensor; and during operation of the internal combustion engine, continuously checking a release for diagnosing a wear condition of the components of the internal combustion engine. The one or more structure-borne sound sensors, which are arranged at one or more positions on the internal combustion engine, record measurement signals and forward them to evaluation electronics. The measurement signals are time-synchronized to a characteristic state of the internal combustion engine or the measurement signal recording is time-triggered. The time-synchronized or triggered measurement signals are decoded into measurement data. The decoded measurement data is subjected to a signal transformation. One or more spectrograms are generated from the signal transformation.

Methods and systems are disclosed for operating an engine that includes a knock control system that may determine contributions of individual noise sources to an engine background noise level. The contributions of the individual noise sources may be the basis for establishing the presence or absence of knock in one or more engine cylinders.