A system and method monitor operation of a compressor, determine whether the operation of the compressor is outside of a designated range of values, and, responsive to determining that the operation of the compressor is outside of the designated range of values, one or more of (a) prevent communication of a signal to a system controller that controls operation of the compressor, (b) direct a gas from a reservoir to a pressure sensor used by the system controller to determine a gas pressure generated by the compressor, and/or (c) communicate the signal to the system controller that controls operation of the compressor.

A system and method monitor operation of a compressor, determine whether the operation of the compressor is outside of a designated range of values, and, responsive to determining that the operation of the compressor is outside of the designated range of values, one or more of (a) prevent communication of a signal to a system controller that controls operation of the compressor, (b) direct a gas from a reservoir to a pressure sensor used by the system controller to determine a gas pressure generated by the compressor, and/or (c) communicate the signal to the system controller that controls operation of the compressor.

A method and system are provided with which it is possible to detect non-firing and untimely firing events in internal combustion and, if necessary, the temperature of the gas in the exhaust gas pipe. This is performed in general by measuring the speed of sound and determining the phase angle between the sender and receiver either arranged on different sides of the exhaust gas pipe or on the same side of the exhaust gas pipe. The receiver, depending on the measurement principle, can include one, two, or in special applications three receivers. Additionally, if necessary, it is possible to suppress the structure-borne sound influence on a speed of sound measurement with low cost and high stability.

A method and system are provided with which it is possible to detect non-firing and untimely firing events in internal combustion and, if necessary, the temperature of the gas in the exhaust gas pipe. This is performed in general by measuring the speed of sound and determining the phase angle between the sender and receiver either arranged on different sides of the exhaust gas pipe or on the same side of the exhaust gas pipe. The receiver, depending on the measurement principle, can include one, two, or in special applications three receivers. Additionally, if necessary, it is possible to suppress the structure-borne sound influence on a speed of sound measurement with low cost and high stability.

A method of determining the acceleration of a crankshaft of an internal combustion engine including one or more cylinders, with respect to each combustion event, n, among a plurality of combustion events, includes a) providing a signal indicative of crankshaft speed, with the signal including a series of minima and maxima speeds with respect to each successive combustion event and b) determining the acceleration of the crankshaft of the internal combustion engine with respect to each combustion event, n, among the plurality of combustion events, based on an initial speed value of a minima, Min (n) just before the combustion event, n, and a subsequent speed value of a maximum, Max (n) immediately subsequent to the combustion event, n, in addition to a speed of a minima for a subsequent combustion event, Min (n+1).

A method of determining the acceleration of a crankshaft of an internal combustion engine including one or more cylinders, with respect to each combustion event, n, among a plurality of combustion events, includes a) providing a signal indicative of crankshaft speed, with the signal including a series of minima and maxima speeds with respect to each successive combustion event and b) determining the acceleration of the crankshaft of the internal combustion engine with respect to each combustion event, n, among the plurality of combustion events, based on an initial speed value of a minima, Min (n) just before the combustion event, n, and a subsequent speed value of a maximum, Max (n) immediately subsequent to the combustion event, n, in addition to a speed of a minima for a subsequent combustion event, Min (n+1).

A CPU stops combustion control of Cylinder #1 in order to perform a regeneration process of a GPF and performs a regeneration process of causing an air-fuel ratio of an air-fuel mixture in Cylinders #2 to #4 to be richer. When it is determined that a misfire has occurred because a misfire rate when the regeneration process is not being performed is equal to or greater than a predetermined value, the CPU determines that an internal combustion engine has returned to a normal state based on the premise that the misfire rate when the regeneration process is not being performed decreases.

A CPU stops combustion control of Cylinder #1 in order to perform a regeneration process of a GPF and performs a regeneration process of causing an air-fuel ratio of an air-fuel mixture in Cylinders #2 to #4 to be richer. When it is determined that a misfire has occurred because a misfire rate when the regeneration process is not being performed is equal to or greater than a predetermined value, the CPU determines that an internal combustion engine has returned to a normal state based on the premise that the misfire rate when the regeneration process is not being performed decreases.

A straddled vehicle engine unit including an internal combustion engine and a misfire detection device. The internal combustion engine has a crankshaft, and a crank angle signal output unit that periodically outputs a crank angle signal in accordance with rotation of the crankshaft. The internal combustion engine is configured to repeat at least two kinds of strokes on a cycle of every 720-degree rotation of the crankshaft. The misfire detection device includes a crankshaft rotation speed fluctuation physical quantity acquisition unit configured to acquire a physical quantity related to an amount of fluctuation in a rotation speed of the crankshaft in one kind of stroke, out of the at least two kinds of strokes, based on the crank angle signal from the crank angle signal output unit, and a misfire determination unit configured to perform a misfire determination in response to each acquisition of the crankshaft rotation speed fluctuation physical quantity.

An internal combustion engine includes an internal combustion engine main body including a plurality of cylinders, a knock sensor provided on each of the plurality of cylinders, a control board including an amplification circuit, and a plurality of cables differing in length and each connecting the knock sensor and the control board. The amplification circuit includes, for each of the plurality of cables, a first charge amplifier connected to a first output terminal of the knock sensor via one of the plurality of cables, a second charge amplifier connected to a second output terminal of the knock sensor via one of the plurality of cables, and a differential amplifier configured to take an output of the first charge amplifier and an output of the second charge amplifier as input.