A method of operating a two-stroke cycle, opposed-piston engine comprising a pumping device coupled to pump air to cylinders of the engine through a charge air cooler and an aftertreatment system of thermally-activated devices coupled to receive exhaust from the cylinders by which a thermal state of the exhaust sufficient to sustain thermal activation of one or more of the aftertreatment system devices may be maintained during a deceleration or motoring condition of operation by reducing the mass airflow to the engine.

A method of operating a two-stroke cycle, opposed-piston engine comprising a pumping device coupled to pump air to cylinders of the engine through a charge air cooler and an aftertreatment system of thermally-activated devices coupled to receive exhaust from the cylinders by which a thermal state of the exhaust sufficient to sustain thermal activation of one or more of the aftertreatment system devices may be maintained during a deceleration or motoring condition of operation by reducing the mass airflow to the engine.

Various embodiments include a method for operating an internal combustion engine wherein the compression is variably adjusted comprising: checking a sensor signal indicative of a compression of the engine; checking the plausibility of the signal by: ascertaining a series of corresponding values of the signal and values of the actuating variable; determining a mathematical relationship between the signal and the variable based on the series; determining a deviation between the relationship and a predetermined characteristic relationship; and determining the signal is plausible when the determined deviation is lower than a predetermined threshold value; and if the determined deviation is higher than the predetermined threshold value, adjusting operation of the internal combustion engine.

Various embodiments include a method for operating an internal combustion engine wherein the compression is variably adjusted comprising: checking a sensor signal indicative of a compression of the engine; checking the plausibility of the signal by: ascertaining a series of corresponding values of the signal and values of the actuating variable; determining a mathematical relationship between the signal and the variable based on the series; determining a deviation between the relationship and a predetermined characteristic relationship; and determining the signal is plausible when the determined deviation is lower than a predetermined threshold value; and if the determined deviation is higher than the predetermined threshold value, adjusting operation of the internal combustion engine.

A controller is configured to execute a dither control process of operating fuel injection valves such that at least one of cylinders is a lean combustion cylinder, in which the air-fuel ratio is leaner than the stoichiometric air-fuel ratio, and at least another one of the cylinders is a rich combustion cylinder, in which the air-fuel ratio is richer than the stoichiometric air-fuel ratio, and a limiting process of limiting the dither control process such that the difference in the air-fuel ratio between the cylinders is smaller in a change period, in which a gear ratio of the multi-speed transmission is changed, than in periods except for the change period.

A controller is configured to execute a dither control process of operating fuel injection valves such that at least one of cylinders is a lean combustion cylinder, in which the air-fuel ratio is leaner than the stoichiometric air-fuel ratio, and at least another one of the cylinders is a rich combustion cylinder, in which the air-fuel ratio is richer than the stoichiometric air-fuel ratio, and a limiting process of limiting the dither control process such that the difference in the air-fuel ratio between the cylinders is smaller in a change period, in which a gear ratio of the multi-speed transmission is changed, than in periods except for the change period.

The start control device is provided with: a determination unit 110 for determining, when an engine 10 is being started, whether or not the engine 10 is in a prescribed cold-start state; and a start control unit 120 for causing, when the determination unit 110 determines that the engine is in the cold-start state, fuel injection to the engine 10 to be suspended and the engine 10 to be cranked for a preset threshold time by transmitting a torque from a starter motor 63 to a crankshaft 16 while, and starting fuel injection to the engine 10 once the threshold time elapses after the cranking is started.

An ECU makes an opening degree of a throttle valve larger than an opening degree in an idle rotating state of an engine in a rotation drop period during which engine speed drops to zero after combustion of the engine is stopped. Further, the ECU determines that the engine speed is within a predetermined rotation speed range including at least a resonance range of the engine in the rotation drop period, and, in the case where it is determined that the engine speed is within the predetermined rotation speed range, the ECU performs rotation drop processing of temporarily increasing a drop rate of the engine speed.

An ECU makes an opening degree of a throttle valve larger than an opening degree in an idle rotating state of an engine in a rotation drop period during which engine speed drops to zero after combustion of the engine is stopped. Further, the ECU determines that the engine speed is within a predetermined rotation speed range including at least a resonance range of the engine in the rotation drop period, and, in the case where it is determined that the engine speed is within the predetermined rotation speed range, the ECU performs rotation drop processing of temporarily increasing a drop rate of the engine speed.

Provided is a piston temperature state monitoring system for an internal combustion engine and a piston temperature monitoring method for an internal combustion engine which are capable of properly managing a history of a piston temperature. When the number of times of a piston temperature suppression control is counted, if a ratio of a temperature difference which is the difference between a maximum limit temperature and a piston temperature to a margin width which is the difference between the maximum limit temperature and a control start temperature is equal to or less than a count threshold ratio set in advance or calculated, a count output system outputs a count signal.