To keep medium purification efficiency at a high level and prevent deterioration of emission performance. An aspect of the present invention includes: a downstream equivalence ratio calculation unit that calculates a catalyst downstream exhaust gas equivalence ratio by using a catalyst statistical model that receives at least a detection value of an air-fuel ratio sensor on an upstream side of a catalyst and outputs a catalyst downstream exhaust gas equivalence ratio; an oxygen output calculation unit that calculates an output value of an oxygen sensor by using an oxygen sensor statistical model that receives the catalyst downstream exhaust gas equivalence ratio and outputs an output value of the oxygen sensor on the downstream side of the catalyst; a downstream equivalence ratio correction unit that corrects the catalyst downstream exhaust gas equivalence ratio calculated by the downstream equivalence ratio calculation unit based on a calculation result of the oxygen output calculation unit and the detection value of the oxygen sensor; and an air-fuel ratio control unit that controls an air-fuel ratio of an air-fuel mixture of an internal combustion engine based on the corrected catalyst downstream exhaust gas equivalence ratio and air-fuel ratio target value.

An assembly for determining lambda values of an exhaust gas of an internal combustion engine is provided. The internal combustion engine is attached to an exhaust gas treatment device with at least one first catalyst and a second catalyst. Additionally, the assembly has the following: a first lambda sensor in a first removal line, wherein the first removal line is designed to remove a part of the exhaust gas upon entering the first catalyst and conduct same back into the exhaust gas treatment device after the exhaust gas passes the first lambda sensor, and the first lambda sensor and at least one part of the first removal line are arranged outside of the exhaust gas treatment device; and a second lambda sensor in a second removal line, wherein the second removal line is designed to remove a part of the exhaust gas between the first catalyst and the second catalyst and conduct same back into the exhaust gas treatment device after the exhaust gas passes the second lambda sensor, and the second lambda sensor and at least one part of the second removal line are arranged outside of the exhaust gas treatment device.

Systems and methods determining a presence or absence of engine misfire at low engine load are disclosed. In one example, the presence or absence of engine misfire is based on a fuel target error value and an exhaust temperature error. Operation of an engine may be adjusted when engine misfire is detected.

The present invention suppresses the worsening of stability due to a variation in EGR amounts between cylinders in a spark ignition engine. An engine control device for controlling a spark ignition engine equipped with an EGR means for recirculating exhaust gas in a combustion chamber and an air-fuel-ratio detection means for detecting the air-fuel ratio in each cylinder, the engine control device being characterized by being equipped with a means for changing the parameters for ignition control of a rich cylinder, when the air-fuel ratio of cylinders varies and there are richer cylinders and leaner cylinders relative to a prescribed air-fuel ratio during the execution of exhaust gas recirculation by the EGR means.

A method and device for controlling a supercharged internal combustion engine is disclosed. An oxygen charge of a catalytic converter of the internal combustion engine is determined. A valve overlap of the internal combustion engine is increased from a lower valve overlap value to an upper valve overlap value. Increasing the valve overlap and/or for at least one phase of the increase, a control value for increasing an air-fuel ratio in at least one cylinder of the internal combustion engine is reduced as a function of the determined oxygen charge.

Methods and systems are provided for estimating a PCV flow to an engine based on the output of an exhaust gas oxygen sensor. During DFSO conditions, a reference voltage of the sensor is modulated initially with an intake throttle open and then with the intake throttle closed. PCV flow leaking past the piston valves in an aging engine, as well as an ambient humidity estimate, are inferred based on the outputs of the sensor during the modulating with the intake throttle open and closed.

A gas concentration detection device for detecting a gas concentration using a limiting current type gas concentration sensor. In an application voltage line set to pass through a plurality of limiting current regions for different values of gas concentration, a ratio for lean is set as a ratio of change in current with respect to a change in voltage when an air/fuel ratio corresponding to the gas concentration is lean, and a ratio of rich different from the ratio for lean is set when the air/fuel ratio is rich.

An air-fuel ratio control controls an air-fuel ratio (air-fuel ratio of an engine) of a mixture supplied to the engine, based on an output value of the downstream-side air-fuel ratio sensor disposed downstream of a catalyst. That is, the air-fuel ratio control apparatus sets the air-fuel ratio of the engine at a rich air-fuel ratio when the output Voxs is smaller than a reference value VREF (when a rich request is occurring). The air-fuel ratio control apparatus sets the air-fuel ratio of the engine at a lean air-fuel ratio when the output Voxs is larger than a reference value VREF (when a lean request is occurring). The air-fuel ratio control apparatus makes the target value VREF gradually come closer to a reference value VF (stoichiometric air-fuel ratio corresponding value) from a certain value, when the output value Voxs deviates greatly from the reference value Vf (points P1-P3).

A method comprising adjusting a fuel injection amount based on a fractional oxidation state of a catalyst, the fractional oxidation state based on reaction rates of grouped oxidant and reductant exhaust gas species throughout a catalyst and a low-dimensional physics-based model derived from a detailed two-dimensional model to obtain a one-dimensional model averaged over time and space that accounts for diffusion limitations in the washcoat and accurately predicts emissions during cold start.

An engine test method includes generating a test pattern in which a plurality of manipulated variables used for an engine test change in chronological order, correcting the test pattern based on an excess air ratio, and performing an engine test using the corrected test pattern to acquire time-series data on the manipulated variables and controlled amounts of the manipulated variables.