A method for the onboard diagnosis in a vehicle having a catalytic convertor and a lambda-controlled internal combustion engine in the running operation of the vehicle, includes determining the currently maximum possible oxygen storage capacity of the catalytic convertor as well as a measured temporal duration between the lean spike of the pre-catalyst lambda probe and the post-catalyst lambda probe takes place by means of an OSC diagnosis. The method also includes determining a theoretical residual oxygen content and determining a theoretical temporal duration. When the quotient between the measured temporal duration (Δt) and the theoretical temporal duration (Δt.sub.theo) lies within a predefined range delimited by a first and a second threshold value (SW1; SW2), thus: $\mathrm{SW}1\le \frac{\Delta t}{\Delta t_{\mathrm{theo}}}\le \mathrm{SW}2,$
it is determined that the pre-catalyst lambda probe and the post-catalyst lambda probe operate without flaw.

A state estimation apparatus includes: a rate calculating configured to calculate, based on both a flow rate and an air-fuel ratio of exhaust gas flowing into an oxygen storage catalyst, a rate of change in an oxygen storage amount in the oxygen storage catalyst; a limit calculating unit configured to calculate a limit rate which is a limit value for the rate of change; and a storage-amount updating unit configured to update, based on the rate of change and the limit rate, an estimated value of the oxygen storage amount. Moreover, the storage-amount updating unit is further configured to: update, when the rate of change does not exceed the limit rate, the estimated value based on the rate of change; and update, when the rate of change exceeds the limit rate, the estimated value based on the limit rate.

A controller for an internal combustion engine includes processing circuitry that executes a richening process until an exhaust sensor detects exhaust gas having a rich air-fuel ratio. The processing circuitry executes an air supplying process to supply a catalytic converter with air until the exhaust sensor detects that the exhaust gas has a lean air-fuel ratio. The processing circuitry cumulates the amount of air supplied to the catalytic converter until the exhaust sensor detects that the exhaust gas has a lean air-fuel ratio in the air supplying process. The air supplying process includes stopping fuel supplied to the one or more of the cylinders and performing combustion at an air-fuel ratio that is less than or equal to the stoichiometric air-fuel ratio in the remaining one or more of the cylinders.

An engine control device performs air-fuel ratio control of an engine through a main air-fuel ratio feedback process based on an output of a front air-fuel ratio sensor, a sub air-fuel ratio feedback process of alternately switching a target air-fuel ratio between a lean-side target air-fuel ratio and a rich-side target air-fuel ratio based on an output from a rear air-fuel ratio sensor. The engine control device performs a limiting process of setting an upper limit of a control range of an opening level of a waste gate valve to be less when a combustion operation of the engine continues to be performed for a long time without being stopped by fuel cutoff than otherwise.

A controller for an internal combustion engine includes processing circuitry that executes a richening process until an exhaust sensor detects exhaust gas having a rich air-fuel ratio. The processing circuitry executes an air supplying process to supply a catalytic converter with air until the exhaust sensor detects that the exhaust gas has a lean air-fuel ratio. The processing circuitry cumulates the amount of air supplied to the catalytic converter until the exhaust sensor detects that the exhaust gas has a lean air-fuel ratio in the air supplying process. The air supplying process includes stopping fuel supplied to the one or more of the cylinders and performing combustion at an air-fuel ratio that is less than or equal to the stoichiometric air-fuel ratio in the remaining one or more of the cylinders.

An engine control device performs air-fuel ratio control of an engine through a main air-fuel ratio feedback process based on an output of a front air-fuel ratio sensor, a sub air-fuel ratio feedback process of alternately switching a target air-fuel ratio between a lean-side target air-fuel ratio and a rich-side target air-fuel ratio based on an output from a rear air-fuel ratio sensor. The engine control device performs a limiting process of setting an upper limit of a control range of an opening level of a waste gate valve to be less when a combustion operation of the engine continues to be performed for a long time without being stopped by fuel cutoff than otherwise.

To keep catalyst purification efficiency high and prevent deterioration of emission performance. Therefore, an internal combustion engine control device according to an aspect of the present invention includes: an oxygen storage ratio calculation unit that calculates an oxygen storage ratio of a catalyst based on a catalytic reaction model having at least a detection value of a first exhaust gas sensor disposed on an upstream side of the catalyst as an input; a statistical model calculation unit that predicts a catalyst downstream exhaust gas concentration using a statistical model having an oxygen storage ratio as an input and a catalyst downstream exhaust gas concentration as an output; and an air-fuel ratio correction amount calculation unit that calculates an air-fuel ratio correction amount of an air-fuel mixture of an internal combustion engine based on a future catalyst downstream exhaust gas concentration calculated by the statistical model calculation unit.

A catalyst having an oxygen storage capacity is provided in an exhaust passage of an internal combustion engine. A catalyst temperature calculating device calculates an oxygen storage amount of the catalyst to a value greater than or equal to zero and less than or equal to than a maximum value based on an amount of oxygen and an amount of unburned fuel components in a fluid flowing into the catalyst. A temperature calculation process calculates a temperature of the catalyst assuming that an amount of temperature rise of the catalyst is larger when an increase amount of the oxygen storage amount is large than when the increase amount of the oxygen storage amount is small in a case where the oxygen storage amount increases.

Methods and systems are provided for increasing a temperature of a catalyst of an engine by operating the engine in a split lambda catalyst heating mode. In one example, a method may include, while operating an engine in a split lambda catalyst heating mode, adjusting a magnitude of a lambda split between a rich set of combustion events and a lean set of combustion events based on soot formation in the rich set of combustion events. In this way, catalyst temperature may be increased while maintaining engine efficiency and preventing soot formation in the cylinders.

Methods and systems are provided for increasing a temperature of a catalyst of an engine by operating the engine in a split lambda catalyst heating mode. In one example, a method may include, while operating an engine in a split lambda catalyst heating mode, adjusting a magnitude of a lambda split between a rich set of combustion events and a lean set of combustion events based on soot formation in the rich set of combustion events. In this way, catalyst temperature may be increased while maintaining engine efficiency and preventing soot formation in the cylinders.