An emissions control system for a motor vehicle that includes an internal combustion engine includes a first selective catalytic reduction (SCR) device and a reductant injector, The system further includes a model-based controller that is configured to calculate a target amount of reductant to inject to maintain a predetermined ratio between an amount of NH3 and an amount of NOx at the outlet of the first SCR device, and to send a command for receipt by the reductant injector to inject the calculated amount of reductant. The model-based controller is further configured to send a command for receipt by an engine controller to influence NOx production by the engine by modifying an engine operating parameter, based on a calculated target amount of NOx at the inlet of the first SCR device.

Methods and systems are provided for monitoring a NOx storage capacity of a passive NOx adsorption catalyst (PNA) included in an exhaust gas after-treatment system of an engine. In one example, a method may include, after an engine cold start and prior to an exhaust gas temperature reaching an upper threshold temperature, indicating degradation of the PNA based on an amount of NOx measured downstream of the PNA during a fuel cut event and while the exhaust gas temperature is between a lower threshold temperature and the upper threshold temperature. In this way, degradation of the NOx storage capacity may be inferred based on an amount of NOx released from the PNA and independent of a NOx storage measurement.

Rich spike is carried out in an efficient manner. In an exhaust gas purification apparatus for an internal combustion engine which performs lean burn operation, the apparatus includes an NOx storage reduction catalyst, a controller to carry out rich spike, to calculate a storage amount of NOx, to calculate a storage amount of nitrates, and calculate a nitrate ratio, wherein the controller controls a timing at which the rich spike is carried out, based on the nitrate ratio.

An engine control device is provided, which includes an oxidation catalyst provided in an exhaust passage to oxidize unburned fuel within exhaust gas, a NO.sub.x catalyst provided integrally with or downstream of the oxidation catalyst, a PM filter provided in the exhaust passage downstream of the oxidation catalyst to capture fine particulate matter within the exhaust gas, a fuel injector, and a controller. When the particulate matter is accumulated by a given amount, the controller starts a PM filter regeneration control to remove the particulate matter, and after this control is started and when the accumulation amount decreases by a given amount, the controller starts a NO.sub.x catalyst regeneration control to switch between a first state in which an air-fuel ratio of the exhaust gas is a stoichiometric air-fuel ratio or less and a second state in which the air-fuel ratio is higher than the stoichiometric air-fuel ratio.

In some examples, a system including one or more processors may receive sensor data from one or more sensors indicating one or more engine parameters of an engine including a combustion chamber. Based on the sensor data, the system may determine a homogeneity index indicative of a homogeneity of an air-fuel mixture within the combustion chamber. Furthermore, the system may determine an estimated amount of NOx in the exhaust gas based at least in part on the homogeneity index. In addition, based at least partially on the estimated amount of NOx in the exhaust gas, the system may send an instruction to control an engine component.

A control system for fuel injection by predicting engine noise may include an engine noise predicting device configured to derive a predicted engine noise value in real time by a predicted engine noise coefficient which is pre-stored according to a currently measured combustion pressure value of an engine; and a combustion controller configured to determine a difference between the real-time predicted engine noise value derived by the engine noise predicting device and a target engine noise value for a current operation condition of the engine, and when the engine noise is determined as being degraded due to an abnormal combustion, configured to change the target engine noise value to control fuel injection according to the changed target engine noise value.

Methods and systems are provided for an exhaust aftertreatment arrangement. In one example, a system includes a LNT upstream of an SCR with an oxygen storage component arranged therebetween, and where a rich operation of an engine is limited based on an oxygen load of the oxygen storage component when an exhaust gas temperature is higher than a limit temperature.

An exhaust gas purification apparatus for an internal combustion engine includes: a controller comprising at least one processor is configured to carry out rich spike; wherein the controller carries out supply control to supply a reducing agent to a post-stage catalyst, wherein in cases where a temperature of an NSR catalyst becomes less than a predetermined determination temperature in at least a part of a determination period of time, the controller carries out the supply control according to the execution of current rich spike; wherein the controller controls such that in cases where the storage amount of NOx is the same, an amount of supply of the reducing agent in the supply control is made larger as a period of time in which the temperature of the NSR catalyst becomes less than the predetermined determination temperature in the determination period of time becomes longer.

An exhaust purification system includes a NOx-occlusion-reduction-type catalyst that occludes NOx in exhaust in a lean state and reduces and purifies the occluded NOx in exhaust in a rich state, and a NOx purge rich control unit that executes NOx purge of reducing and purifying the occluded NOx by putting the exhaust into the rich state by fuel injection control, where a catalyst temperature of the NOx-occlusion-reduction-type catalyst is equal to or higher than a catalyst temperature threshold value and a NOx occlusion amount of the NOx-occlusion-reduction-type catalyst is equal to or higher than an NOx occlusion amount threshold value, and executes the NOx purge when the catalyst temperature is lower than a catalyst temperature threshold value.

An exhaust purification system is provided with a NOx-occlusion-reduction-type catalyst and a NOx purge rich control unit that executes NOx purge of reducing and purifying the occluded NOx by putting the exhaust into a rich state by fuel injection control, in a case where a catalyst temperature of the NOx-occlusion-reduction-type catalyst is equal to or higher than a catalyst temperature threshold value and a NOx occlusion amount of the NOx-occlusion-reduction-type catalyst is equal to or higher than an NOx occlusion amount threshold value, and executes the NOx purge even when the NOx occlusion amount is less than the NOx occlusion amount threshold value, in a case where the catalyst temperature is equal to or higher than a catalyst temperature threshold value which is greater than the catalyst temperature threshold value.