A process for testing a plurality of components of an exhaust gas aftertreatment system (100) is disclosed, wherein the plurality of components comprises a first SCR catalyst and at least one further SCR catalyst arranged downstream of the first SCR catalyst in the flow direction of exhaust gas to be passed through the exhaust gas aftertreatment system, a first NOx sensor assigned to the first SCR catalyst and at least one further NOx sensor and a first DeNOx element assigned to the first SCR catalyst and at least one further DeNOx element and wherein the process comprises at least the following steps: conditioning the SCR catalysts, testing the NOx sensors, testing the DeNOx systems testing a storage capacity for the reductant of the SCR catalysts.

A system has a pump and an injector coupled to the pump. The system further comprises a controller coupled to the pump and the injector. The controller is structured to: determine a change of reductant flow relative to a change of pump rate of the pump; and generate a status command indicative of at least one of an under-restricted injector or an over-restricted injector in response to the determination of the change of reductant flow relative to the change of pump rate of the pump.

A system for controlling emissions of a motor-vehicle spark-ignition internal combustion engine includes first and second exhaust gas treatment devices and a secondary air feeding system for feeding secondary air into an exhaust gas conduit, between the first and second exhaust gas treatment devices. The secondary air feeding system is activated only when engine load is greater than a predetermined load value and/or when engine rotational speed is greater than a predetermined speed value. In this condition, an air/fuel ratio of the engine is kept at a value lower than the stoichiometric value, so as to feed the engine with a rich mixture. In one example, an electronic controller is configured for controlling activation of the secondary air feeding system on the basis of a map, as a function of values of the engine load and rotational speed. The map is predetermined depending upon specific characteristics of the engine.

The invention relates to a regeneration air system for an exhaust aftertreatment system of an internal combustion engine and to such an exhaust aftertreatment system. The regeneration air system comprises a regeneration air delivery element, a regeneration air duct, and a regeneration air valve. A sensor system is provided in the regeneration air duct with which a regeneration air mass flow {dot over (m)}.sub.SL can be determined exactly. The exhaust aftertreatment system comprises an exhaust system with an exhaust duct in which, in the direction of flow of an exhaust gas through the exhaust duct, a three-way catalytic converter is arranged underhood and a four-way catalytic converter is arranged downstream. A provision is made that an intake point for the regeneration air from the regeneration air system is formed on the exhaust duct downstream from the underhood three-way catalytic converter and upstream from the four-way catalytic converter.

A process for detecting reductant deposits includes accessing data indicative of signal output from a radiofrequency sensor positioned proximate a decomposition reactor tube; comparing the data indicative of signal output from the radiofrequency sensor to a deposit formation threshold; and activating a deposit mitigation process responsive to the data indicative of signal output from the radiofrequency sensor exceeding the deposit formation threshold.

An aftertreatment system includes an exhaust reductant tank configured to store an exhaust reductant. A filter is fluidically coupled to the exhaust reductant tank. The aftertreatment system includes a hydrocarbon detection device configured to indicate the presence of a hydrocarbon in the exhaust reductant. A catalyst is included in the system and configured to treat the exhaust reductant flowing through the system. The hydrocarbon detection device can include a hydrophobic paper, and can be disposed in the filter.

An internal combustion engine comprises a filter and is configured to enable attachment of a secondary air feed system feeding air into exhaust gas flowing into the filter. A control device of the engine is configured, in the PM removal control for removing particulate matter deposited on the filter, to perform temperature raising processing for controlling the engine so that the air-fuel ratio of the exhaust gas discharged from the engine body 1 is a rich air-fuel ratio and for feeding air from the secondary air feed system, and to perform regeneration processing for controlling the engine so that the air-fuel ratio of the exhaust gas discharged from the engine body is a stoichiometric air-fuel ratio and for feeding air from the secondary air feed system so that the air-fuel ratio of the exhaust gas flowing into the filter is a lean air-fuel ratio.

An exhaust purification system for the reduction of emissions from an exhaust stream, including an oxygen detection system; a catalyst; and an air injection system positioned between the oxygen detection system and the catalyst to inject air into the exhaust stream at designated exhaust conditions, to protect the catalyst from oxygen-deprived conditions.

The invention relates to a method for exhaust gas aftertreatment in an internal combustion engine. For purposes of the exhaust gas aftertreatment in the internal combustion engine, an exhaust gas system is provided in which a first three-way catalytic converter is arranged, as seen in the direction in which the exhaust gas of the internal combustion engine flows through the exhaust gas system, while at least another three-way catalytic converter is arranged downstream from the first three-way catalytic converter. Here, at least one lambda probe is arranged in an exhaust gas channel of the exhaust gas system upstream from the appertaining three-way catalytic converters. In the proposed method, a component temperature of the three-way catalytic converters is determined and compared to a light-OFF temperature. In this process, the lambda control of the internal combustion engine is carried out by means of the lambda probe upstream from the last three-way catalytic converter that has reached its light-OFF temperature. Moreover, according to the invention, an exhaust gas aftertreatment system for carrying out such a method is being proposed.

An exhaust gas control apparatus includes an exhaust gas control catalyst disposed in an exhaust passage, a filter disposed downstream of the catalyst, a secondary air supply device configured to supply secondary air into exhaust gas flowing into the filter at a location downstream of the catalyst in an exhaust gas flow direction, and an electronic control unit. The electronic control unit is configured to, when a temperature of the catalyst is higher than or equal to an activation temperature and an air-fuel ratio of exhaust gas emitted from an engine body is a rich air-fuel ratio, cause the supply device to supply secondary air into exhaust gas while periodically increasing or reducing the air such that the air-fuel ratio of exhaust gas flowing into the filter alternately varies between rich and lean air-fuel ratios.