A method for heating a catalytic converter in an exhaust system of an internal combustion engine, in which an exhaust gas burner for heating the catalytic converter is arranged, upstream of the catalytic converter. A lambda probe for controlling the combustion air ratio of the exhaust gas burner is arranged immediately downstream of the exhaust gas burner and upstream of the catalytic converter. The method includes operating the internal combustion engine with a stoichiometric combustion air ratio (λ.sub.E=1), activating the exhaust gas burner, which is operated alternately with a substoichiometric combustion air ratio (λ.sub.B<1) and a superstoichiometric combustion air ratio (λ.sub.B>1), wherein from the substoichiometric combustion air ratio (λ.sub.B<1) to the superstoichiometric combustion air ratio (λ.sub.B>1) as soon as a rich breakthrough is detected by the second lambda probe (34), and wherein a switchover from the superstoichiometric combustion air ratio (λ.sub.B>1) to the substoichiometric combustion air ratio (λ.sub.B<1) takes place as soon as a lean breakthrough is detected by the second lambda probe.

The present disclosure relates to internal combustion engines. The teachings thereof may include monitoring a secondary air system with which secondary air is introduced into exhaust of the internal combustion engine wherein individual cylinders of the internal combustion engine are associated with one of at least two cylinder banks and a separate exhaust duct is associated with each cylinder bank. The methods may include delivering secondary air with a compression arrangement via a common secondary air line divided into a number of individual secondary air sublines corresponding to the number of exhaust ducts at a branching point downstream of the compression arrangement; controlling the secondary air to simultaneously enable or inhibit the flow to the individual secondary air sublines; detecting values for the pressure downstream of the compression arrangement and upstream of the branching point; detecting pulsations of a pressure in each cylinder bank when the compression arrangement is activated and the throughflow control arrangement set into the open state; summing the pulsations; comparing each of summed-up values with threshold values; and if the respective threshold value is exceeded, identifying a fault in the throughflow control arrangement.

A vehicle and method reduce heating of a particulate filter during a regeneration event in response to an accelerator pedal tip-out and particulate filter temperature exceeding or anticipated to exceed a threshold by fueling the engine to reduce oxygen in the exhaust flowing to the particulate filter. An electric machine may be operated as a generator charging a battery to compensate or offset torque produced by the fueling of the engine. The current or anticipated particulate filter temperature may be estimated by a soot combustion model for a current regeneration event and/or a future regeneration event based on soot loading of the particulate filter.

When the air fuel ratio dither control is carried out, an air fuel ratio of a mixture in each of one or more lean cylinders and one or more rich cylinders is controlled in a feedback manner based on an average value of a detected value of an air fuel ratio sensor, so that an average value of an air fuel ratio of exhaust gas flowing into the three-way catalyst becomes a predetermined target exhaust gas air fuel ratio. At this time, the air fuel ratio dither control is carried out, by setting at least a cylinder with the highest gas impingement intensity in a cylinder group of an internal combustion engine as the one or more lean cylinders.

The present subject matter relates to a method and a treatment system monitor for monitoring an engine exhaust after-treatment system containing more than one Lean NO.sub.x Traps (LNT). The method includes receiving an exhaust gas of a desired air-fuel ratio upstream of a respective LNT. The LNT is further regenerated using a richer than stoichiometric exhaust air-fuel ratio and subsequently an air-fuel ratio received downstream of the LNT is evaluated. Further, a working state of a respective LNT is determined based on the monitoring of the air-fuel ratio and oxygen level upstream and downstream of the LNT.

A control device is configured to execute a process of calculating an increase amount of deterioration obtained by subtracting from a first degree of deterioration that is a degree of deterioration of the three-way catalyst during execution of the oxygen supply process a second degree of deterioration that is a degree of deterioration of a three-way catalyst in a case where an oxygen supply process of supplying oxygen to an exhaust passage is assumed not to be executed, a process of calculating an integrated value of the increase amount of deterioration, and a process of executing a deterioration reduction process of reducing a rate of deterioration of the three-way catalyst in a case where the calculated integrated value is equal to or larger than a first determination value.

An exhaust aftertreatment system for purifying an exhaust gas feedstream that is expelled from an internal combustion engine that is operable at an air/fuel ratio that is lean of stoichiometry is described. The exhaust aftertreatment system includes a barrier discharge plasma reactor that is disposed upstream relative to a catalytic reactor and electrically connected to a plasma controller. The barrier discharge plasma reactor is controlled to generate ozone from constituents of the exhaust gas feedstream when the internal combustion engine is operating at a lean air/fuel ratio and at a low temperature condition. The generated ozone reacts, in the catalytic reactor, to oxidize non-methane hydrocarbons contained in the exhaust gas feedstream when the internal combustion engine is operating at lean air/fuel ratio and at low temperature conditions.

During execution of a first purification process of fluctuating a hydrocarbon concentration in exhaust gas flowing into a first catalyst with an amplitude within a prescribed range at a time interval within a prescribed range, when a switch request to a second purification process of purifying NOx in a second catalyst by adding urea water into the exhaust gas is generated, the switch to the second purification process is prohibited on the condition that a current NOx purification rate (a first purification rate R1) is higher than a purification rate (a second purification rate R2) on the assumption that the second purification process is executed, and an HC poisoning recovery stand-by process of reducing an additive amount of hydrocarbon per once in the first purification process is executed so as to reduce a slip amount of hydrocarbon into the downstream of the first catalyst.

Methods and systems are provided for operating a cylinder of an engine including a pre-chamber ignition system during a cold start condition. In one example, a method may include performing a post-injection in the cylinder, and then performing a pre-chamber combustion during an exhaust stroke of the cylinder. In this way, a temperature of a catalyst of the engine may be increased, which may decrease vehicle emissions during the cold start condition.

A gaseous fuel engine system includes an exhaust controller coupled with a temperature sensor and a NOx sensor, and structured to actuate open an electrically actuated bypass valve to bypass an oxidation catalyst with exhaust, based on an exhaust temperature and an exhaust NOx amount to mitigate production of yellow smoke. Yellow smoke mitigation logic may run during startup and when the gaseous fuel engine is in a lower part of an engine load range. The yellow smoke mitigation logic can be selectively triggered in response to transient engine load increases when the gaseous fuel engine is operating in an upper part of an engine load range.