A method for controlling an exhaust after-treatment system based on NO.sub.2 medium adjustment includes the following steps: creating a diesel oxidation catalyst (DOC) reaction map, a diesel particulate filter (DPF) reaction map, and a selective catalytic reduction (SCR) reaction map; obtaining an SCR reaction temperature, desired SCR reaction efficiency, and obtaining NO.sub.2 demand according to the SCR reaction map; obtaining a DPF reaction temperature and differential pressure, and obtaining NO.sub.2 consumption from the DPF reaction map; obtaining NO.sub.2 production, and calculating NO.sub.2 input for SCR; if the NO.sub.2 input is not equal to the NO.sub.2 demand, calculating target NO.sub.2 production, obtaining a target DOC reaction temperature corresponding to the target NO.sub.2 production from the DOC reaction map, and adjusting a fuel injection rate so that the DOC reaction temperature is equal to the target DOC reaction temperature.

Methods and systems for operating an engine that includes an after treatment system are described. In one example, traffic data and navigation system data are a basis for deciding whether or not to increase heat output of an engine to ensure operation of the after treatment system. In particular, one or more actuators may be adjusted to minimize fuel consumption and/or reduce feedgas emissions while generating sufficient heat to maintain after treatment system operation.

A regeneration control apparatus for controlling, in an exhaust gas treatment apparatus of a diesel engine including a diesel oxidation catalyst (DOC) disposed in an exhaust passage of an internal combustion engine and a diesel particulate filter (DPF) disposed downstream of the DOC, execution of forced regeneration to remove an exhaust particulate matter (PM) which accumulates on the DPF through a temperature increase of the DPF, includes: a late-post injection amount determination part which determines a late-post injection amount. The late-post injection amount determination part is configured to determine an upper limit value of the late-post injection amount on the basis of an air excess ratio of exhaust gas flowing into the DOC obtained on the basis of a temperature index of the DOC.

A controller executes a fuel introduction process when stopping combustion in a cylinder under a situation in which a crankshaft is rotating. The fuel introduction process causes a fuel injection valve to inject fuel and causes the fuel to flow out unburned from inside the cylinder to an exhaust passage. The opening degree of an exhaust gas recirculation valve at a point in time when a state in which the execution condition of the fuel introduction process is not satisfied is switched to a state in which the execution condition of the fuel introduction process is satisfied is a preliminary opening degree. During the execution of the fuel introduction process, the recirculation valve controlling section causes the opening degree of the exhaust gas recirculation valve to be smaller than the preliminary opening degree.

Methods and systems are provided for re-combustion of exhaust in a cylinder of a multi-cylinder engine in order to increase the temperature of the exhaust for enhancing catalytic conversion within the multi-cylinder engine. In one example, a method may include expelling combusted gases from the cylinder into an intake manifold via an intake valve during an exhaust stroke, in order to rebreathe in the combusted gases from the intake manifold via the intake valve in a subsequent intake stroke.

A method for controlling the operation of an engine system in a vehicle is provided The engine system includes an engine configured to operate in at least a two-stroke combustion mode and a four-stroke combustion mode, and an exhaust aftertreatment system, EATS configured to reduce emissions from the engine exhausts. The method comprising estimating or predicting the temperature of the EATS; estimating or predicting the emissions out of the EATS; n response of that the temperature of the EATS is below a predetermined temperature threshold, and that the emissions out of the EATS is above a predetermined emission threshold, performing a primary NOx emission reducing activity by operating the engine in a two-stroke combustion mode; subsequently to initiating the operation of the engine in a two-stroke combustion mode, and in response of that the emissions out of the EATS is below the predetermined emission threshold, changing engine operation from the two-stroke combustion mode to a four-stroke combustion mode.

An exhaust gas control apparatus for an internal combustion engine includes: a catalyst disposed in an exhaust passage of the engine and configured to be able to occlude oxygen; an air-fuel ratio sensor that detects an air-fuel ratio of an out-flow exhaust gas; and an air-fuel ratio control device that controls an air-fuel ratio of an in-flow exhaust gas to a target air-fuel ratio. The device executes air-fuel ratio reduction control in which the target air-fuel ratio is set to a rich setting air-fuel ratio, and corrects a parameter related to the air-fuel ratio reduction control such that an amount of a reducing gas supplied to the catalyst is decreased when a minimum air-fuel ratio obtained when the detected air-fuel ratio is varied to a rich side is richer than the rich setting air-fuel ratio or an average value of detected air-fuel ratios of the in-flow exhaust gas.

An exhaust gas control apparatus for an internal combustion engine includes: a catalyst disposed in an exhaust passage of the engine and configured to be able to occlude oxygen; an air-fuel ratio sensor that detects an air-fuel ratio of an out-flow exhaust gas; and an air-fuel ratio control device that controls an air-fuel ratio of an in-flow exhaust gas to a target air-fuel ratio. The device executes air-fuel ratio reduction control in which the target air-fuel ratio is set to a rich setting air-fuel ratio, and corrects a parameter related to the air-fuel ratio reduction control such that an amount of a reducing gas supplied to the catalyst is decreased when a minimum air-fuel ratio obtained when the detected air-fuel ratio is varied to a rich side is richer than the rich setting air-fuel ratio or an average value of detected air-fuel ratios of the in-flow exhaust gas.

System and methods are described for optimizing exhaust flow rate and temperature during specified operational periods warm-up and keep-warm conditions, by minimizing or maximizing heat flux during those specified operational periods.

A method comprises determining that an aftertreatment system is in a cold-operation mode; initiating a low engine-out NOx (LEON) mode by controlling a component of a vehicle containing the aftertreatment system to decrease an instantaneous engine out NOx (EONOx) amount and to increase exhaust energy relative to a normal operation mode for an engine of the vehicle; receiving information indicative of an operating status of the vehicle during the LEON mode; disengaging the LEON mode; subsequent to disengaging the LEON mode, initiating a thermal management (TM) mode for the aftertreatment system, wherein the TM mode is initiated by controlling a component of the vehicle to increase fueling to the engine for a power level by reducing engine efficiency and directing excess fuel to the aftertreatment system; receiving information indicative of an operating status of the vehicle during the TM mode; and disengaging the TM mode.