Methods of improving SCR performance in heavy duty vehicles may use multiple interdependent control techniques to increase engine exhaust temperatures in a fuel efficient manner. One method combines cylinder deactivation and mechanical loading of an engine by an electrical generator used to input energy into an exhaust stream to manipulate the exhaust temperature through the combined effect of modified air-to-fuel ratio and supplemental energy input. In particular, cylinder deactivation may be used to modify the engine air flowrate and the electric generator may be used to apply mechanical load on the engine to manipulate the engine fuel flow rate to control the engine air-to-fuel ratio and thereby increase exhaust temperatures. The exhaust temperatures may be further increased by using the electrical generator to add the energy generated as input energy to the exhaust stream.

The invention relates to an internal combustion engine system (100), comprising: —an internal combustion engine (2) comprising a cylinder block (3) housing a plurality of cylinders (4), a first intake manifold (6a) connected to a first group of cylinders (4a) a second distinct intake manifold (6b) connected to a second group of cylinders (4b) and a first, respectively a second, exhaust manifold (8a, 8b) for receiving the exhaust gas emitted from the first, respectively the second, group of cylinders (4a, 4b); —an air inlet line (10); —an EGR line (20) connected to the first and second exhaust manifolds (8a, 8b); wherein the internal combustion engine system is operable in at least two operating modes, respectively a normal operating mode in which all cylinders are supplied with fuel and a regeneration operating mode, in which the cylinders of the first group of cylinders (4a) are no longer supplied with fuel, characterized in that: —the system also includes a mixing unit (30) comprising a four-way valve, said four-way valve (30) having a first inlet (31) connected to the EGR line (20), a second inlet (32) connected to the air inlet line (10), a first outlet (33) connected to the first intake manifold (6a) and a second outlet (34) connected to the second intake manifold (6b); —the four-way valve is designed so that, in said normal operating mode, the intake gases supplied to the first intake manifold (6a) and to the second intake manifold (6b) have approximately the same proportion of exhaust gas and so that, in said regeneration operating mode, the intake gas supplied to the first intake manifold (6a) only includes exhaust gas.

Methods of improving SCR performance in heavy duty vehicles may use multiple interdependent control techniques to increase engine exhaust temperatures in a fuel efficient manner. One method combines cylinder deactivation and mechanical loading of an engine by an electrical generator used to input energy into an exhaust stream to manipulate the exhaust temperature through the combined effect of modified air-to-fuel ratio and supplemental energy input. In particular, cylinder deactivation may be used to modify the engine air flowrate and the electric generator may be used to apply mechanical load on the engine to manipulate the engine fuel flow rate to control the engine air-to-fuel ratio and thereby increase exhaust temperatures. The exhaust temperatures may be further increased by using the electrical generator to add the energy generated as input energy to the exhaust stream.

A system and method for a variable displacement internal combustion engine using different types of pneumatic cylinder springs on skipped working cycles to control engine and aftertreatment system temperatures are described. The system and method may be used to rapidly heat up the aftertreatment system(s) and/or an engine block of the engine following a cold start by using one or more different types of pneumatic cylinder springs during skipped firing opportunities. By rapidly heating the aftertreatment system(s) and/or engine block, noxious emissions such as hydrocarbons, carbon monoxide, NO.sub.x and/or particulates, following cold starts are significantly reduced.

Engine controllers and control schemes that facilitate skip fire engine operation in conjunction with use power take-off devices are described. In one aspect, a skip fire mode is exited when the power take-off unit is engaged and the current torque request exceeds a torque threshold. In some embodiments, the exit is delayed when the temperature of an after treatment system is below a designated temperature threshold. In another aspect, the engine transitions to the skip fire mode when the power take-off unit disengages. In some embodiments, exiting is conditioned on the current torque request being less than a torque threshold. In some embodiments, the transition is made immediately, whereas in others the transition only occurs when the power take-off unit is not reengaged for a period of time or is further conditioned on determining that the power take-off unit is likely to remain disengaged for the period of time.

A control method is performed to control a traction device of a motor vehicle having an internal combustion engine that includes a plurality of cylinders. Each of cylinders has at least one air intake valve, at least one exhaust valve for the combustion gases generated by the internal combustion engine, and a fuel injector. A treatment device is provided for the combustion gases that is active from an actuation temperature. The treatment device is placed downstream of the exhaust valve. The traction device includes an electrical heater for heating the combustion gas treatment device. The traction method further compares a temperature of the combustion gas treatment device with an actuating threshold temperature and actuates the electrical heater and stopping a fuel supply being supplied to one or more of the cylinders as long as the temperature of the combustion gas treatment device is below the actuating threshold temperature.

A method and system for monitoring an exhaust gas sensor coupled in an engine exhaust is provided. In one example, the method adjusts an estimate of an exhaust gas oxygen sensor delay time based on a fuel injection ramping time. The fuel injection ramping time compensates for fuel that is injected to the engine while the engine enters or exits a fuel cut-off mode.

Methods of improving SCR performance in heavy duty vehicles may use multiple interdependent control techniques to increase engine exhaust temperatures in a fuel efficient manner. One method combines cylinder deactivation and mechanical loading of an engine by an electrical generator used to input energy into an exhaust stream to manipulate the exhaust temperature through the combined effect of modified air-to-fuel ratio and supplemental energy input. In particular, cylinder deactivation may be used to modify the engine air flowrate and the electric generator may be used to apply mechanical load on the engine to manipulate the engine fuel flow rate to control the engine air-to-fuel ratio and thereby increase exhaust temperatures. The exhaust temperatures may be further increased by using the electrical generator to add the energy generated as input energy to the exhaust stream.

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.