A multi-cylinder internal combustion engine is configured to perform an all-cylinder operation and a partial-cylinder operation. The ignition timing controller executes a process that sets a knock control amount and a knock learning value, a process that determines whether knocking is occurring, a process that updates a value of the knock control amount in accordance with whether knocking is occurring, a process that updates the knock learning value such that the knock learning value gradually approaches a knock control operated amount, a process that operates ignition timing of each cylinder based on the knock control amount and the knock learning value, and a process that limits update of the knock learning value such that a followability of the knock learning value to the knock control operated amount is lower during the partial-cylinder operation than during the all-cylinder operation.

A method for exhaust temperature management in a multiple-cylinder, reciprocating-piston engine, comprising sensing a low temperature condition of the exhaust and implementing an increased heat output engine cycle pattern for the engine based on the sensed low temperature condition. The increased heat output engine cycle pattern comprises deactivating fuel injection to a first cylinder of the engine, the first cylinder comprising a piston reciprocating between top-dead-center and bottom-dead-center. Also, activating engine braking mode on the first cylinder by opening one or more valves when the piston is away from bottom-dead-center during a compression stroke. A second cylinder of the engine is fired in a combustion mode while the first cylinder is in engine braking mode.

The invention concerns a method for controlling regeneration of an exhaust gas aftertreatment system (7, 8) of an internal combustion engine (4) arranged on a vehicle (1), wherein the vehicle (1) is provided with a control system configured to control the regeneration in at least a first regeneration strategy mode comprising a first set of predetermined actions to be taken for controlling initialization and performance of regeneration processes. The method comprises the steps of: (100)—adapting the control system so as to be configured to alternatively control the regeneration in a second regeneration strategy mode, wherein the second regeneration strategy mode comprises a second set of predetermined actions to be taken for controlling initialization and performance of regeneration processes, and wherein the first and second regeneration strategy modes differ from each other in that the first and second set of predetermined regeneration control actions differ from each other; (200)—collecting, during operation of said vehicle (1) or of another vehicle, data on an exhaust gas regeneration capability of said vehicle (1) or the other vehicle as a function of time; and (300)—evaluating, based on the collected data and the difference between the first and second regeneration strategy modes, whether the first or the second regeneration strategy mode is the most suitable for said vehicle (1) if operating under conditions corresponding to the operational conditions for the vehicle for which data were collected. The invention also concerns a vehicle arranged to be the subject of such a method and to a computer program product, a computer readable medium and a control system related to performance of the steps of the above method.

Methods and systems for operating an engine that includes a controller and a NOx sensor are described. In one example, output of the NOx sensor is selectively made available to software modules within the controller when an offset in NOx sensor output is not expected. If the offset in NOx sensor output is expected, the NOx sensor output may not be made available to the software modules.

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.

Methods and systems are provided for reducing emissions during an engine cold start. In one example, a method may include, during emission control device heating, injecting heated air into an exhaust runner of each cylinder of the engine during an exhaust stroke of the corresponding cylinder, after a blowdown exhaust pulse. In this way, an amount of hydrocarbons in feedgas provided to the emission control device prior to the emission control device reaching its light-off temperature may be reduced.

Methods and systems are provided for an exhaust system. In one example, the exhaust system includes an aftertreatment device and a recirculation passage. A recirculation valve is positioned in the recirculation passage and configured to control an amount of recirculated exhaust gas flowing through the recirculation passage to the aftertreatment device. The exhaust system further includes a diverter valve configured to control a flow of engine exhaust gases to different portions of a catalyst of the aftertreatment device.

Methods and systems are provided for recirculation of an engine exhaust gas. The system includes an engine, an exhaust system configured to channel exhaust gas from the engine to an outlet, an aftertreatment device, an exhaust recirculation system configured to divert at least some of the exhaust gas as recirculated exhaust gas from a first position in the exhaust system downstream of the aftertreatment device, through a housing enclosing the aftertreatment device, and to a second position in the exhaust system upstream of the aftertreatment device, wherein the recirculated exhaust gas is combined with the exhaust gas at the second position, a controller configured to, by a processor, selectively operate the exhaust recirculation system to control the exhaust recirculation system to divert the exhaust gas and thereby cause the recirculated exhaust gas to be treated with the aftertreatment device more than once.

Methods and systems are provided for monitoring a change in exhaust particulate filter (PF) soot load during an engine non-combusting condition. In one example, a method may include, responsive to a higher than threshold PF temperature immediately prior to an engine shutdown, estimating a rate of soot burn when the engine is no longer combusting, and estimating a soot load on the PF during and at an onset of immediately subsequent engine start based in part on the rate of soot burn.

An abnormality detection device for an air-fuel ratio detection device arranged downstream of a filter is equipped with an abnormality detection unit that detects an abnormality in the air-fuel ratio detection device based on output change characteristics of the air-fuel ratio detection device during fuel cutoff control for stopping the supply of fuel to a combustion chamber of an internal combustion engine, and a combustion determination unit that determines whether or not a combustion amount of particulate matter in a filter during fuel cutoff control is larger than a predetermined amount. The abnormality detection unit prohibits detection of an abnormality in the air-fuel ratio detection device when the combustion determination unit determines that the combustion amount is larger than the predetermined amount.