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.

An air injection system for an engine includes an exhaust flange formed in a cylinder head integrated with an exhaust manifold, wherein the exhaust manifold is coupled to the exhaust flange, an air injection nozzle provided on the cylinder head or the exhaust manifold, a valve configured to control air supplied to the air injection nozzle, and a controller configured to control the valve, wherein the controller is configured to control the valve and inject air through the air injection nozzle when an exhaust-gas temperature reaches a predetermined combustion temperature in an initial start stage of the engine.

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.

In one aspect, an aspiration system for a work vehicle includes an exhaust tube extending along a flow direction from an upstream end to a downstream end. The exhaust tube defines an exhaust passage extending from the upstream end of the exhaust tube to the downstream end of the exhaust tube. The exhaust tube includes a venturi portion. The aspiration system also includes an aspiration tube in flow communication with the venturi portion and configured to receive an aspirated airflow. The system further includes a flow adjustment mechanism provided in operative association with venturi portion such that the flow adjustment mechanism is configured to adjust a cross-sectional flow area of the venturi portion of the exhaust tube.

A method is disclosed for operating an internal combustion engine which comprises a primary air system for providing fresh air and a secondary air system. The secondary air system is configured to branch off secondary air from the primary air system and blow it into an exhaust gas duct. The secondary air system has a compressor for feeding the secondary air and a secondary air valve for shutting off or enabling the blowing in of secondary air. The method includes (i) activating the compressor while the secondary air valve is kept closed, (ii) determining whether compressor surging is occurring or is directly imminent, (iii) sensing at least one sensor signal if compressor surging is occurring or is directly imminent, and (iv) determining whether there is a leak in the secondary air system, on the basis of the sensed sensor signal.

A method is disclosed for operating an internal combustion engine which comprises a primary air system for providing fresh air and a secondary air system. The secondary air system is configured to branch off secondary air from the primary air system and blow it into an exhaust gas duct. The secondary air system has a compressor for feeding the secondary air and a secondary air valve for shutting off or enabling the blowing in of secondary air. The method includes (i) activating the compressor while the secondary air valve is kept closed, (ii) determining whether compressor surging is occurring or is directly imminent, (iii) sensing at least one sensor signal if compressor surging is occurring or is directly imminent, and (iv) determining whether there is a leak in the secondary air system, on the basis of the sensed sensor signal.

An EHC line leakage diagnosis method can operate a heater of an oxygen detector when satisfying one or more conditions of an engine off time, a coolant temperature, and an outside air temperature by a diagnosis controller upon the key-on of the non-operation of an engine, and then, determine the normality or abnormality of a temperature drop using a change in a temperature value of a signal value and the temperature value detected by the oxygen detector after an air pump is driven, and then confirm the leakage of an exhaust line and a line on the rear end portion of an EHC valve of an air line using the number of times of the occurrence of the abnormality of the temperature drop, and can perform the failure diagnosis without generating the exhaust gas by not operating an engine.

A method for the diagnosis of an air supply circuit supplying air to a burner of an exhaust gas after-treatment system for an exhaust system of an internal combustion engine, wherein the air supply circuit is provided with a pumping device housed along a first duct adjusted by a shut-off valve. The method entails housing a first pressure sensor along the first duct interposed between the pumping device and the burner; housing a second pressure sensor along a second duct out of the burner; acquiring the pressure signals detected by said first and second pressure sensors; and diagnosing faults and/or malfunctions in the air supply circuit depending on the pressure signals detected by said first and second pressure sensors.

A method for operating an exhaust gas burner that is situated in an exhaust gas system downstream from an internal combustion engine of a motor vehicle during a start phase of the exhaust gas burner, in which the internal combustion engine is not fired. The method includes an incremental increasing of the air mass flow supplied to the exhaust gas burner and an incremental varying of a fuel mass flow supplied to the exhaust gas burner.

The disclosure relates to a method and a device for diagnosing coking of a secondary air system of an internal combustion engine. The secondary air system has an intake air line for providing secondary air, a secondary air pump for compressing the secondary air, a secondary air valve for controlling the secondary air injection, a pressure sensor that is arranged in the secondary air system downstream of the secondary air pump and upstream of the secondary air valve, and an injection line for injecting the secondary air into an exhaust tract of the internal combustion engine.