Aspects of the present invention relate to a valve seat (20) for a poppet valve of an internal combustion engine, wherein the poppet valve comprises a head and a stem behind the head, the valve seat comprising: an aperture (21) configured to form a seal with the head of the poppet valve when the poppet valve is in a closed position; and a peripheral body (22) defining, at least in part, one or more ports (23) shaped like e.g. grooves and sized to enable injection of liquid or gas from a cylinder head of the internal combustion engine into a gas stream behind the head of the poppet valve.

An engine assembly and a method of control thereof is provided. The engine assembly comprises: an exhaust gas aftertreatment device having an inlet for receiving exhaust gases leaving an engine; a heater for selectively heating gases at or upstream of the exhaust gas aftertreatment device; an air moving device for driving a flow of gases into the inlet of the exhaust gas aftertreatment device when the engine is in a non-running condition; and a controller configured to, prior to the engine being started: operate the heater to heat gases at or upstream of the inlet; and operate the air moving device to drive a flow of gases into the inlet to thereby heat the exhaust gas treatment device.

Engine systems and methods use a dual air injection approach to control exhaust reactions and to maintain temperatures below a maximum limit of exhaust system components during engine enrichment operation conditions. Dual air injectors are disposed in the exhaust system with one upstream from, and another downstream from, the catalytic converter. Providing air injection before and/or after the converter helps convert all HC, CO, and PM emissions while keeping the catalyst temperature below the catalyst protection temperature limit. Air injection quantity may be controlled and diagnosed by monitoring the temperatures before and after the catalytic converter. The catalytic converter may be a three-way catalytic converter for lower cost or a downstream two-way catalytic converter may be added if further emission reduction is necessary.

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.

An engine assembly and a method of control thereof is provided. The engine assembly comprises: an exhaust gas aftertreatment device having an inlet for receiving exhaust gases leaving an engine; a heater for selectively heating gases at or upstream of the exhaust gas aftertreatment device; an air moving device for driving a flow of gases into the inlet of the exhaust gas aftertreatment device when the engine is in a non-running condition; and a controller configured to, prior to the engine being started: operate the heater to heat gases at or upstream of the inlet; and operate the air moving device to drive a flow of gases into the inlet to thereby heat the exhaust gas treatment device.

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.

A recycling loop configuration of an exhaust gas aftertreatment system decreases a level of system-out NO.sub.x emissions of an engine. An apparatus including the configuration has an exhaust gas recycling system having a closed gas recycling loop system configured to heat gas circulating within the loop, and a blower for circulating gas within the loop. A method for operating the engine includes preheating at least one aftertreatment component of an exhaust gas aftertreatment system of the engine by exposing the component to heated gas circulating in a closed gas recycling loop.

A valve device for an internal combustion engine. The valve device includes an actuator which moves a valve rod, a housing with an inlet and an outlet, a valve closing member attached to the valve rod which is lowered onto and lifted off of a first valve seat, a non-return plate which is loaded via a spring force in a direction of a second valve seat, and a sealing lip which is formed on the second valve seat or on the non-return plate. The sealing lip extends from the second valve seat in a direction of the non-return plate or from the non-return plate in a direction of the second valve seat. The sealing lip is formed with a free end which is inclined in a direction of a side on which a higher pressure is applied when the non-return plate rests on the second valve seat.

A recycling loop configuration of an exhaust gas aftertreatment system decreases a level of system-out NO.sub.x emissions of an engine. An apparatus including the configuration has an exhaust gas recycling system having a closed gas recycling loop system configured to heat gas circulating within the loop, and a blower for circulating gas within the loop. A method for operating the engine includes preheating at least one aftertreatment component of an exhaust gas aftertreatment system of the engine by exposing the component to heated gas circulating in a closed gas recycling loop.