A sliding cam system for an internal combustion engine is disclosed. The sliding cam system includes a carrier shaft and an axially adjustable cam sleeve arranged on the carrier shaft. The cam sleeve is axially adjustable relative to the carrier shaft between a first axial position and a second axial position, and axially fixable in the respective axial position by a detent device. The detent device includes a first receiving groove assigned to the first axial position and a second receiving groove assigned to the second axial position. The detent device further includes a preload element disposed on the cam sleeve. The preload element preloads a detent element arranged between the carrier shaft and the cam sleeve towards the carrier shaft. The detent element is received in the first receiving groove in the first axial position and the second receiving groove in the second axial position.

A shift gate for a sliding cam system may include at least two shift grooves for engagement of at least one actuator pin. The two shift grooves run against a direction of rotation and transform from a first inlet portion for the actuator pin into a second outlet portion for the actuator pin. The two shift grooves cross one another in an intersection region between the two portions. In the intersection region, the two shift grooves each have a maximum axial shift stroke that is greater than half a total axial shift stroke, in particular a slide travel, of the shift gate.

Systems and methods for operating an engine with deactivating and non-deactivating valves are presented. In one example, valves of a cylinder are deactivated in a closed state in response to an indication of degradation of a valve of the cylinder. Further, fuel flow to the cylinder may be stopped via ceasing to inject fuel to the cylinder.

A valve actuation system includes a rocker for conveying motion to an engine valve, a motion source arranged to impart motion to the rocker, rocker stop assembly configured to operate in an activated mode, in which the rocker stop assembly maintains the rocker in a position corresponding to partial valve lift, and a deactivated mode, in which the rocker stop assembly allows the rocker to move to a position corresponding to a fully closed valve position, and a rocker stop reset assembly for resetting the rocker stop assembly to the deactivated mode subsequent to a main event peak lift to thereby achieve late valve closing. A damper assembly may interact with the rocker stop assembly to provide a smooth transition of the rocker and valve motion to a late intake valve closing dwell. A valve catch assembly may control the seating velocity of the at least one valve.

Methods and systems are provided for cylinder deactivation to reduce tailpipe emissions and increase exhaust temperature. In one example, a method may include operating a first set of cylinders in a first combustion cycle over modified eight strokes and a second set of cylinders in a second combustion cycle over modified four strokes. Each cylinder in the first set of cylinders may be selectively deactivated via a variable displacement engine (VDE) mechanism while each cylinder in the second set of cylinders may be selectively deactivated via an active decompression technology (ADT) mechanism.

A valvetrain for an internal combustion engine includes a camshaft, an electromagnetic latch assembly, a rocker shaft, and a rocker arm assembly. The rocker arm assembly may include a cam follower configured to engage a cam mounted on the camshaft as the camshaft rotates and a rocker arm configured to rotate on the rocker shaft. The electromagnetic latch assembly may include a pin translatable between a first position and a second position and an electromagnet that causes the pin to actuate. The movement of the pin may provide mode switching for a switching rocker arm, a cylinder deactivating rocker arm, or an engine brake rocker arm. The electromagnet is powered by a circuit that passes through the rocker shaft. The electromagnet may be mounted to the rocker shaft. Running the circuit through the rocker shaft allows the electromagnet to be powered with wiring that remains stationary.

A lift-valve assembly, comprising a lift valve within a housing that includes a pressure segment, a mounting segment, a port segment, and a seat segment. The lift-valve assembly may receive a lift valve, and the housing including a valve seat and a biasing spring in a selectively replaceable configuration suitable for use in a conventional internal combustion engine in place of the conventional individual components, actuated by a cam actuating system, and controlling fluid communication between a combustion chamber and both intake and exhaust systems.

Hydraulic systems in an engine valvetrain having lost motion and/or braking hydraulic circuits are provided with a conditioning circuit that may include a supplemental supply passage, which provides continuous and supplemental supply of hydraulic fluid from a supply source to the braking and lost motion circuits, as well as a venting of the circuits to ambient, such that the hydraulic fluid in these circuits is kept in a refreshed and conditioned state without air contamination. A vented three-way solenoid valve may be utilized. The supplemental supply passage may be provided at various locations in the valvetrain and in the engine head environment. The supplemental supply passage may include flow and pressure control devices to control the flow of the supplemental supply of hydraulic fluid.

An engine is provided, which includes an engine body including a plurality of cylinders, each of the cylinders being provided with an intake port, an exhaust port, an intake valve, and an exhaust valve, an intake passage and an exhaust passage connected to the engine body, and a turbocharger including a turbine provided to the exhaust passage and a compressor provided to the intake passage. A geometric compression ratio of the cylinder is 11:1 or higher. An open period of the intake valve is a range of 270° or larger by a crank angle. The exhaust passage includes a plurality of independent exhaust passages, each communicating with the exhaust port of one cylinder or with the exhaust ports of two or more cylinders of which timings of exhaust strokes are discontinuous from each other, and connecting the engine body to the turbine.

Methods and systems are provided for providing secondary air to an exhaust system during catalyst warm-up. In one example, a method may include, during a cold start condition, operating an engine with a first number of cylinders unfired and a remaining number of cylinders fired during an engine cycle, opening an intake valve of an unfired cylinder of the first number of cylinders during an expansion stroke of the unfired cylinder, and opening an exhaust valve of the unfired cylinder during a compression stroke of the unfired cylinder. In this way, the unfired cylinders may provide the secondary air to the exhaust system during a stroke that increases mixing of the secondary air with burned exhaust gas from fired cylinders, thus increasing exotherm production in the exhaust system to increase a temperature of the catalyst.