A moment-cancelling, four-stroke engine is disclosed. The engine includes a first cylinder having a first piston and a second cylinder having a second piston, a first crankshaft operably connected to the first piston and a second crankshaft operably connected to the second piston. The first crankshaft rotates in a first direction and the second crankshaft rotates in a second direction that is opposite the first direction to cancel the moments applied to the engine and reduce engine vibration.

An intake cam is positioned between first and second shaft supports that support an intake camshaft. An exhaust cam is positioned between third and fourth shaft supports that support an exhaust camshaft. An ignition plug unit extends between the intake camshaft and the exhaust camshaft and inward of the intake cam and the exhaust cam with a cylinder axis defining a reference position. A cylinder head includes a joint plane that is joined to a cylinder body. In a case where a virtual plane is defined by the joint plane and is perpendicular or substantially perpendicular to the cylinder axis, a distance between a portion, closest to the virtual plane, of the intake camshaft and the virtual plane is less than a distance between a portion, farthest from the virtual plane, of the intake port and the virtual plane.

A mechanical system, comprising a support element, a pin extending along a first axis and comprising two opposite ends, each adapted to be fitted in the support element for radial retention of the pin relative to the first axis, and a roller element movable in rotation relative to the pin around the first axis. The mechanical system includes two ribs resting on either side of the ends for axial retention of the pin along the first axis. The mechanical system can be integrated into either an injection pump or a valve actuator.

A follower mechanism movable within a bore, the mechanism including an outer cup with a substantially cylindrical side wall and a first annular lip portion disposed at a first end of the side wall, an inner cup including a side wall portion defining a pair of shaft apertures and a ledge that is transverse to a longitudinal center axis of the follower mechanism, the inner cup being disposed in the outer cup so that the first annular lip portion of the outer cup abuts a top surface of the side wall portion of the inner cup, a pallet having an outer perimeter, at least a portion of the outer perimeter being adjacent the ledge of the inner cup, a shaft having a first end and a second end disposed in the shaft apertures, and a roller follower rotatably received on the shaft.

An internal combustion engine system includes an engine with a plurality of pistons housed in respective ones of a plurality of cylinders, an air intake system to provide air to the plurality of cylinders through respective ones of a plurality of intake valves, an exhaust system to release exhaust gas from the plurality of cylinders through respective one of a plurality of exhaust valves. A valve train is provided for cylinder deactivation of a first part of the plurality of cylinders and compression release braking on a second part of the plurality of cylinders.

A bi-fuel internal combustion engine system includes a first fuel system, a second fuel system, and a bi-fuel internal combustion engine. The bi-fuel internal combustion engine is configured to selectively consume one of a first fuel received from the first fuel system and a second fuel received from the second fuel system. The bi-fuel internal combustion engine includes a camshaft and a valve assembly. The camshaft has a cam. The valve assembly is positioned adjacent the camshaft and configured to interface with the cam. The valve assembly is selectively repositionable between a first position and a second position. The bi-fuel internal combustion engine has a first dynamic compression ratio when the valve assembly is in the first position and a second dynamic compression ratio when the valve assembly is in the second position. The second dynamic compression ratio is greater than the first dynamic compression ratio.

A system includes an engine with a plurality of pistons housed in respective ones of a plurality of cylinders, an air intake system provides air to the plurality of cylinders through respective ones of a plurality of intake valves, an exhaust system to release exhaust gas from the plurality of cylinders through one of a plurality of exhaust valves, and a controller coupled to a sensor to control a switching tappet for compression release braking. Alternatively to a tappet, the system includes a roller finger follower controlling an opening and closing timing of exhaust valves, the roller finger follower has an inner roller follower arm adjacent an outer sliding follower, and a controller that in response to an engine braking request locks the inner roller follower arm with the outer sliding follower to contact a second cam lobe and open the exhaust valve during a compression stroke of the cylinder.

A follower mechanism movable within a bore, the mechanism including an outer cup with a substantially cylindrical side wall and a first annular lip portion disposed at a first end of the side wall, an inner cup including a side wall portion defining a pair of shaft apertures and a ledge that is transverse to a longitudinal center axis of the follower mechanism, the inner cup being disposed in the outer cup so that the first annular lip portion of the outer cup abuts a top surface of the side wall portion of the inner cup, a pallet having an outer perimeter, at least a portion of the outer perimeter being adjacent the ledge of the inner cup, a shaft having a first end and a second end disposed in the shaft apertures, and a roller follower rotatably received on the shaft.

An internal combustion engine system includes an engine with a plurality of pistons housed in respective ones of a plurality of cylinders, an air intake system to provide air to the plurality of cylinders through respective ones of a plurality of intake valves, an exhaust system to release exhaust gas from the plurality of cylinders through respective one of a plurality of exhaust valves. A valve train is provided for cylinder deactivation of a first part of the plurality of cylinders and compression release braking on a second part of the plurality of cylinders.

Methods and systems are provided for controlling engine knock. In one example, a method may include decreasing intake valve lift at a first set of cylinders where knock is indicated and increasing intake valve lift at a second set of cylinders where knock is not indicated. A stoichiometric air-to-fuel ratio is thereby maintained.