An internal combustion engine having an engine block, a cylinder head, a crankcase and at least one cylinder includes a crankcase ventilation line connected to at least one intake line. The crankcase ventilation line is arranged at least predominantly within the internal combustion engine, in particular within the engine block and/or within the cylinder head, thereby greatly minimizing or eliminating the potential for release of crankcase gas to the environment.

Methods and systems are provided for indicating crankcase breach due to disconnection of a crankcase vent tube from an engine on a clean air side or broken crankcase vent tube. In one example, a maximum possible change in crankcase vent tube pressure is estimated for each pedal transient of a drive cycle. The change for a plurality of transients in averaged and compared to a threshold to identify vent tube disconnection.

In an engine head cover, an upper portion of a partition plate 5, which partitions an inside of a head cover 3 into upper and lower portions, forms a blowby gas passage W having an inlet 6 and an outlet 7 communicating with an intake path 9. A PCV valve 14 disposed on the outlet 7 side, a filter 13 disposed on the inlet 6 side, and a labyrinth 15 disposed between the PCV valve 14 and the filter 13 are provided. A recovery hole 23 which causes a flowdown of trapped oil is formed at a portion on a downstream side of the filter 13 in a flow direction of a blowby gas in the blowby gas passage W and on a lower side of the labyrinth 15 and the pressure regulating valve 14.

Methods and systems are provided for diagnosing a positive crankcase ventilation (PCV) system. In one example, a diagnostic method for a PCV system is provided that includes, when an intake manifold air pressure is above a threshold boost value, determining a PCV system breach based on a pressure determined using a pressure sensor positioned on a clean side of an oil separator coupled to a crankcase and receiving crankcase gas from the crankcase. In the PCV system a ventilation line provides fluidic communication between the oil separator and an intake conduit upstream of a compressor.

In a method for avoiding a runaway condition of an internal combustion engine that includes a cylinder, an operational characteristic of the engine, presumed to be caused by an unrequested introduction of hydrocarbon into the cylinder, is detected and the engine is derated in dependence of the detection, and, while the engine is derated, a test procedure is performed to detect an unrequested introduction of hydrocarbon into the cylinder.

Methods and systems are provided for indicating crankcase breach due to disconnection of a crankcase vent tube from an engine on a clean air side or broken crankcase vent tube. In one example, a maximum possible change in crankcase vent tube pressure is estimated for each pedal transient of a drive cycle. The change for a plurality of transients in averaged and compared to a threshold to identify vent tube disconnection.

An abnormality determination device of an internal combustion engine in which a breather line connects an intake-air path positioned upstream from a forced-induction system and a crankcase includes an intake-air flow rate sensor that detects an intake air flow rate in the intake-air path, a pressure sensor that detects a pressure of the breather line, and an abnormality determination unit that determines abnormality of the breather line. The abnormality determination unit estimates an intake air resistance of the intake-air path from the pressure when the engine is under low load conditions under which the intake air flow rate is less than a predetermined value and the pressure when the engine is under high load conditions under which the intake air flow rate is the predetermined value or greater and determines abnormality of the breather line when the intake air resistance is less than a threshold.

An abnormality assessment device includes an on-off valve that shuts an intake path on an upstream side of a connection portion of a breather line with respect to the intake path and an abnormality assessment element that assesses abnormality of the breather line. The abnormality assessment element assesses abnormality of the breather line based on a difference between an intake flow rate that is detected by an intake flow rate sensor and a target intake flow rate in a case where the on-off valve is closed.

An abnormality determination device of an internal combustion engine in which a breather line connects an intake-air path positioned upstream from a forced-induction system and a crankcase includes an intake-air flow rate sensor that detects an intake air flow rate in the intake-air path, a pressure sensor that detects a pressure in the breather line, and an abnormality determination unit that determines abnormality of the breather line. The abnormality determination unit compares the pressure and a threshold for each flow rate, integrates a number of times the pressure becomes the threshold or greater, and determines abnormality of the breather line when an integrated value becomes a predetermined value or greater within a predetermined time. The abnormality determination unit calculates a weight coefficient for each flow rate and assigns weights to a number of times the pressure becomes the threshold or greater by using the weight coefficient.

A method for ventilating a crankcase of an internal combustion engine using natural gas as a fuel source may include filtering ambient air through an air filter. The method may also include heating the filtered ambient air by a jacket heat exchanger. The method may further include directing the heated ambient air through an inlet of the crankcase to purge blow-by gases including natural gas from the crankcase.