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.

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.

A leakage detection device detects leakage in a PCV passage that at least includes a scavenging line that communicates between a crank chamber of an engine and a portion of an intake passage of the engine that is on a downstream side of a throttle valve and a fresh air line that communicates between the crank chamber and a portion of the intake passage that is on an upstream side of the throttle valve. The leakage detection device includes a pressure measurement, a first valve and a leakage determination unit. The pressure measurement unit measures pressure in the PCV passage. The first valve opens/closes the fresh air line. The leakage determination unit determines presence or absence of leakage in the PCV passage on a basis of the pressure in the PCV passage at a time when the first valve is closed.

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 internal combustion engine includes on-off valves that configure a closed space by closing an internal space of a breather line, a pump that depressurizes or pressurizes the closed space, a pressure sensor that detects a pressure of the closed space, 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 pressure change of the closed space in a case where the closed space is depressurized or pressurized by the pump.

An abnormality determination apparatus for an internal combustion engine in which an intake passage upstream of a supercharger and a crankcase are connected by a breather line includes: an intake flow rate detection unit that detects an intake flow rate in the intake passage; and an abnormality determination unit that determines abnormality of the breather line. The abnormality determination unit accumulates a time for which a rotation second-order component of a fluctuation waveform of the intake flow rate is equal to or more than a threshold over a predetermined period of time and determines the abnormality of the breather line when the accumulated value is less than a predetermined accumulation threshold.

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.

An internal combustion engine includes: a cylinder block including a bulkhead formed so as to separate adjacent cylinders; a crankshaft including a counterweight; and a gas-vent hole which is formed in the bulkhead within a radius of rotation of the counterweight when seen from below a piston bottom-dead-center position and an axial direction of the crankshaft, and which communicates between the adjacent cylinders. The counterweight includes at least one of a concave portion and a through-hole formed at at least a part of a region of the counterweight opposed to the gas-vent hole during rotation of the crankshaft. The concave portion hollows in a direction away from the gas-vent hole, the through-hole penetrating through the counterweight in a direction away from the gas-vent hole.