Abstract: A blowby gas treatment device includes a pressure control valve, a fresh air induction pipe, a first blowby gas pipe, a second blowby gas pipe, a shutoff valve, a one-way valve, and a PCV valve. A leak diagnosis includes a first-stage diagnosis to determine whether or not falling of a pressure in a crank case after closing of the shutoff valve under a non-supercharging condition is normal. A second-stage diagnosis is implemented by using an air fuel ratio feedback control, and determining whether or not a sensed intake air quantity obtained by an air flow meter is equal to an actual intake air quantity flowing into a cylinder set. When the sensed intake air quantity is equal to the actual intake air quantity, presence of an in-system leak is determined, and when the actual intake air quantity is larger, presence of an out-of-system leak is determined.

Abstract: An oil structure of an internal combustion engine includes a main oil pump configured to suck lubricating oil stored in a crankcase and feed the lubricating oil to respective engine parts and a scavenge pump configured to recover the lubricating oil from any lubricated engine part and return the lubricating oil into the crankcase. The scavenge pump has: an oil suction passage extending from the lubricated engine part to a suction side of the scavenge pump; and an air introduction passage for negative pressure control connected to the oil suction passage. An air introduction port of the air introduction passage is open to the inside of the crankcase and is set to a height position such that, when a level of the lubricating oil in the crankcase is inclined, the lubricating oil flows in from the air introduction port and returns from the scavenge pump into the crankcase.

Abstract: A blowby gas treatment device includes a pressure control valve, a fresh air induction pipe, a first blowby gas pipe, a second blowby gas pipe, a shutoff valve, a one-way valve, and a PCV valve. A leak diagnosis includes a first-stage diagnosis to determine whether or not falling of a pressure in a crank case after closing of the shutoff valve under a non-supercharging condition is normal. A second-stage diagnosis is implemented by moving the pressure control valve from a fully opened state into a fully closed state, and determining whether an intake air quantity in each state is equal to each other. When the intake air quantity in each state is equal to each other, presence of an in-system leak is determined. When a fully closed state intake air quantity is different from a fully opened state intake air quantity, presence of an out-of-system leak is determined.

Abstract: A blowby gas treatment device includes a pressure control valve, a fresh air induction pipe, a first blowby gas pipe, a second blowby gas pipe, a shutoff valve, a one-way valve, and a PCV valve. A leak diagnosis includes a first-stage diagnosis to determine whether or not falling of a pressure in a crank case after closing of the shutoff valve under a non-supercharging condition is normal. A second-stage diagnosis is implemented by moving the pressure control valve from a fully opened state into a fully closed state, and determining whether an intake air quantity in each state is equal to each other. When the intake air quantity in each state is equal to each other, presence of an in-system leak is determined. When a fully closed state intake air quantity is different from a fully opened state intake air quantity, presence of an out-of-system leak is determined.

Abstract: A blowby gas treatment device includes a pressure control valve, a fresh air induction pipe, a first blowby gas pipe, a second blowby gas pipe, a shutoff valve, a one-way valve, and a PCV valve. A leak diagnosis includes a first-stage diagnosis to determine whether or not falling of a pressure in a crank case after closing of the shutoff valve under a non-supercharging condition is normal. A second-stage diagnosis is implemented by using an air fuel ratio feedback control, and determining whether or not a sensed intake air quantity obtained by an air flow meter is equal to an actual intake air quantity flowing into a cylinder set. When the sensed intake air quantity is equal to the actual intake air quantity, presence of an in-system leak is determined, and when the actual intake air quantity is larger, presence of an out-of-system leak is determined.