What is the normal crankshaft case pressure?

[JaxsonFitz]

The normal negative pressure value for the crankshaft case is -350mbar. The engine's crankshaft ventilation system is a forced ventilation system, where the crankshaft case is connected to the intake pipe. The vacuum from the intake system draws the gases from the crankshaft case into the cylinders. As a result, the crankshaft case maintains a negative pressure state under most operating conditions, with the magnitude of the negative pressure related to the intake system pressure. To prevent excessive crankshaft case pressure, extend the service life of the engine oil, reduce component wear and corrosion, and prevent engine oil leaks, crankshaft case ventilation must be implemented. The purposes of crankshaft case ventilation are as follows: Prevent lubricating oil deterioration and fuel dilution of the oil, reducing wear and corrosion of engine components. Pressure reduction, temperature reduction, and leak prevention: Gases leaking into the crankshaft case increase the pressure and temperature inside, causing oil to leak through the crankshaft seals and gaskets. Recover combustible gases and reduce pollution. The gases that enter the crankshaft case are drawn back into the cylinders for combustion, recycling CH compounds and reducing atmospheric pollution.