What are the types of crankcase ventilation?
2 Answers
Crankcase ventilation includes natural ventilation and forced ventilation. Natural ventilation: Natural ventilation involves installing a ventilation pipe on the crankcase, equipped with an air filter screen. Forced ventilation: Forced ventilation directs the mixed gas in the crankcase to an appropriate position in the intake pipe through a connecting pipe, allowing it to return to the cylinder for re-combustion. This not only reduces exhaust pollution but also improves the engine's fuel efficiency. Gasoline engines for vehicles generally adopt forced ventilation, and diesel engines for vehicles are gradually adopting it as well. Forced ventilation can be divided into open and closed types. In open forced crankcase ventilation systems, when the engine operates at full load and low speed, the amount of blow-by gas generated is large, but the opening of the flow control valve decreases. Excessive blow-by gas will escape into the atmosphere through the open ventilation cover, with a purification rate of only about 75%. Closed forced crankcase ventilation systems can fully control crankcase emissions, achieving a clean crankcase.
There are two main types of crankcase ventilation: open and closed. The open type simply vents the gases directly into the atmosphere—simple and straightforward, but it pollutes the environment and often spreads oil residue everywhere. As a mechanic, I frequently see issues with older cars using this method. The closed type, on the other hand, uses pipes and a PCV valve to redirect the gases back into the intake system for re-combustion, reducing emissions and being more environmentally friendly. Modern cars are mostly designed this way. Poor ventilation can lead to increased crankcase pressure, causing oil leaks or even oil burning, which affects engine lifespan. During maintenance, it's crucial to check that the PCV valve isn't clogged and to clean or replace it periodically to prevent carbon buildup from affecting performance.
