What is the working principle of the automotive PVC valve?
2 Answers
PCV valve working principle: The PCV valve is a metering control valve. It is installed between the engine crankcase ventilation system and the intake system. The PCV valve is controlled by vacuum to regulate the flow of oil fumes generated by the crankcase ventilation system into the intake system. The flow rate is higher when the engine is running at high speed compared to low speed. Additionally, when engine backfire occurs, the PCV valve should cut off ventilation to prevent crankcase explosion. Here is additional information: Related knowledge: PCV is the abbreviation of the English words Positive-Crankcase-Ventilation, meaning the positive ventilation control system of the crankcase (or oil pan). The PCV valve consists of a valve body, valve, valve cover, and spring, and is non-disassemblable.
The full name of the automotive PCV valve is the Positive Crankcase Ventilation valve, and its working principle is quite interesting. Simply put, when the engine is running, piston movement allows some gases to leak into the crankcase, increasing the pressure. The PCV valve acts like a small regulator, using the vacuum suction generated by the intake manifold to draw these exhaust gases back into the engine for combustion. The valve features a spring design that automatically opens and closes in response to pressure changes: opening wider when vacuum is strong and closing slightly when it weakens. This not only prevents engine oil from degrading into sludge but also reduces pollutant emissions, which is crucial for engine longevity. I've seen many older vehicles experience oil leaks or poor acceleration due to a stuck valve, so it's essential to inspect it every two years, especially during seasons with significant temperature variations like winter and summer.
