What is a PCV valve for automobiles
The PCV valve (Crankcase forced ventilation valve) is a key component of an automotive engine. Its main function is to guide the mixture in the crankcase into the intake manifold for re-combustion, preventing direct gas leakage into the atmosphere and causing pollution. At the same time, it also prevents the deterioration of engine oil and engine wear.
Structure and working principle
The PCV valve is composed of a valve body, a valve, a valve cover and a spring, and its opening and closing degree is regulated by the vacuum degree of the intake manifold. When the engine is running at low speed or idling, the valve body is slightly open to introduce a small amount of the mixture. Fully open at high speed or during acceleration to increase the ventilation volume. When the engine backfires, the valve body automatically closes to prevent the crankcase from exploding.
Main functions
Youdaoplaceholder0 environmental protection : Prevent unburned mixed gas from being directly discharged into the atmosphere to avoid pollution.
Youdaoplaceholder0 Protect engine oil : Prevent gas leakage from diluting the oil and causing deterioration, thereby extending the engine's lifespan.
Youdaoplaceholder0 Control pressure : Balance the crankcase pressure to prevent lubricating oil leakage.
If the PCV valve is clogged, it may lead to contamination of the intake filter element, increased fuel consumption, accelerated engine wear or even damage. It is necessary to regularly clean the contaminants around it (such as checking the flexibility of the valve body and vacuum suction during regular maintenance).
PCV is the abbreviation of the three words "Positive Crankcase Ventilation" in English. In Chinese, it means the crankcase (or oil pan) active ventilation risk control system. The PCV valve is composed of a valve body, a valve, a valve cover and a spring, and cannot be disassembled. Its main function is: to introduce the gas in the crankcase into the intake manifold through the PCV valve, and a small amount of air directly enters the intake manifold from the air filter through the PCV valve. This avoids phenomena such as ice formation at the throttle, incomplete combustion, and deterioration of emissions. Prevent gas from entering the atmosphere and at the same time prevent the engine oil from deteriorating.
At the end of the engine's power combustion process, some unburned mixture leaks into the crankcase from the piston rings under high pressure. This kind of leakage is called "blow-by" in the industry. These blow-by gases will escape from the crankcase into the atmosphere, causing pollution. If these intruded mixtures are not expelled, they will also dilute the engine oil in the crankcase, causing the oil to deteriorate and leading to premature wear of engine components. Since the 1960s, California in the United States has been the first to require that cars be equipped with PCV systems, which have become a mandatory feature of automobiles.
Most gasoline engines are equipped with PCV valves (crankcase forced ventilation devices) to facilitate air exchange in the engine. However, contaminants in the bays can accumulate around the PCV valves, potentially causing them to clog. If the PCV valve is clogged, the contaminated gas will flow back into the air filter, contaminating the filter element, reducing the filtration capacity, resulting in increased fuel consumption, greater engine wear, and even engine damage. Therefore, it is necessary to maintain the PCV regularly and remove contaminants around the PCV valve.
The PCV valve is a metering control valve. It is installed between the crankcase ventilation system and the intake system of the engine. The PCV valve is controlled by the vacuum degree to regulate the flow of fumes generated by the crankcase ventilation system entering the intake system. When the engine is running at high speed, the flow should be higher than when it is running at low speed. At the same time, when the engine experiences backfire, the PCV valve should be able to cut off the ventilation to prevent the crankcase from exploding.
Every car has an exhaust pipe to expel the combustion exhaust gas from the engine to the outside of the vehicle. However, it is impossible to completely remove all the exhaust gas. A small amount of combustion exhaust gas will still enter the oil pan through the gap between the piston and the cylinder wall. Once the oil and gas entering the oil pan accumulate and cannot be discharged, it will form air pressure, which not only dilutes the engine oil but also causes poor lubrication of the engine parts. It will also cause serious consequences such as abnormal consumption of engine oil. Therefore, the oil and gas in the oil pan must have a discharge pipe. In the past, before the legislation and control of vehicle exhaust pollution, a pipe was connected to the oil pan to directly discharge the oil and gas into the atmosphere. The older the car gets, the more severe the leakage of combustion oil and gas becomes, and the more exhaust gas is discharged from the oil pan, causing serious air pollution.
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