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Why does the Engine Need Forced Crankshaft Ventilation?

One of the most important systems on a typical internal combustion engine is the forced crankshaft ventilation system, generally known as the PCV system. The high-pressure combustible mixture and the burned gas in the combustion chamber will more or less enter the crankshaft through the gap between the piston ring and the cylinder when the engine is running because the piston ring is not entirely sealed. blow-by effect unburned fuel gas, water vapor, and exhaust gas are the main components of blow-by gas. If the gas builds up too much over time, it will cause several failures.

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First, the oil is diluted, which decreases its performance and speeds up its oxidation and degradation.

Second, water vapor from the blow-by gas component condenses in the oil, creating sludge and clogging the oil circuit.

Third, the acid gas in the blow-by gas will combine with the lubrication system, causing corrosion and premature engine wear.

Fourth, the blow-by gas will raise the crankshaft pressure, damaging the seal and causing oil leakage and loss.

Fifth, allowing the exhaust gas to escape will pollute the environment and cause air pollution.

Crankshaft Ventilation

crankshaft ventilation is required to minimize excessive crankshaft pressure, extend the service life of the oil, reduce wear and corrosion of parts, and prevent engine oil from leaking. crankshaft ventilation system design must also be addressed in the car engine design process to fulfill increasingly strict pollution criteria and enhance the economy. This is the rationale for forced crankshaft ventilation in automobile engines.

Fault phenomenon after the crankshaft ventilation system is damaged:

Burning oil: This error is most noticeable when the engine’s oil consumption exceeds the recommended range, blue smoke is released during cold starts, and the engine fault light illuminates as an early warning, which may be accompanied by power loss, shaking, and other issues. This is because the wastegate valve’s oil and gas separation device malfunctions, allowing waste gas-containing oil to re-enter the combustion process and burn, resulting in the phenomena of burning oil. The wastegate valve needs to be replaced.

Oil leaking: The defect is most commonly represented as oil leakage from the crankshaft’s front and rear oil seals, oil leakage from the oil pan, and so on. The failure of the PCV valve or a blockage of the crankshaft ventilation line causes the crankshaft pressure to rise, causing oil leaks. The damaged oil seal and PCV valve need to be replaced.

Howling sound: When the engine is running, this issue causes a whistling sound comparable to boiling water, but it goes away when the oil cap is opened or the oil dipstick is removed. The vacuum diaphragm inside the exhaust valve has been broken, resulting in a whistling sound created by excessive negative pressure inside the engine. The exhaust valve needs to be replaced.

In addition to the forced ventilation system of the crankshaft, there is an issue that has been raised by the majority of riders: should I open the oil cap to inhale when the bike is idling? Or is it blowing?

Crankshaft Ventilation

In general, opening the oil cap with slight suction at idle speed is not a problem, but the negative pressure value established by the engine will vary depending on the tuning of different engines, such as self-priming and turbo. It is, nonetheless, excessive, whether inhaling or exhaling.

If a lot of air pressure comes out with the oil after you release the oil cap, it could suggest the piston ring isn’t well-sealed or the cylinder wall is significantly worn, allowing a lot of mixtures to escape into the crankshaft and then into the valve chamber via the oil route. Of course, the exhaust valve breathing tube is also blocked, causing the internal pressure to rise and the exhaust gas to circulate.

If there is a lot of suction when opening the oil cap, that is, the oil cap is difficult to pick up, it could suggest that the wastegate valve is normally open, the intake manifold’s suction impact is obvious, and the negative pressure in the engine increases, resulting in increased suction power. The specific suction size is normal. You can use a vacuum gauge to measure the standard range of negative pressure in your car’s engine after first understanding it. This is the most natural approach to detecting and judging quantitative data.

Well, the above is part of the crankshaft ventilation system; I hope it is useful to all riders and reduces the problems associated with regular automobile use and maintenance!


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