Crankcase ventilation, also known as the positive crankcase ventilation (PCV) system, is designed to remove harmful gases and excess pressure from the crankcase of an internal combustion engine. This system is present in many motorcycles, just like in cars and other vehicles.
The crankcase is the lower part of the engine where the crankshaft is located. During the combustion process, some gases known as blow-by gases can escape past the piston rings and enter the crankcase. These blow-by gases contain unburned fuel, water vapor, and combustion byproducts, and if left uncontrolled, they can cause various issues such as increased engine pressure, oil contamination, and increased emissions.
The crankcase ventilation system consists of several components. Here's a simplified explanation of how it typically works on a motorcycle:
Positive Crankcase Ventilation Valve (PCV Valve): The PCV valve is a one-way valve located in the engine's crankcase. It allows gases to flow out of the crankcase but prevents them from flowing back in. The valve opens when there is negative pressure in the intake manifold.
Crankcase Ventilation Hose: Connected to the PCV valve, the crankcase ventilation hose provides a pathway for the blow-by gases to exit the crankcase. It typically directs the gases back into the intake manifold or the air intake system.
Intake Manifold: The intake manifold supplies air-fuel mixture to the engine's combustion chambers. In a motorcycle, the crankcase ventilation hose often connects to the intake manifold, allowing the blow-by gases to be drawn into the combustion chambers for re-burning.
Combustion Chambers: The blow-by gases, along with the fresh air-fuel mixture, enter the combustion chambers where they undergo combustion as part of the normal engine operation. This helps eliminate the harmful gases by burning them off.
Emissions Control: The PCV system also plays a role in reducing harmful emissions. By recirculating the blow-by gases back into the combustion chambers, they can be effectively burned, reducing the release of pollutants into the atmosphere.
Overall, the crankcase ventilation system ensures that the blow-by gases are properly controlled, preventing issues such as pressure buildup, oil contamination, and excessive emissions. By allowing the gases to be burned off in the combustion chambers, it helps maintain the engine's efficiency and reduces environmental impact.