In an internal combustion engine, blow-by gases in the crankcase are evacuated and reburned via the Positive Crankcase Ventilation (PCV) system. What is the correct chronological order of the stages in the PCV operational cycle, from the initial formation of crankcase vapors to their final elimination?
- 1High-pressure combustion gases and unburned fuel leak past the piston rings into the engine crankcase.
- 2Fresh air drawn through a breather filter mixes with the accumulated crankcase fumes.
- 3Intake manifold vacuum draws the vapor mixture through the spring-loaded PCV valve.
- 4The metered vapors are discharged directly into the intake manifold plenum.
- 5The vapor mixture blends with incoming air-fuel charge and burns in the combustion chambers.
Answer
The correct sequence starts with blow-by gases leaking past the piston rings, mixing with fresh breather air in the crankcase, passing through the PCV valve under intake vacuum, entering the intake manifold plenum, and finally burning in the combustion chambers.
The Positive Crankcase Ventilation cycle operates in a closed loop driven by manifold vacuum. First, combustion blow-by slips past the piston rings into the crankcase. Second, fresh air enters through the breather filter to sweep and dilute these vapors. Third, intake vacuum pulls the mixture through the spring-loaded PCV valve. Fourth, the metered vapors enter the intake manifold plenum. Finally, the gases are drawn into the cylinders to be safely incinerated during the combustion stroke.
Step-by-Step Solution
Key Concept
The Positive Crankcase Ventilation (PCV) system utilizes intake manifold vacuum to draw blow-by gases out of the crankcase through a metering valve and into the intake manifold so they can be reburned in the combustion chambers.
Estimated Time:1m 15s