* Engine size and design: Larger engines generally have higher crankcase pressures and therefore higher PCV flow rates. Engine design (e.g., piston rings, blow-by) also significantly impacts this.
* Engine condition: Worn piston rings or valve guides will lead to increased blow-by and thus higher PCV flow.
* Oil viscosity: Thicker oil can slightly restrict PCV flow.
* PCV valve condition: A clogged or malfunctioning PCV valve will drastically reduce or completely block airflow.
* Ambient conditions: Temperature and atmospheric pressure can subtly affect crankcase pressure.
While you won't find a precise figure in a specification sheet, it's generally a relatively small amount of air, measured in cubic centimeters per minute (ccm) or liters per minute (lpm) at idle. It's often much less than 1 liter per minute. The flow significantly increases at higher engine speeds.
Trying to measure this accurately requires specialized equipment and procedures. Instead of focusing on the exact flow rate, it's more practical to assess the system's functionality by checking for proper PCV valve operation and observing for excessive crankcase pressure (which can be an indicator of a problem).
