Size a positive crankcase ventilation valve based on engine displacement, blowby rate, and crankcase pressure management.
Input Parameters
Results
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Blowby Flow Rate
cfm
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Required PCV Flow
cfm
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PCV Orifice Size
mm
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Target Crankcase Vacuum
inH2O
Note: PCV maintains slight crankcase vacuum (1-3 inH2O) to prevent oil leaks and contamination. Excessive blowby (>3%) indicates ring/bore wear.
Reference
Displacement CFM = Disp(ci) x RPM / (2 x 1728) x VE
Blowby Flow = Displacement CFM x Blowby%
PCV Flow = Blowby x 1.5 (safety factor)
Orifice Area = PCV Flow / (Cd x Velocity)
Orifice Dia = sqrt(4 x Area / pi)