PCV Valve equivalant?

[FWBennett]

Please bear with me cuz I'm learning - OK I know that the CDR (Crankcase Depression Regulator) Valve sucks the fumes/smoke from the crank case - is there a PCV (Positive Crank Case Valve)equivalant that lets fresh air into the crank case? or is the crankcase under constant vacuum?

[britannic]

There isn't a PCV that admits fresh air, only the blowby from the piston rings. The CDR maintains negative crankcase pressure to prevent the seals from leaking and purge oil vapor and the tiny amount of exhaust gas that blows by the rings.

[Dieselfume]

CDR's are made to handle higher volume than most any PCV because of the lack of vacuum on a diesel. I doubt any PCV would work as good as a properly functioning CDR valve.