so i recently installed a j's racing catch can, currently i have the lines routed like so:
pcv->catch can->intake manifold.


weird thing is, when i rev the car, i can hear a whoosing sound from the catch can. almost sounds like theres a leak in the catch can. however, i then tried plugging the intake manifold and just letting the catch can vent into the atmosphere like so:


and voila! the sound was gone. any idea why?! can't be a leak, otherwise i would still hear the sound using the second configuration. also, when i rev the car, i can kind of feel the metal on the catch can...expand for a lack of better words.

 

i would assume the "wooshing" sound might be due to the vacuum from intake manifold being worked on the catch can, or maybe because of the oil collected in the catch can making a "wooshing" sound from manifold vacuum?

metal on catch can expanding? well i assume this is due to the fact that the fumes coming out from the block is high in temperature, and as you know metal expands when heated.

jus sharin my thoughts.

o and is the catch can vented or non vented? maybe the area where u can put a filter on (for vented catch cans) might not have a complete seal. this could explain why you get wooshing sound only when catch can is connected to intake manifold.

 

i was thinking the noise is a result of the vacuum from the intake manifold pulling air from the crankcase, but i dont understand why my previous catch can didnt make this noise

catch can is non vented

 

maybe its the air wooshing thru what used to be just a rubber tube. turbulent flow inside the catch can?