Quote:
Originally Posted by mrg666
Because WRX valve is designed for boosted engine and can hold higher pressure inside intake manifold from leaking into crankcase while stock valve starts to leak that boost into crankcase. But crankcase starts ventilating more oil with the air that goes into intake manifold with a boosted engine. When the oil catch can is added to avoid that oil going to intake manifold, it is also better to avoid the boost pressure expanding into catch can before being stopped on the PCV side. That is why adding a check valve between the catch can and intake manifold is better than replacing the PCV valve with WRX valve. Since boost is blocked at the exit of intake manifold, check valve reacts quicker. Hope I didn't make this too complicated 
Edit: Another benefit is that the oil clogs up the PCV valve mechanism after a while. However, the check valve will experience less oil on the other side of oil catch can. |
Is it ok to do both or is it overkill? I mean the items are like $20 a piece, so cost isn’t a factor. Would one completely negate the other or could it be worse to do both than just one? Thanks.