And if they don't, I would assume it is better to get one with a filter?

 

A catch can just catches the excess blow-by. . . . why would it need a filter? It is just catching misc. oil from whatever source you plug the line into, which you then dump at a point after driving, no? Of course, if I am wrong, please do correct me.

 

What you are saying makes sence but i have seen some with and some without. I just wanna know why, and what difference it makes.(if any)

Thanx for the reply

 

When you say blow by I would guess the excess would be put in the can by some amount of pressure. If there's no breather/or filter on the can it will just pressurize the container and it's hard to put excess fluid in a presurrized container, so I would think a filter or breather would be necessarry. ? ? ? ? ? ?

 

That makes alot of sense. Hence the method of connecting it to the intake side of the turbo for even better evacuation.