Hello everyone,

I did some searching and couldn't really find much info. I'd like to get some input on the idea of running a catch can with, and without, a breather.

I am fashioning my own intake for my TSX, and as I pull vacuum lines off the factory intake pipe, I am naturally considering rigging up a catch can.

It seems my options are either one with a breather, like this:


Or one without


The idea of the catch can, as I see it, is to keep oil out of your intake, while your intake pulls some vacuum on your crankcase.

However, the one with the breather makes no sense to me. The vacuum draw on the catch can is simply going to suck in air through the filter, not pull any vacuum out of your crankcase. positive pressure will be able to vent out of the crank case, but whats the point of running the can? It seems like this setup would do the same thing:


The advantage of this I suppose is that you won't get any oil fumes and particles suspended in the air into your intake. But, in my mind, the advantage to running a sealed can and actually sucking air out of the engine is worth a little oil vapor in the intake.

...Or is the complete removal of all oil vapor and particles with the loss of vacuum on the crankcase?

 

a catch can serves only ONE purpose: to catch the oil that travels through the vent line[s] or the pcv line.

you use a catch can with a filter on it for the breather vent[s]. to connect this you run the breather hoses from the valve cover to the can, and the can has a filter on it so when air gets sucked in it doesn't let debris in, and when air gets blown out the can catches any oil in the air.

you use a sealed catch can with no breather/filter if you want to still use a valvecover mounted pcv valve without oil getting into the intake mani. for this you would run the pcv valve side hose to one port on the can, and the intake mani side pcv hose to the other port on the can. this way it's still a sealed system for the pcv, but any oil coming out of the pcv valve will get trapped in the can before making it to the intake mani.

 

catch can's do NOT create vacuum in the crankcase. they simply give you something to connect vent hoses to (or pcv hose), to catch the oil that flows through the vent hoses (or pcv hose). nothing more nothing less

 

My catch can is a combination of the two, although mine started as the sealed unit. Im running the PVC line to the can as you normally would. My cans openings are on opposite sides so i can put the mini filter on the one the would go to the intake mani without being in the way.

I dont want a sealed unit, I dont want anything dirtying up my air. I removed all of my emissions, and would still like to pass my states smog. With a emissions tuned Map uploaded to my Neptune, a high flow cat, and no unnecessary dirty air, I hope to pass still.