Catch Can FAQ

[fleezy]

can i make a 4 port catch can instead of 2 2 ports?

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[Vancouver98STi]

Originally Posted by KCRS01

when you use a closed loop system the oil just recirculates in the system, meaning, if it has dirt/contaminants it just go back to the engine.

while vent to atmosphere AOS vents the oil going to the pipe and going to the street. the dirty oil in the system is then completely removed and not recirculated.

Ummm.... there appears to be some sort of confusion here. Venting (or not venting) the PCV system to the atmosphere has nothing to do with where collected oil goes. These are two separate variables. The catch cans I use do not drain back into the crankcase, and it's a closed system... as Subaru originally intended it to be.
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[VinceS2]

Because of the length of this thread, I started a new thread with a guide on what the smartest way to do the catch can mod is on a standard TMIC setup. See https://forums.nasioc.com/forums/sho....php?t=2879743
Just figured it was appropriate to cross-reference this thread back to that one, for completeness.

[edmartin81]

Thanks for the post. I've been debating whether to install one on my EJ. I knew catch cans were needed to keep the FA ports from gumming up, but I didn't consider oil vapor condensing in the intercooler.

[GK1707]

Anyone know the hose sizes? I'm reading 3/8 between and 1/2. I'll be running a 3 port catch can.

PCV and breather IN to catch can and OUT to turbo inlet

[pcampbell]

On my valve breathers 1/2” work great. Snug and No hose clamps needed.

[sebastian323]

how about this idea - I run a three port catch can with two inlets , one inlet going to the PCV and the other inlet to the valve cover breather lines, and the outlet to the turbo inlet pipe.

EDIT: just read this :

WRONG WAY: Disconnect the PCV<->Inlet line as well as the Crank Vent<->Inlet line. "T" the PCV and Crank vent lines together, and run the remaining end of the "T" to a single nipple on the inlet pipe. Cap the remaining nipple on the inlet. You'll be sending boost into places that definitely shouldn't ever see any. Bad idea.

I don't understand how t-ing the lines together is bad if they both ultimately share a junction at the turbo inlet pipe (which is under suction and not boost from the turbo) can someone elaborate.

also , as I understand vented catch can is not a god idea as it will allow unmetered air into the system

[Peaty]

Might as well put this here ADD W1 CC on 2019 Impreza Sport

https://photos.app.goo.gl/rNGgBQvBkKaiYtjA6

[pcampbell]

Originally Posted by Peaty

Might as well put this here ADD W1 CC on 2019 Impreza Sport

https://photos.app.goo.gl/rNGgBQvBkKaiYtjA6

Blast from the past— I used to work with Kastle (in real life). Do you keep up with him?

[relic48]

Just in case anyone is interested in 1957 "unmetered air" and emissions, scroll down to the 3rd paragraph in the article and look at the picture below it.

https://www.chevyhardcore.com/news/t...c-small-block/