Air oil separator vs. catch can

[snowdog]

Hey all,

Just wanted to get some idea of what people are running and why?


Air oil separator


Catch can


Double catch can


nothing

[DAEMANO]

PCV Side - Mishimoto Catch can w/ Boomba check valve
CCV Side - Nothing, but a vent-to-air separator or second catch can would probably be a good idea.

[xkalelx]

I guess I don't understand the difference between an AOS and a catch can. Can someone please elaborate?
@DAEMANO, What does that Boomba check valve do exactly? Allow oil to drain back to block?

[DAEMANO]

Originally Posted by xkalelx

I guess I don't understand the difference between an AOS and a catch can. Can someone please elaborate?
@DAEMANO, What does that Boomba check valve do exactly? Allow oil to drain back to block?

I've seen the term "catch-can" and "air/oil seperator"(AOS) used interchangeably. IMO they could semantically be slightly different. A vent-to-air style catch can, doesn't really intend to catch the blow by (that mixture of oil, water, and contaminants) but instead to remove and release it. So this arrangement is more of a true AOS. I could have that totally wrong, but whatever

A check valve helps prevent PCV failures, leaky gaskets, and blown seals caused by excessive pressurization on a boosted vehicle. Since our PCVs were designed for NA and not FI, a check valve is a cheap ($20-30ish) bit of insurance here.

[TylerLieberman]

In EXTREMELY short:

Catch can will catch the oil and hold onto it, meaning you'll have to check the contents and empty out occasionally.

Air Oil Seperator will seperate and then return through the engine.

[myioz86]

Double catchcans two seperat systems drain it out and through it away dont want this oil,fuel mix going back into your oil supply.

[wbradley]

I use a Cusco vehicle specific catch can with stainless steel wool that I stuffed inside. For the 2 weeks I ran at max 9 PSI on my HKS blower it accumulated a tiny bit of oil and I can see no oil inside the throttle body indicating the crank vent doesn't need oil retrieval.

[Weapon86]

for N/A single catch can (PCV to manifold) should be enough unless you track often. if boosted, i suggest getting a dual catch can.

[spitfire481]

dual 42 draft design cans vented to atmosphere

[Grip Ronin]

i dont really get the difference in what your asking lol im running the phastek catch can the separates the air and oil but vents the air back to the engine instead of the open vent. you still have to empty the can tho