Air/oil separators 101. What sets them apart from catch cans

BiggSean · Posted: Wed Feb 20, 2008 12:30 pm

Air oil separators 101

Ming recently asked me to write an article for him concerning the benefits of an air oil separator system, since the general public still doesn’t have a sufficient understanding behind what the technology offers.

Part 1: How do our OEM setups handle blow-by vapor?

First off, let me explain what blow-by vapor is. Blow-by vapor is a thin stream of oil particulate that is generated in our motors under high amounts of pressure, such as when you are at WOT. This oil vapor seeps past the piston rings, and makes it's way into the crank case. The means by which our motors handle this blow-by, is by redirecting that vapor into our intake tracts, and ultimately into our motors.
The drawbacks of having blow-by vapor re-circulate back into your intake tract are two-fold. You end up with a lower effective octane, and oil consumption is increased.
The loss of octane results, because the oil is diluting the air/fuel mixture into a substantially less combustible fuel. What does this mean for the end user? This means that you are not able to combust your fuel as efficiently as before, and will result in a loss of power, and detonation/knock will be more prone to occur.
The second major issue that occurs in a re-circulation system is excessive oil consumption. All of that oil vapor that is being redirected into your intake tract, is forever lost from your motor. This means that as time progresses, more and more oil is being removed from your system. On track events, it isn’t uncommon for cars to go through a quart of oil at times.

Part 2: How does an oil/air separator work?

An air/oil separator is actually a very simple, yet extremely effective concept. Our motors have a crankcase vent on each valve cover. These two crankcase vents are connected to each other via a T (that long black pipe that you see on the front of your top mount intercooler if you have one), and are then connected directly into your factory turbo inlet. Under vacuum, the blow-by vapor is pulled out of the crank case vents, and is redirected back into your motor via the turbo inlet.
The air oil separator solves this oil consumption issue by taking those crank case vents, and separating the oil vapor from the air. The cleaned air is then injected back into the motor via a vacuum source, and the oil vapor is drained back into your crank case.

Part 3: Why can’t I just buy a catch can, doesn’t it do the same thing?

A catch can is another common item that addresses the same issue, or at least attempts to. The problem with a catch can though, is that while it does improve your octane by removing oil vapors from your intake tract, it does NOT address the overall issue of excessive oil consumption. The oil that is removed from your intake tract is stuck in your catch can, and never gets redirected into your crank case. This means that as time progresses, or under heavy track runs, you are still REMOVING oil from your motor. An air oil separator eliminates this issue by re-circulating that oil BACK into your motor where it belongs.

Mike · Posted: Wed Feb 20, 2008 1:16 pm

Awesome writeup Sean, it's broken down very simple and easy to understand....thanks

metroscub · Posted: Wed Feb 20, 2008 1:24 pm

awesome Sean! I bought that lingeflter form you, but honestly had no clue of its actual purpose.

yopartszach · Posted: Wed Feb 20, 2008 4:30 pm

Very Nice Sean!!

A+

varsitymojo · Posted: Mon Mar 17, 2008 6:58 am

I know understand, hopefully it will get rid of that little extra oil in my turbo and IC

goixiz · Posted: Mon Mar 17, 2008 8:46 am

there are only 3 main way routes for the oil to get into the turbo and then to the top mount intercooler
1. Turbo oil leak internal (unlikely but if it happens you need a new T anyways)
2. Air intake (which has two lines from crankcase and heads)
3. Oil in intake manifold that gets blown pass the TB (just a path not a possibility)

most common is #2
so if you isolate the issue you should not have any oil in the top mount intercooler = better efficiency, and if no oil gets in the intake manifold - less issues (see write up above)

varsitymojo · Posted: Mon Mar 17, 2008 4:53 pm

I think one of my gaskets may be bad. I dont know I am in the process of trial and error.

jma_1000 · Posted: Mon Mar 17, 2008 5:57 pm

great writeup.

Honest Bob · Posted: Tue Mar 25, 2008 11:47 am

Where would someone pick one of these up?

BiggSean · Posted: Tue Mar 25, 2008 11:55 am

Honest Bob wrote:

Where would someone pick one of these up?

Here's a great place to get one. This is probably the most well designed air oil seperator on the market.

http://wrxmodders.com/forums/viewtopic.php?t=10112

IH8PVMNT · Posted: Tue Mar 25, 2008 6:23 pm

good stuff... would this be recommended in general to get one or for mild to heavily modded cars ?

varsitymojo · Posted: Tue Mar 25, 2008 6:28 pm

in general

BiggSean · Posted: Tue Mar 25, 2008 6:35 pm

Any motor that's designed to recirculate blow-by vapor back into the intake tract can benefit from an air oil seperator.

That means all of us guys.

metroscub · Posted: Tue Mar 25, 2008 8:57 pm

They are relatively simple, actually, extremely simple to install and use, I mean, I have never done it, but since I have one, and will need to install it, I imagine I could call my MOM and tell her how to it over the phone...minus mounting the damn thing. I also think it is great, because you could point to it and tell ricer-touge-kids that is like a power cannon that warp reality and propels the mass of air into a super compressed unit of mass and then accelerates it into the turbo.

kh15 · Posted: Sat May 17, 2008 3:56 pm

i got my ixizAOSEP in the mail today and it looks awesome! ming really put together a nice product!
....one thing though how exactly do i install it? i dont know where all the hoses go