The IAG Performance Competition Series billet aluminum Air / Oil separator (AOS) vents crankcase vapors to the atmosphere. The design is based on years of service on racing and high horsepower Subaru’s. The AOS’s approximate 1 liter capacity, fully heated housing, superior breathing and unique patent pending baffle design sets it apart from the rest.
*May require tuning recalibration.
Notice the large breathing port? At first glance you might think this is excessive, however our reasoning is grounded in simple physics. As air and particles of oil enter into the AOS, the largest particles of oil will collect on the inner surface of the can and drain to the bottom, but the smallest particles will remain suspended in the pressurized stream.
As the air makes its way through the multi-stage baffle system, gravity pulls oil from the air. By increasing the diameter of the breather opening on the top of the AOS, we have drastically decreased the exit velocity of the crankcase vent (CCV) stream. The slower velocity leads to greater oil separation from the pressure stream. A total of 9 mounting holes give the breathing port a full 180° of rotation. On the bottom, a thick Viton o-ring seals the can. Every o-ring in our AOS is formed from Viton which offers superior temperature and chemical resistance.
The side of the Air Oil Separator features 3 port billet hose barbs. There are NO plastic fittings that require thread tape to seal.
The Subaru FA engine has 2 ports that vent crank pressure: two at the top of the block. Each engine vent port receives its own connection to the AOS. By giving each engine port its own entrance to the AOS we have allowed for more effective and faster excavation of crankcase pressure. Additionally this reduces overall system pressure. With a 4″ OD and 5.75″ height, the AOS has an approximate 1 liter of holding capacity. The larger the AOS, the more power you can safely make without having to worry about the AOS overfilling.
The bottom of the AOS is shaped like a snail, redirecting positive crank pressure into the same swirl pattern produced by the 3 side ports. Allowing maximum oil drainage while separating oil from the air in all the venting ports.
Why not use a catch can? Unmodified Subaru’s may require catch can draining as often as every few weeks. Heavily modified race cars may be as often as every race.
Our AOS collects oil and actively drains the oil to the crankcase. The drain port is under the same crankcase pressure as the other ports that are on the side of the AOS. Under normal, off boost driving the weight of the collected oil will easily overcome the pressure in the drain line. However, under heavy boost (especially on higher powered engines) the crank pressure will push back up the drain with the same air/oil mixture that is seen on the side ports. The unique snail design allows the system to breath without disturbing the swirl pattern.
The back plate of the AOS features a unique coolant routing system that heats the entire AOS to the same temperature of the engine. This maximizes the evaporation of any water collecting inside of the can. The hotter the AOS, the less water will collect inside and mix with the oil.
The center bracket allows for adjustable mounting. If your engine bay changes, you can easily change how and where you mount the AOS. A single laser cut mounting bracket is included that fits nearly all applications and configurations.
A laser cut harness relocation bracket is also included. The bracket allows the engine harness connector to be moved forward for additional clearance.
AOS IN THE BOX
Your AOS will arrive to you completely assembled and ready for immediate installation. However, the entire unit can be broken down for cleaning. With a single allen wrench, you can remove 4 bolts and the AOS easily separates into individual pieces.
Q: Why do I need an AOS?
1) Oil vapor mixed with the intake air effectively lowers the overall octane rating of your fuel. The more oil vapor that is sucked back into the engine, the more likely you are to experience engine knock (also referred to as detonation) that can destroy an engine.
2) Oil vapors cause oil & carbon build up over time. The intercooler, intake manifold & intake valves suffer the worst. This oil vapor can create air turbulence that leads to various running issues.
Q: What are the factors that cause oil in crank case vent system (CCVS)?
Q: Are there any risks to using the IAG billet AOS?
Q: What’s the difference between a catch can & the IAG AOS?
*Please note that IAG recommends the STREET SERIES AOS for ALL cars running E85 or high-ethanol fuel blends. When tuning E85, ethanol vapors tend to stay in the crankcase, which ultimately results in the oil becoming diluted and requiring extremely frequent oil changes. Pulling vacuum via the Street Series recirculating design to the inlet is ideal for ethanol tuned vehicles, and will allow the ethanol to be removed from the crankcase and burnt off as part of the combustion process.
Which AOS Is Right For Me ?