IAG Air / Oil Separator (AOS) For 2008-14 Subaru Impreza WRX & 2008-21 STI
IAG Air / Oil Separator (AOS) For 2008-14 Subaru Impreza WRX & 2008-21 STI
IAG Air / Oil Separator (AOS)
The IAG Performance V3 Street Series Air / Oil separator (AOS) is an excellent investment to keep your Subaru vehicle running well. The Street Series AOS maintains OEM PCV system functionality, but supplements its capacity. The Street Series AOS design is based on years of extensive testing on standard and competition applications. The Street Series AOS' large, 1-liter, cast aluminum swirl pot canister more effectively separates oil from the PCV system upstream of PCV gasses return to the intake system. The Street Series AOS' fully-heated cast aluminum housing, superior venting, and unique, patent pending, baffle design set it apart from the rest. The Street Series AOS is compatible with all fuel types, extends engine life, improves crankcase ventilation and is compatible with standard ECU calibrations.
Keeping Oil Out
Keeping oil out of the engine intake tract is extremely important towards preventing premature mechanical failure and maintaining performance. Oil in the intake tract of the engine has several detrimental effects. First, the oil coats the internal portions of the intake, intercooler, and piping. This oil may cause premature failure of rubber or silicone hoses, which leads to failed connections.
Once the oil reaches the intake tract it will directly enter the intake manifold and then the combustion chamber of the engine. Oil inside of the combustion chamber can cause detonation and preignition, high emissions, smoke, loss of power, decreased gas mileage, and even catastrophic engine failure leading to expensive repair bills.
The Street Series AOS maintains the OEM PCV system functionality, but supplements its capacity. The Street Series AOS PCV discharge gasses return to the turbo inlet, retaining a PCV valve to draw additional suction, improving air oil separation. The Street Series AOS protects from oil dilution and lubrication failures in ethanol fueled application because the Street Series AOS captures fuel vapors out of the oil and returns these vapors to the intake tract for combustion. The Street Series AOS protects from both oil entrainment in the intake flow and oil dilution in the engine's lubrication system far better than the OEM PCV system alone.
Version 2 vs Version 3 IAG AOS
The most popular Subaru AOS is now even better! The IAG AOS body is completely redesigned using cast aluminum and features an integrated coolant passage for better heat retention. Additionally, the V3 AOS heating system is upgraded by relocating the coolant lines to the bottom of the body using new swivel fittings, heat sleeving and an integrated coolant bleeder. These heating system upgrades will allow for a cleaner installation and less condensation buildup in colder climates. The new compact body has the same 1-liter capacity as V2, but features a sleeker design and adds removable ORB fittings for greater versatility.
- True 360 Degree Rotating Breather Port
- Dual Breather Ports
- Greater Pressure Stream Oil Separation
Notice the dual breather 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 overall volume 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 20 mounting holes enable the breathing port a full 360° of rotation. On the top, 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.
- Compact Cast Aluminum Design
- Approximate 1 Liter Holding Capacity
- Integrated ORB Ports
- Aluminum Body is powder coated in Red or Black Wrinkle Finish
- The side of the AOS features 3 -8 ORB removable billet hose barbs.
The Subaru EJ engine has 3 ports that vent crank pressure: one on each cylinder head, and another on 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 IAG has allowed for more effective and faster excavation of crankcase pressure. Additionally, this reduces overall system pressure. The AOS has an approximate 1 liter of holding capacity. The larger the AOS, the more power you can safely make in competition applications without having to worry about the AOS overfilling.
- Unique Baffling Controls Crankcase Pressure
- Returns Oil To The Engine
- No Maintenance or Manual Draining Required
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. This allows maximum oil drainage, while separating oil from the air in all the venting ports.
Why not use a catch can? Catch cans require regular maintenance and manual draining for proper operation. If the catch can is not drained often it may reintroduce oil into the intake when it overflows or create a mess in the engine bay.
The IAG 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 competition 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 breathe without disturbing the swirl pattern.
AOS DRAIN PORT
- The AOS drain port is able to be rotated for ease of installation, as well as pre-threaded to accept an ORB fitting if desired.
- Includes all fitting required for installation
- Includes unique billet aluminum coolant swivel fittings
The supplied coolant hose is built to SAE 30R9 standards. It will withstand coolant temperatures of +257°F.
The oil vapor hose is designed to withstand oil and fuel vapors, exceeding SAE J30R7
- Heated By Engine Coolant
- Reduces Moisture & Oil Mixing
The body of the IAG V3 AOS features an integrated coolant chamber that heats the entire AOS to the same temperature of the engine. This cast aluminum can holds more heat which maximizes the evaporation of any condensation collecting inside of the can. The hotter the AOS, the less condensation will collect inside and mix with the oil.
- Multi-point Adjustable Mounting Bracket
The center bracket allows for adjustable mounting. If your engine bay changes, you can easily change how and where you mount the AOS. The V3 AOS body features a greater number of mounting holes enabling a wider range of adjustment. 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
- Ready To Install
- Hardware, Lines & Fittings Included
- The AOS arrives 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 two bolts and the AOS easily separates into individual pieces.
Q: Why do I need an AOS?
A: In stock configuration, the un-baffled crankcase pressure is re-circulated back into the intake stream.
This can be harmful for two reasons:
- 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 the crankcase vent system (CCVS)?
A: There are a variety of factors that determine how much oil will be in the CCVS. The most significant of these factors are boost pressure, piston to cylinder wall clearance and oil viscosity. Smaller factors include ambient temperature, engine temperature, piston ring condition, and valve guide condition.
Q: What's the difference between a catch can & the IAG AOS?
A: Catch cans are an air/oil separator that does not actively drain the collected oil back into the engine lubrication system. Most catch cans require you to drain the contents out manually. By nature, a turbocharged boxer engine will produce significantly more oil in the CCVS than other engines of similar displacement.
Q: Which AOS is right for my vehicle?
A: The Street Series AOS maintains or improves the functionality of the original PCV system and may be installed on street driven vehicles subject to EPA emissions standards. The Street Series AOS provides optimal oil separation and venting performance for vehicles, including unregulated competition applications, up to 600 WHP and those fueled by E85 or other high-ethanol fuel blends. The Street Series AOS protects from ethanol caused oil dilution and resulting extremely frequent oil change requirements. Pulling vacuum via the Street Series recirculating design to the inlet is ideal for ethanol fueled competition vehicles, removing ethanol vapors from the crankcase and returning them to the intake system for complete combustion. Please note that the IAG AOS is not compatible with most aftermarket strut tower bars.
Competition Series AOS are “Competition Only” components for installation exclusively on “Competition” vehicles or “Racing” vehicles not subject to pollution control. IAG recommends the Competition Series AOS for Competition vehicles with greater than 600 WHP output. The Competition Series AOS prevents any oil suspended in the PCV gases from re-entering the turbo inlet but requires calibration or tune changes. Select a Street Series AOS if you prefer not to retune your Competition vehicle for this upgrade. For Competition vehicles, follow your engine builder’s maintenance directions, but perform oil changes before every race or practice event .
IAG is not offering any Competition only components for installation on street driven or regulated applications. Installing a Competition Series AOS on a vehicle other than a Competition vehicle used solely for competition motorsport may be violation of the federal prohibitions against “Tampering” provided in CAA§ 203(a)(3)(A), 42 U.S.C. § 7522(a)(3)(A), 40 C.F. R. § 1068.101(b)(I) and “Defeat Devices” in CAA§ 203(a)(3)(B), 42 U.S.C. § 7522(a)(3)(B), 40 C.F.R. § 1068.101(b)(2).
* The IAG AOS is not compatible with most aftermarket strut tower bars.
PDF Instructions for 08-14 WRX / 05-09 LGT
PDF Instructions for 08-14 STI
PDF Instructions for 15-21 STI
* The IAG AOS is not compatible with most aftermarket strut tower bars.
Model Year & Fitment
- 2008 Subaru WRX
- 2009 Subaru WRX
- 2010 Subaru WRX
- 2011 Subaru WRX
- 2012 Subaru WRX
- 2013 Subaru WRX
- 2014 Subaru WRX
- 2008 Subaru STI
- 2009 Subaru STI
- 2010 Subaru STI
- 2011 Subaru STI
- 2012 Subaru STI
- 2013 Subaru STI
- 2014 Subaru STI
- 2015 Subaru STI
- 2016 Subaru STI
- 2017 Subaru STI
- 2018 Subaru STI
- 2019 Subaru STI
- 2020 Subaru STI
- 2021 Subaru STI
- 2005 Subaru Legacy GT
- 2006 Subaru Legacy GT
- 2007 Subaru Legacy GT
- 2008 Subaru Legacy GT
- 2009 Subaru Legacy GT
I was so used to having catch cans that I decided with this Subaru I wanted to go a different way and get an air oil separator. The thing I like the most is it's no servicing involved like a catch can and it will help save on the engine.
Fast shipping. Amazing product in perfect condition. No trouble at all with my purchases from iag. Look forward to more business with them
Definitely the best product as a 1st mod for your Subaru.
My tech at Performance Auto Solutions also thinks this is the best choice out there.
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You have 14 days to inspect your shipment and contents. After that period, IAG is no longer responsible for missing items. You have 30 days to report any damaged or incorrect items, after that period IAG is no longer responsible for returns or exchanges. All stocking products are subject to a 30 Day return policy. The item(s), when approved for return, are subject to a 20 percent restocking fee. Canceled orders may be subject to a 20 percent cancellation fee. All product returns require a return authorization number before being shipped back to IAG or the manufacturer. An “RMA” number is obtained by calling the IAG Support Desk at 410-840-3555 or emailing firstname.lastname@example.org. Some products may require shipping back to the manufacturer for inspection before a return or exchange may be processed. Some products may not be able to be returned. Products that have been modified or installed are not eligible for return. There are no returns or cancellations for Special Order/Made to Order items and Electrical Components (including the COBB Accessport). Items returned after the 30 Day return period without an RMA will be refused. Canceled service appointments with deposits are non-refundable.
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IAG Performance Product Warranty (Excluding - Short Blocks / Long Blocks)
This limited warranty gives you specific legal rights and you may also have other rights, which vary from state to state. We limit the duration and remedies of all implied warranties, including, without limitation, the warranties of merchantability and fitness for a particular purpose to the duration of this express limited warranty. Some states do not allow limitations on how long an implied warranty lasts. The remedies described below are your sole and exclusive remedies and our entire liability for any breach of this limited warranty. Our liability shall under no circumstances exceed the actual amount paid by you for the product, nor shall we under any circumstances be liable for any consequential, incidental, special or punitive damages or losses, whether direct or indirect.
This warranty covers defects in materials and workmanship of your IAG Performance Product for 12 Months or 12,000 Miles from the date of receipt.
IAG will repair any IAG Manufactured Product that proves to be defective in materials or workmanship within the warranty period. If a repair is not possible, we will either replace your Product with a new Product of similar composition and price, or refund the full purchase price of your Product, at our sole discretion. There is no charge for inspection but the buyer is responsible for shipping charges.
IAG Performance Engine Warranty
For more information concerning our engine warranty please visit IAG Performance Engine Warranty Page
Other Manufacturer Products:
Products not manufactured by IAG are subject to the individual manufacturer warranties which may apply. If you have questions concerning the fitment, appearance, or performance of your item, please contact a member of our customer support team for assistance.
Our customer service team is happy to assist you with the products purchased from IAG Performance. Our support associates can help you with installation support, troubleshooting advice, and help to identify possible manufacturer defects.
For products that are found to have defects, our support department can provide the contact information for the manufacturer to arrange a warranty inspection and, if applicable, any necessary repairs or replacement shipments.
You may also contact the manufacturer directly for information regarding product eligibility and specific terms and conditions of warranty coverage.
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