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Old 07-25-2015, 11:56 PM   #1
Scooby Specialist
Member Sales Rating: (8)
Member#: 157161
Join Date: Aug 2007
Chapter/Region: MAIC
2007 OBP STI

Default Ixiz Concept: Air Oil Separator

This is a review of the air oil separator made and sold by Ixiz Concept (www.ixizconcept.com).

Installation of AOS

Installation for the AOS was moderate-to-difficult. The instructions were not the best for amateur gear-heads (like myself). Plus, my crankcase and head ventilation system and turbo inlet were already modified by the different shops that had worked on my car in the past. I ended up using both the Ixiz and Crawford AOS instructions (which were step-by-step).

Ming (the owner) was VERY helpful. He responded to all of my emails within hours and also gave me his phone number to call. I spoke to him several times for help throughout the whole process.

I think the original concept was to keep the PCV valve in place and to tie the tee-fitting into the line coming out of the PCV valve assembly. In this method, you use vacuum caps to block off the nipple under the throttle body and the nipple on the PCV valve body. This is the line that recirculates air/oil coming out of the crankcase back into your intake manifold to be burned.

The following sketch is with the PCV valve option. Disclaimer: I forgot to draw a short (2-3 inch long) 1/2 in hose that should connect the valve to the tee-fitting. The tee-fitting won't go into the PCV valve, as shown.

With 22.5 psi of boost and a built short-block, I was not going to keep the PCV valve there. My tuner (Mike "Bad-Ass" Botti) and a Subaru Certified Tech (a friend) both recommended that I delete the PCV and let the AOS do its job. With this method, since the PCV valve was deleted, I ended up fabricating my own "adapter". I used the OEM crankcase vent hose and stuck a short 1/2 inch heater hose into it. The brass tee-fitting then went into the 1/2 inch heater hose section. I zip-tied and or clamped each of the connections here.

This is a more professional diagram I made of my current set-up. Note - Try to keep that 3/8 inch tee as horizontal as possible to help with draining the AOS. Hope the diagram helps!

Easy Upgrades to Consider

I bought this unit used from another member and was missing a few important parts, such as the correct tee-fitting (1/2 x 1/2 x 3/8) for the crank-case vent and a reduction fitting for the OEM hose that goes into the PCV valve assembly. I decided to source the missing parts myself and to upgrade them while I was at it.

I did not like the plastic fittings on the AOS. I went to a local True Value hardware store and spent $10 on three brass plumbing fittings (1/4 NPT male thread with 1/2 inch ID hose barbs). I put some high temperature thread sealant on these bad boys before installing them.

I also bought a brass tee-fitting to use instead of the plastic one I was missing. The fitting I used was a "SharkBite PEX reducing tee 3/4 x 3/4 x 1/2". The 3/4 in fitting doesn't fit the 1/2 in heater hose very easily, but I was able to use a bit of oil to get the hose on all the way. I cinched each connection down with a zip tie. Once you get that heater hose to stretch over this fitting, it won't be coming off.

If you decide to go this route, make sure you know the size differences between NPT, AN, push-to-connect, and flared standards. 1/2 in for one is not the same as 1/2 in other standards. PM me if you need help as I went to a bunch of different hardware and automotive stores before finding the right parts!

I also recommend buying some heat shielding for the hoses or sections that are closest to the turbo and intake manifold, which get very hot. I went on Amazon and ordered a 10-foot package of "Heatshield Products Hot Rod Sleeve" in 1" inner diameter size. It was about $30, but worth it for peace of mind. The 1" was a bit large, but I just used zipties to cinch them down. 3/4 inch may be better, but I don't know.


+ If you buy this kit NEW, it will have everything you need so you don't have to fabricate and experiment (like I did).
+ Many mounting options. It comes with a bracket that can be placed anywhere it will fit, even with only one bolt. I believe Ming also has other brackets for sale as well.
+ Fairly large capacity AOS with good internal baffling.
+ Option to keep or delete the PCV valve.
+ Cosmetically, I think it looks good in the engine bay.
+ Customer service and product support.
+ Lower cost than other brands.
+ Drain hose has a check valve, which will prevent back flow into the AOS.
+ No need to check or discard any waste oil (like a catch-can).

- No option to run coolant lines like the Crawford or Perrin units. Freezing air temperatures could cause oil/moisture to congeal in the AOS, which can clog the system. The moisture comes from the walls of the crankcase. This was a non-issue for me because I have to warm up the car for up to 10 minutes in the winter anyway due to forged pistons. The warming up process should "melt" the yellow gunk, I hope.
- It looks good, but the Perrin AOS comes in a wrinkle red finish, which looks much better.
- The plastic fittings that come with this AOS could leak over time. My used one had threads that were eaten up a bit and the previous owner had put some teflon tape on there to prevent leakage. I wouldn't want teflon pieces getting into my oil.
- Debatable: With the PCV valve deleted, you have to decrease your oil change intervals to about 2000 to 2500 miles. The contaminants/moisture that are normally separated out are going back into the crankcase from the AOS drain hose. These contaminants are burned off through the intake path in the stock setup, or collected and thrown away in the catch-can setups.

I don't have any results yet. I have to put some miles on the car first and then pull the TMIC off again to check if there is still some oil in the y-pipe, TMIC, and throttle body.

I have some other issues that need to be fixed first as well. I think I have a boost leak, which is causing some feedback knock at WOT. I'll post the results after I pull the TMIC off again.

Finally, I took the time to make a schematic of where all my lines and hoses were routed to. This might be helpful to anyone else who is going to install their AOS at home.

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Last edited by nathan.d.kim; 07-26-2015 at 12:28 AM.
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Old 04-30-2018, 02:45 PM   #2
Scooby Specialist
Member Sales Rating: (0)
Member#: 395793
Join Date: Jul 2014
Chapter/Region: Tri-State
2005 92x Aero


I’m looking into one of these. How has held up over time? Did you find improvement in oil consumption/ less or no oil in the intake?
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Old 06-12-2018, 08:17 PM   #3
Scooby Specialist
Member Sales Rating: (7)
Member#: 167278
Join Date: Dec 2007
Chapter/Region: NWIC
Location: Lacey, WA
2018 WRX STI


I ran this in my 2004 WRX for about 8-9 years. solid product practically maintenance free. took the tubing off twice throughout that time and build-up was practically non-existent. it was cheaper to purchase then, but a good investment given the comparable companies.
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