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PERRIN Air Oil Separator Red Stock TMIC (Part Number: )
PERRIN Air Oil Separator Red Stock TMIC (Part Number: )
PERRIN Air Oil Separator Red Stock TMIC (Part Number: )
PERRIN Air Oil Separator Red Stock TMIC (Part Number: )
PERRIN Air Oil Separator Red Stock TMIC (Part Number: )
PERRIN Air Oil Separator Red Stock TMIC (Part Number: )
Community Media
PERRIN Air Oil Separator Red Stock TMIC (Part Number: )
PERRIN Air Oil Separator Red Stock TMIC
Subaru WRX/STI 2002-2007
Read 6 Reviews | 5 Q&As
Part # PSP-ENG-605RD
msrp: $495.00

In stock! Ships same day

Features & Product Details

The PERRIN Performance Air Oil Separator traps oil from the crank case vents before it enters the intake, thus increasing intercooler efficiency and reduces chances of performance-robbing detonation.

The AOS increases intercooler efficiency by reducing the amount of oil deposited into your intercooler and intake system! As blow-by/oil builds up inside your intercooler, the less efficient it becomes due to less heat being transferred away from your engine. This leads to power loss and detonation, which can be damaging to your engine.

Reduce carbon build up in the combustion chamber, intake valves, and in your intake tract. Crank case blow-by is recirculated back to the intake to be ingested by the engine, but in doing so, gets stuck in the intake tract, intake valves, and the intercooler. This builds up over time which causes a loss in power and extra wear and tear on your valve train.

The PERRIN Air Oil Separator is not a catch can. Catch cans capture and water and oil vapor filling with a sticky oily mess requiring it to be emptied. The PERRIN AOS separates engine oil from water vapor and allows it to drain back into the engine. Oil entering from the crankcase vents spins counter clockwise through the entire body of the AOS, passing along four walls equaling roughly 50.25 sq/in of surface area. The multiple baffle walls in our compact design simulate the surface area of an AOS that is 13.5" tall!

As oil accumulates on all the walls, gravity pulls it to the bottom of the can where it drains back to the engine block while water vapor and air merge with the intake air and are reburied in the engine. This means no maintenance or upkeep.

Note: 02-05 WRX will need to remove the Cruise Control Actuator in order to install the AOS.


Color: Red
Installation Hardware Included: Yes
Material: Aluminum
Mfgr. Warranty: 5 Years
Condition: New Product
Return Policy:

RallySport Guarantee - 30 Days

Items that are covered under the RallySport Guarantee offer a 30 day no questions asked return policy.

RallySport Guarantee items may be returned within 30 days of the original invoice date and must include all the original parts and contents for a refund.

The RallySport Guarantee does not apply to products that have been modified, damaged, misused or abused. All returns require an RMA (Return Merchandise Authorization) Number, and freight charges are strictly non-refundable. For more information regarding our freight refund policy, please refer to our return policy page found HERE.
RallySport Guarantee
WARNING: Cancer and Reproductive Harm -



6 Reviews
4.2 out of 5 Stars
5 Stars
4 Stars
3 Stars
2 Stars
1 Stars
Customer Photos and Videos
PERRIN Air Oil Separator Red Stock TMIC ( Part Number: PSP-ENG-605RD)
0 of 1 people found the following review helpful
Perrin a.o.s. 1 year ago
4out of 5stars

In the short time I've had this installed I've noticed my air fuel ratio is gotten better. My oil consumption has gone down the car overall runs better. Also the install does take some time, and if you want to cruise control to work you have to fabricate the cruise control bracket to make it fit. One of the things I noticed that I don't like about this is the plastic fittings it looks like there is an upgraded version with metal fittings unfortunately it's not advertised very well on your site..
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1 of 1 people found the following review helpful
04 STi install 1 year ago
4out of 5stars

Installed on a previously bone stock 2004 STi (USDM), it was undergoing stage 2 upgrades with this install. Overall installation was not difficult, just tedious. I am mechanically inclined and this was pretty easy to understand the concept and get things mocked up. HOWEVER PREP & PATIENCE is key, this install is extremely tedious and always measure twice and cut once since there is not much extra material/hose. NOTE: WHEN APPLYING RTV DO NOT REMOVE THE BOTTOM FITTING COMPLETELY(if you do have fun trying to reseat)!!! Only pull the bottom fitting so its exposed about 1/8" or as specified. After said and done, I really like the functionality and fitment for the most part. It does get pretty busy in the engine bay with all the new plumbing but so far after 500miles i have no leaks or issues.
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0 of 1 people found the following review helpful
04 STI w/ process west mic  4 years ago
5out of 5stars

install took about 3&1/2 hrs for me , I did not remove the throttle body & while in there removed the hot water from the t/b as well . I ran the d/s valve cover hose to the single rear fitting , the pass side to the upper front and the crankcase hose to the lower front . bundled the hot water in/out lines w/ the oil return to help w/ condensation in the line . added 1/4 thick plastic washers behind the mounting bracket , between the strut tower for better fit & to prevent scratching the paint . mounted the alarm system horn/bracket to the lower bolt on the separator . may be making a new bracket to raise the unit up 2-3 as I do not use a strut bar. pretty god kit other than provided hose would not go on to the stock turbo inlet , used some I had laying around . cleaned tmic out and have driven a couple hundered miles so far , a few of which were under load , the grimmspeed 3port ebcs I have on the car vents to atmosphere and after a good flogging on the car oil would be present on the fenderwell , I have not seen this w/ the aos installed so it must be doing something..... i will use for a few months and decide as far as that goes and poss update this review as to the system overall performance .
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0 of 1 people found the following review helpful
Good product, but received a defective item 5 years ago
3out of 5stars

Good product - I chose this over Crawford's design because it can be disassembled and cleaned vs. the sealed unit from Crawford. I also liked the mounting system on this one better because it gave me more flexibility on where to put it. However, the unit I received had bad threads on the straight fittings. They were not 1/4in NPT threads and as a result they would not thread into the fitting on the separator without cross-threading. No, I'm not retarded, I'm an engineer by trade and after testing the threads, I determined the fittings had the wrong thread pitch. I tried working out the issue with Perrin, but that didn't work out. In the end, I invoked the RallySportDirect satisfaction guarantee and returned the item for a full refund. My build has changed in the meantime so I got a refund instead of a replacement, but when I'm ready to purchase another Air/Oil Separator I'll probably come back and get another Perrin unit - and I'll make sure the threads are good before taking my car apart and installing it! I wanted to add that RallySportDirect was AMAZING in every step of the return process. They even called me to make sure that everything was handled alright. Definitely a repeat customer for sure.
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0 of 1 people found the following review helpful
Best AOS for your buck 5 years ago
5out of 5stars

This was one of the best AOS i have ever had! i love perrin and there quality is amazing i have an 04 sti install took me about 2-3hrs just wish that it would come with more clear instructions it jumps from one diagram to a completely different one on the next page. all in all great product!
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  • Q: PERRIN AoS TMIC vs FMIC ? 05 sti  zbnt2 years ago

    I current have the stock tmic on my 2005 sti but plan on going to a fmic setup in future, there is a version for the perrin aos for top and front will it make a difference when i deside to switch to front mount ?
    • 0 of 1 people found the following answer helpful

      A:  Yes there is a version that is designed for a front mount intercooler. PER1 PSP-ENG-607RD will fit FMIC's, and yes there is a difference with where the hoses are being ran as well as the mounting point of the actual AOS canister.

      Chris W. @ RallySport Direct 2 years ago  
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  • Q: location  oh2roundie3 years ago

    I have hear I will loos my cruise control on my 04 wrx wagon due to the mounting point. Is this true? If so, is there a way to avoid it?
    • 0 of 1 people found the following answer helpful

      A:  The cruise control actuator is in the way of where this would be mounted. If you wanted to mount it in a different location, it would require a custom setup.

      Chris W. @ RallySport Direct 3 years ago  
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    • 0 of 1 people found the following answer helpful

      A:  If you go to the iag website, and go to their oil separator instructions it will tell you how you can modify the oil cruise control bracket so you don't have to delete it.

      The vaping champ
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  • Q: RHD  ngian4 years ago

    Hi I'm driving a Rhd. Given the location is where the master cylinder is... I don't suppose this would work for RHD?
    • 1 of 1 people found the following answer helpful

      A:  This AOS would not fit a right hand drive car unless you changed the mounting location, and that may require trimming and/or extending the hoses as well as modifying the mounting bracket.

      Zach G. @ RallySport Direct 4 years ago  
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  • Q: Turbosmart hoses  Danavan5 years ago

    Would it be possible to order some colored turbosmart vacuum hoses to use instead of the supplied hoses? Do you happen to know the dimensions of the supplied or required hoses?
    • 0 of 0 people found the following answer helpful

      A:  We are not able to swap out the hoses in this kit and Turbosmart does not offer all the sizes necessary to replace the hoses in this kit. The hoses that are included with this kit are listed below. (9’) 1/2” Crank Case Vent Hose (3’) 3/8” Fuel Injection Hose (5’) 5/16” Coolant Hose (4’) 5/16” Fuel Injection Hose

      Zach G. @ RallySport Direct 5 years ago  
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