How an Air Oil Separator Works and Why You Need One!

In this video Mike takes a look at the IAG Air Oil Separator for one of our Subaru projects, explains the difference between an AOS and an oil catch can, and tells you why we think all turbocharged cars NEED one!
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[@gadielvenegas5120]

This comment is to help the algorithm! Mike is like that neighbor you help out once cause he’s always working alone then you end up spending hours with him cause you find out he’s a great guy and has an immense wealth of knowledge! Glad y’all decide to make these vids

[@rapid946]

Nobody asked for you, but we could not be more happy you exist. You are currently saving me thousands 😂 THANK YOU

[@TheCaptainbigboy]

I could listen Mike explain anything and it would be simultaneously soothing and entertaining

[@stevemcrichards8768]

I like Mike he's got a good delivery and really goes into the details and gives real world application experience for the products.

[@jason.arthur.taylor]

He's #1 in the world. What else would you expect?

[@colemartin7804]

I've always heard an AOS was important in turbocharging. I know that it is pretty self-explanatory. Its obviously a device that separates air from oil but the detailed breakdown of this part, how it actually works and the explanation of "blow-by" were on point man! Thanks for all the insight and hard work you guys put into you videos....Very informative...I like the way you make simplicity out of complexity...

[@dukecraig2402]

Even better, and the next step up for doing the job, is a vacuum pump on the engine's crankcase, the only one's I've ever been around are mechanically driven, either as original engineering or as a performance upgrade, heavily boosted engine's practically require them, I'm talking aircraft racing engine's that make 100 psi of boost, an engine like that will load up the crankcase with so much oil mist it'll drag big power off anything that has to rotate through it. There's even some normally aspirated engine's that'll benefit from a vacuum pump, Harley's have always had bottom end breathing problems when built for high revving performance, for years every race team in Grand National racing has used mechanically driven vacuum pumps on the bottom ends of the Harley XR750 racing engine's.

[@resurrectedautoworks9781]

just picked up my first subie and it had developed alot of issues right off the bat, this channel has helped me understand quit a bit about these cars and just stuff in general. great channel, thx for putting it on

[@Thaib0xer69]

Excellent and thorough review of this piece of gear!!! Super technical, but you laid it out in layman's terms for even the novice enthusiasts to comprehend. I love my IAG SS AOS!!!

[@mitsuturbo]

I love this guy's whole demeanor and manner of speaking. Feels like I'm sitting down with a knowledgeable friend or colleague.

[@htthepunk]

Another great video! The heated feature is interesting. I imagine that it really helps flash off more water and fuel vapor that way, not to mention speeding up oil return. Thanks for bringing us a in depth look!

[@justinturner4850]

I’m very grateful to you guys for taking the time to make these videos! I love to learn as much as possible about this hobby.

[@etjo7338]

You guys really know your stuff! I like that you guys actually explain your reasons for part choice rather than just listing them off

[@Darthreloy]

Why do I just love this guy. Brilliant, nice, friendly feels. Its not normal, but in a good way.

[@RicerX06]

Mike Kojima is such a boss. If i wasn't dirt poor I'd have them work on my shit until then I'll keep rolling around on cold concrete

[@lazylegs15]

I wish you were my automotive teacher. So easy to listen to and pay attention

[@Mark-ks9jj]

A great explanation of the features of this oil separator. Im running a non-turbo E25 in my 2009 subi forester & was surprised at just how much oil was collecting in the air box, this explanation really clarifies the root causes of some of my issues. Thank you. pity you arent in Australia.

[@goudagramps3719]

Just installed mine yesterday everyone keeps asking me what it does and I hear if u can’t explain it to someone else you don’t know enough about it…thank you sir

[@infernomaster2702]

I have Tracey Lewis's - Air Oil Seperator on my 6th gen camaro. It is SOOOOOOOOOO good, I would say even normal Direct Injection cars even not meant for performance should have something similar installed. These GDI engines can break down very easy due to blow by build up. People just dont know how helpful these things are.

[@rolberg]

Mike can make anything sound super interesting!

[@Thechriskraft]

Appreciate you telling the difference between this and a catch can.

[@ToyotaCam]

I have a poster of Mike in my room so I remember to smile every day

[@FTGMotorsports]

I have used a variety of catch cans mostly on SC and Turbo LS' cars. I can see why this is a step above thanks to your excellent description - something I need to try out on the next build - thanks

[@davidpelayo2058]

So awesome Ive always wondered what a catch can was for and now I want an oil separator for my project thanks for the explanation!

[@arzynistic]

The absolute giddiness and joy you express talking about this just makes me smile. Excellent and informative video 👍

[@31Kittystyles]

You’re a good teacher. 7;39 was my favorite part.

[@TheAverageAcerage]

So glad I found this guy

[@rowland.]

I have to install one of these for a buddy of mine tomorrow and had no idea what I was doing or how this thing worked. Now that Ive watched your video and explanation I understand why different ports are in specific places and I think this video will help me a lot with the install. Thank you for this great video

[@rowland.]

Update, the bolt securing his intercooler to the turbo flange snapped😃

[@darrylcavanaugh9465]

Wow. Proof no one ever stops being a student. I have a few projects that will have your A/O separator incorporated into their systems. Keep educating us!

[@ovalwingnut]

We loving us some MotoIQ. Thank you!

[@irvingsanguinetti7659]

This fella has a grin like its is 1st time in front of the camera. Every video lol. Perhaps he's a happy guy.. very knowledgeable. 👍👍👍👍

[@jaredwhite2521]

I love this guy. He always looks so happy explaining. Very knowledgeable too 👍🏼

[@januarioqueiroz3122]

I love him too!!

[@ApolloWRX23]

You explained that so perfectly! Thank you for the information and in depth explanation of how this gem works. Just placed my order for my 2023 WRX!

[@beaches2mountains230]

I CAN 1000% AGREE WITH CATCH CANS FOR ESPECIALLY FOR BOOSTED SUBARUS !! IF YOUR MOD'N A BOOSTED SUBARU IT SHOULD BE ON YOUR TOP 5 PARTS LIST, IF YOU WANT YOUR BUILD TO LIVE LONG RELIABLY. I UNFORTUNATELY LEARNED THIS THE HARD WAY BACK WHEN I WAS YOUNGER AND ONLY THOUGHT ABOUT HP AND VAGEEN.

[@VALINTYNE117]

im so glad i found this channel

[@craigbarrett2278]

Rebuilding my shop rebuilt ls motor myself after very low mileage, who knows...... But going forged pistons etc now to turbo in two years or so. This made total sense and will be a good add to my build.

[@00imprezaRS]

My EJ257 with forged pistons could fill 2 catch cans (one for head breathers and one for PCV) in a single 20 minute track session and loved to drink oil. After installing the IAG AOS it returns almost all that oil back to the crank, and doesn’t need topping off newly as much. This product really does exactly what you said.

[@Lemon8id]

Im installing one on my vb soon. Thank you for the insight. Very informative 😁

[@crosse73]

I could listen to Mike all day! It’s like a mini degree just from his knowledge transfer

[@E85_STI]

I had radium dual catch cans while I was on 28 lbs of boost and now that I’m on 40 lbs the catch cans fill up quick with fresh oil so I threw on an AOS and I’m sure it works well but idk as it drowns itself back into the back of the block. It’s essential for sure. I’m also running the competition AOS so for those with a Subaru if you are not on a speed density tune run the street series as the competition is not meant for a stock PCV system.

[@roberturquides-swann4953]

You guys kick ass , I couldn't be happier with the content. Thank you !

[@matthewferreras7181]

Thanks for the video. I liked seeing it apart. I have one but never dismantled it. Great explanation!

[@dannyve4982]

First mod I did on my STI back in 2017 - albeit the Crawford unit. Highly recommend an AOS on your turbo Subaru. Great video Mike. Love the constant perma-smile as always CheeRS!🤙🏻

[@motoiq]

The Crawford is also a good unit.

[@varsington]

Hey danny, i have a 2018 sti,, stock aside from hks suspension, and awe track edition exhaust. How has it helped your 2017 sti?... What happens if i don't get one.

[@dannyve4982]

@@varsington potential blowby gases from crankcase ventilation that will end up in your intake track. Most noticeable in your intercooler. Good way to check: take the coupler off the intercooler and run your finger inside, if you have an oil presence, you have blow-by. The AOS will help mitigate this. Helps in hot climate and those who track their cars. If you live in the northern belt for it gets cold, it can have a negative effect during either months as lines can freeze. Some run the IAG with the coolant lines to mitigate this. I never winter drove mine, so no issues. I highly recommend an AOS for engine longevity. Cheers

[@billyrosewood5474]

I love watching your explanations. Would you be able to do a video on the FA20 BRZ/Toyota 86 engine? Outlining pitfalls or things that can be done to improve reliability?

[@motoiq]

Its pretty much the same as our EJ videos but maybe even worse!

[@ShutUpandShift]

This, but with the FA20DIT from the WRX. I have a feeling much of it will be a carryover to the new FA24.

[@cctrans29]

I installed one on my 2018 WRX. My oil level stays normal. Don't have to add half a quart between oil changes. That Motul oil is expensive 😢 So the IAG AOS saves me money 💰

[@arrodlaroque]

Amazing explanation of the AOS, especially each component

[@Andre_The_Drek]

Very cool product and the heating feature is great.The only potential issue I saw are the "fins" in the bottom seemed to have quite a few burrs left after machining. 🤷‍♂️It honestly may not even matter if the oil is being filtered enough before getting returned, just not a fan of leaving burrs on anything is all. It could just be pixelation on my end too. 🤷‍♂️🤣 Anyway, great video.

[@lnengineeringllc]

Great job Mike! Excellent explanation of how an air oil separator works!

[@motoiq]

Thank you for watching!

[@baonguyen9035]

Thank you, good info. I replaced the one in my Porsche. Will look into putting something like this. Thanks again 😊

[@RicondaRacing]

I got my IAG comp series AOS, actually getting it installed tomorrow!

[@brendenrushing6580]

Didn’t even think about quality between AOS! Definitely going with the IAG

[@luckyulivhi]

This will solve a lot of my worries about venting my valve covers and crankcase that my oil catch can just doest do and no need to check oil level in can anymore. Its worth the $.

[@MicroTurboComplex]

This dude is always geekin

[@Nevoexpo]

Amazing. I love the explanation Mike gives and how to the point he is. Thank you so much for sharing.

[@captainchaos3053]

Back in the day we called it a swirl pot. It was really only necessary on super highly tuned engines and stopped the crankcase emmissions from contaminating the intake charge. Were i live we are not allowed to vent to atmosphere. It also returned the oil back to the sump. A catch can was only used for race cars.

[@motoiq]

A swirl pot is part of the cooling system used to take bubbles out of the coolant.

[@captainchaos3053]

@motoiq Well I won't argue the point because it won't get us anywhere but when I was a youth running turbocharged cars that was the common term used because the oil is literally swirling around inside. The point at which bubbles are formed in the coolant the engine would be in serious trouble because that would mean the coolant is starting to boil. In which case it would vent from the pressurised system and into the header tank which has a lower pressure breather cap to allow air to escape. But I still like you're videos and find them quite interesting.

[@motoiq]

You would not want to do that because you would lose oil pressure. You should not have active pressurized oil flow in an open swirl pot-type device. Google swirl pot and every single thing that comes up is for de-aireating coolant, not oil. We use these in just about every serious race or drift car. They make a huge difference. Race engines have localized boiling and these get rid of the bubbles. This is an air oil separator because it gets the oil out of the blowby gasses and returns it to the crankcase.

[@captainchaos3053]

@motoiq I understand you're point im just saying where I live we called these swirl pots because of how they work. You will also find some people calling a fuel surge tank a swirl pot and that's not strictly correct either. The devices we used for air oil separation were not under pressure as they were external to the engine. They just caught the vapour from the breather system and returned the oil to the sump by gravity.

[@motoiq]

Ok it's the same thing just different semantics.

[@25kmgb]

Another excellent explanation- thanks Mike!

[@Daymow]

That’s why the IAG separator is so good!! They do such a good job of getting rid of the milkshake! Love the channel 🤘🏻

[@auomwehttam]

Great video Mike! I've been meaning to get an AOS on my WRX. On a side note, I've been working with Simon K. at HMA. Was hoping if we could come tour your place but I'm not sure if he can fit that into his schedule as he's a super busy guy. Anyways, thanks again for the great content. Perhaps you guys could cover how to build an FA motor that won't blow up sometime?!

[@Jdmjunkie001]

The Verus AOS has a drain back option, at least for the FA20.

[@BadJo0Jo0]

Love mine. Installed with coolant kit. Then never have to worry about it

[@not12listen]

Helping that algorithm! I'm curious about adapting this to my GR Corolla... 25psi of boost is quite a bit of stock car. :)

[@vegetapompa4551]

You have the best way explaining anything, i admire that sir.

[@persiorak20D]

Love how he smiles the whole time

[@matthewbolton4289]

the best thing i put on my iag built long block in my 2005 sti

[@MrSiDeWaYs240]

Need a full kit for the new direct injection vehicles .. they are coming in at 20k miles with rough idle an gunked up intake manifold , throttle body ,etc ! This definitely no looks like a high quality low maintenance product with will be great for the consumer ‼️thanks for the info guys

[@DJ_Driven]

Unfortunately the direct injected motors bypass the valves and do not allow for self cleaning like port injection. Pretty much would have to upgrade to a di/port injection aftermarket kit to solve that problem.

[@johnmurraycompton569]

Really like the way you explain things. Your ease and comfort on the subject matter illustrates your deep knowledge.

[@teehranfrancis4707]

Such wholesome and informative content! Keep up the awesome work

[@zosxavius]

Video idea: Now I want to hear Mike talk about engine layouts now and their effects on blow by and oil distribution. I never considered that a flat engine would produce so much oil from the crankcase breather, but it makes sense. All of my motorcycles have flat engines because they are all Goldwings. They generally do not consume much oil if any, but at high rpms they will lose some oil.

[@Grimgrak1]

Are your goldwings turbocharged? Didn't think so

[@Thunderstryk]

this AOS is the first mod i put on my wrx. best thing i did! especially helps with keeping down valve carbon buildup on the FA20DIT

[@mikecenteno7292]

I love how happy he is.. really loves what he does

[@fredhuston7865]

Mike is so good at explaining things in a carring manner, if I ever get sick, I want him to be the one who tells me I'm going to die !

[@motoiq]

I hope you won't!

[@backnunAndy]

I didn't know differences between regular oil catch can and this particular product! Good to know of it! Thanks!

[@240Tony]

thank you sir! i know what to get now, my 240sx rebuild will be the cleanest!

[@hedbanginhippi]

If you plan on installing a bigger intercooler better leave those connections pretty long, just had to reroute some lines for that purpose

[@muasboy]

He’s an asian hotrod guy. And the cars in the background says it too lol. Love the channel. Keep the vids coming

[@frankies.4500]

This guy is great at explaining complex mechanics and machinery to us layman. Thanks man! 👍

[@dukecraig2402]

I know, and he's always so happy, he's got that perma-grin on his face all the time like every day he had sex the night before.

[@I_know_what_im_talking_about]

His constant grin is extremely annoying to look at. Like why is he CONSTANTLY Smiling?!?! Wtf. 😒

[@frankies.4500]

@@I_know_what_im_talking_about He's happy. This can be confusing to most humans these days. 😅💀

[@Blyatarina]

Great review of the separator. I look forward to adapting one to my track Z and get away from the open, vented catch can.

[@bradgreen987]

My '16 WRX modified would have blown without this specific item. The blowby was intense. Tuner told me coolant heated separator only way to go. Thx

[@loligagger85]

there are 2... oil catch cans i have used before that do return oil back to the engine, one uses a pump, the other a check valve that works well with a NA CCV pulse. BUT its not close enough to do anything he is talking about.

[@imnotsurewhy]

The LEGEND, The GOAT, Mike Kojima

[@luigimastropasqua674]

Thank you for that information. We are getting started on a marine engine. 572 dart block 12.5 cr. The camshaft rpm limit is 8500k running on high test fuel. We have had issues with moisture and contaminated engine oil in the past with a stock 502 .Thinking about a vacuum pump for battling this condition . Now, watching this video, I was wondering about the catch can your takling about. Do you think it can handle the job instead of a vacuum pump ?

[@motoiq]

This isnt a catch can, it returns blowby oil to the crankcase. A vacuum pump still probably needs something like this on the scavenge side. Vacuum pumps can increase power.

[@changodrift]

great video, I was about to ask About the E-85 Mixture that i wouldn't want back in my Engine but you then answered it my Question.

[@Shawnspawn315]

A+ i feel so educated listening to him explain things.

[@pn7064]

I've learned so much from your great vids. Love Mike's communication style, always end up with a smile on my face at some point during the vids.

[@itsreallytom4310]

I don’t really need one of these but that smile makes me want to buy one

[@weduhpeople8504]

My 04 sti when I owned one had dual catch cans. I did alot of wot runs which I noticed a large amount of blowby fluid in the catch cans which had to be emptied frequently.

[@JHS818]

love this man. car guy through and through. Always a smile in his face when he talks about cars.

[@rotorblade9508]

best design I’ve seem so far 👍 cars actually have an oil separator basically the valve covers have baffles of various design so most of the oil simply falls back to crankcase then the air is vented to the breather tube and pcv on the other side. The interior of the valve cover is obviously hot so will not condensate. However, sometimes you need to recover more oil, if it’s well designed an additional oil separator will recover more or it may be even more effective than the stock. Large tubes for adequate flow is very important to prevent damage of gaskets other benefits you mentioned. I’ve also heard a negative ccv word be beneficial but It still needs fresh air to come in so additional vaccuum under acceleration would be beneficial

[@jwsfoulke]

Great Info! Keep this type of content coming! This seems like a win/win, why does Subaru deny warranty if you have an AOS? I can't see how this would cause any other component to fail.

[@DJ_Driven]

If the AOS is installed correctly they cannot void the warranty Subaru would lose in court.

[@jethrot100]

Looks like a damm fine product to me. I dont think I would return the oil to the sump. Probably have to at the track though.

[@RobertFeher30]

I want one. Great information and thanks for it!

[@driftkingification]

thing cost almost $500 thats nuts!

[@JuanWick2010]

You guys at MotoIQ are the Neil deGrasse Tysons of the automotive industry 🤣. You explain everything in a way that everyone can understand what’s what 👍🏼

[@Bones12x2]

Except Mike isn't an annoying clout chaser that uses his expert status to share his opinions on things he isn't an expert on like Neil.

[@Bobo-ox7fj]

I would be distraught if anyone referred to me as the Neil deGrasse Tyson of anything at all. What an insulting thing to say to such a helpful, intelligent group.

[@SBahamondes]

You mean narcissistic asshole?

[@Smirnoff67]

We get it, you reddit.

[@Uno_Floydd]

@@Bobo-ox7fjI would also venture to say stick to your major.

[@nialoupa1765]

Great video! I always learn something new, and you seem like a really nice guy!

[@TheSteve1175]

Dude, I have the bell turned on, been subed for a long time and here I see 7months ago you posted this. Wow. Be Blessed and Be Safe 😇

[@motoiq]

Come on by and check out what we are doing from time to time!

[@triplemotor]

Excellent Mike......

[@snfpagp]

Great advice

[@BOOYAGA]

From today, this is going to any engine/car I'll ever build, thanks ✌️

[@tomsellout9576]

I have an RB, probably need one of these. Might’ve saved the first engine

[@ThatGuy-yj3lu]

Statement & question (05 Forester XT w/built motor) I've never liked the idea of returning what an AoS catches from the crankcase blow by. Personally, I use 2 Radium baffled catch cans with no return in my PCV system, before returning to the turbo inlet. They've served me quite well. It may be my lack of understanding or even research with the return style AoS', but: With the heated can, is it guaranteed that nothing but oil is being returned to my crankcase? Have any oil analysis tests been done to legitimize heated return style AoS' (whether it be Radium's, IAG's or Crawford's)? I.e. oil degradation between stock PCV system vs. return style AoS vs. no return AoS? I'm sure there'd be a lot of variables in a long term test such as this, but I imagine it would provide some good ball park data against each setup. I love the maintenance free concept of the return AoS', I'm just not totally sold on them. Emptying my catch can setup (not very often), and checking my oil once and a while is a minor hassle in the grand scheme of my peace of mind.

[@motoiq]

If you have seen cars fill up catch cans then blow the motor due to oil starvation you would not be so anal about returning oil to the crank case! In that case your unseparated OEM PCV system is a far worse offender than what comeS back to the crank from this AOS.

[@NSWvet83]

Man, just found this and subscribed and been watching video after video! Good info!!! Building an HR 350z and 98' Z28 and this stuff it's really helpful with future decisions. Like not installing my long tubes, since I'm going to put turbos on. Keep up the good work!

[@09BertoSS]

Maaan, I’ve been saying I’m going to get this for my WRX since I got it almost 8 years ago lol

[@jgboarder]

Thanks Mike!

[@SeanzSS]

I really love your videos, your explanations are great and concise. Keep it up!

[@motoiq]

Thank you very much!