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'do right & fear no one"
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Discussion Starter #1 (Edited)
there are six aos manufacturers that are typically referenced on iwsti. these are the links to the manufacturers' respective sites. the first four are in no particular order. i placed moroso and element last. i left all the detailed information entirely up to the manufacturers to explain on their own product pages. what you see is what you get from them:

grimmspeed:
Air/Oil Separator - WRX/STi/LGT/FXT - GrimmSpeed

crawford:
Separator

iag:
http://www.iagperformance.com/SearchResults.asp?Search=iag+aos&Submit=

perrin:
http://perrinperformance.com/i-14908570-air-oil-separator-for-wrx-sti.html

moroso:
Air-Oil Separators

element:
Element Competition Catch Can

the first four products all share one thing in common; they all return oil to the crankcase, which is a huge improvement over delivering that crap into the intake via the pcv. back in prehistoric times ('04-5), we only had one choice; which catch can to buy. if youve ever emptied a catch can after a hard track session, youve seen what comes out of it. it is a disgusting froth of broth and vapor product whipped up by your spinning crank. if i poured you out a cup of it and said to you, i want you to pour this back into your engine, you would protest, tell me i was nuts and to fuck off. that's pretty smart.

some of these aos systems look better than others. beauty is in the eye of the beholder. for the sake of argument (and whether it is true or not) lets say they all six work equally well. of course they don't but lets say they do for now. i'll let you guys slug it out in the thread.

let's also say, of all six, the moroso and element units are the ugliest units in the pile. it's actually a fair statement to make re: the element unit. the one thing that the moroso and element units will let you do that the other four don't is, empty that cup of splooge somewhere else. you decide where, but once you look at it, you won't pour it back. the only downside is, you can't plumb it and forget it. you can't be lazy. you have to empty it. the element unit is designed for high hp/boost engines. it may not be the most appropriate unit for less ambitious applications.

when i started the thread, the search feature gave me a list of other aos threads on aos systems:

http://www.iwsti.com/forums/vendor-announcements-project-buildups/269959-iag-billet-aos.html

http://www.iwsti.com/forums/2-5-liter-litre-factory-motor/224508-grimmspeed-aos-vs-crawford-aos-review-2.html

http://www.iwsti.com/forums/2-5-liter-litre-factory-motor/180583-crawford-air-oil-separator-top-10-questions-answered.html

http://www.iwsti.com/forums/vendor-announcements-project-buildups/269959-iag-billet-aos.html


it won't be lost on anyone that element is a sponsor of mine. as usual, i'll probably continue to edit this first post. if i'm missing a manufacturer, post something and i'll add it. also as usual, i'll try to sit back and let others pick up the discussion. i know that all of these manufactures have fan bases here on iwsti. i expect you to defend your favorite product and i hope you do. i know you will. respect to you all.
 
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Info is great to have in one spot. The MOROSO does not return the oil back. For the subarus it is a ball valve on the bottom for emptying catch cans via tubes or just a cup. You could yes try and run it back to the crank case and leave the valve open but that is not how it was designed to function

These have worked flawlessly at what they are meant to do in all of our testing
 

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I ran the Peterson catch can for 5 years (which I assume is what Element Tuning rebranded) and I have had no regrets switching to the IAG AOS when they released it.

1. The IAG AOS had 3 ports so it relieves crankcase pressure a lot more efficiently.

2. The turbid, milky stuff I empited from the Peterson catch can was predominantly during winter time whereas in the summer it was more clear oil consistency which can be attributed to the climate change. Keep in mind that the catch can is not heated so that is why it is milky in the winter. The IAG AOS is heated with coolant so it will retain the clear oil consistency year round and that is the stuff that goes back into the crankcase. The heated coolant perfusion design of the IAG AOS is the most uniform throughout the can and superior to Crawford and Perrin.

3. Furthermore, since the IAG AOS actively empties, the oil will not sit around in the can itself to even have a chance to condense into that frothy substance.

4. The Peterson catch can had a chance to fill up with oil on hard cornering G's on the track and this sequestered the oil into the catch can and deprives your motor of oil. The IAG AOS will return that oil quickly back into the crankcase.

5. The Peterson catch can left oily residues in the adjacent structures which initally escaped from the breather filter. Not only was it an eye sore but could potentially pose a fire hazard. Moreover, the fumes emitted from the oil sitting in the catch can was nauseating for my passengers even though I was acclimated to it.
 

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'do right & fear no one"
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Discussion Starter #4
The MOROSO does not return the oil back.
correction made. thanks, js. i blame any confusion on moroso for not having a better and more detailed description of the unit on their product page.
 

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I've had the ugly Moroso's on my DD for about two years with no regrets (other than getting to the drain valves with my big hands).
Everything said by everyone above seems accurate to me. I think they all get the job done, it just comes down to personal preference: some people like Subaru's, others Chevy's. Both do the job, just with different style.
 

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Another misconception that often follows these devices (and there are boatloads of them out there) is that the 'goo', 'peanut butter', 'froth', or whatever you want to call it is bad. It is not. It is a byproduct of temperature variations, oil, combustion and so on. It has been around for well over 100 years and has never once been determined to cause and negative issues with oiling. In fact, it is found on nearly every surface on the inside of an engine. It will be found less on components that remain mostly hot (rods, pistons, etc.) and more on those that are more directly in contact with ambient air temps (PCV lines, oil fill tube, valve covers, etc.).

Personally, I am a fan of a well designed A/O separator as they keep more oil where it should be, in the sump. I've seen far too many times can setups that are done improperly; filling in 20 minutes of track time, or worse, overflowing and causing a fire. Just about once a month I get a 'why is my catch can filling up' e-mail. A well designed A/S separator will work well for 99.6% of the applications out there and require zero attention after installation.

Of course the top priority of any of these devices should be not allowing oily vapors into the intake tract.
 

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I can only speak about my own experiences with the moroso unit, used now with 4 track weekends and multiple auto crosses. With daily driving I will empty it with every oil change, I will get about a 1/4 inch of light oil mixed with some water. In the winter it will be more milky with what I assume is more water mixed in. I will get the same amount out each track day that I get after 3000 regular driving miles, but it is more like regular oil with no water mixed in. I personally would not pour that back into the engine and I like that I can monitor how much oil is being caught as a way to potentially catch a problem early. The downside is that it is a pain to empty, and that if something catastrophic happened, it will probably fill quick, but I would imagine that if that scenario happened, full catch cans would be the least of my worries. I can also attest that my inter cooler is free of any oil residue.
 

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'do right & fear no one"
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Discussion Starter #9 (Edited)
I ran the Peterson catch can for 5 years (which I assume is what Element Tuning rebranded) and I have had no regrets switching to the IAG AOS when they released it.

1. The IAG AOS had 3 ports so it relieves crankcase pressure a lot more efficiently.

2. The turbid, milky stuff I empited from the Peterson catch can was predominantly during winter time whereas in the summer it was more clear oil consistency which can be attributed to the climate change. Keep in mind that the catch can is not heated so that is why it is milky in the winter. The IAG AOS is heated with coolant so it will retain the clear oil consistency year round and that is the stuff that goes back into the crankcase. The heated coolant perfusion design of the IAG AOS is the most uniform throughout the can and superior to Crawford and Perrin.

3. Furthermore, since the IAG AOS actively empties, the oil will not sit around in the can itself to even have a chance to condense into that frothy substance.

4. The Peterson catch can had a chance to fill up with oil on hard cornering G's on the track and this sequestered the oil into the catch can and deprives your motor of oil. The IAG AOS will return that oil quickly back into the crankcase.

5. The Peterson catch can left oily residues in the adjacent structures which initally escaped from the breather filter. Not only was it an eye sore but could potentially pose a fire hazard.
it is not the same can as the peterson you had, user. peterson manufactures it to phil's specs. this from the horses mouth:

"It is not a Peterson Breather Can. We have changed the design 3 times over the years but our can is 3.5" in diameter for maximum capacity, has -12 and -10 breather ports. Everything about our can is custom manufactured for Element Tuning and we are even the only company that makes the 3.5" band clamp as that didn't even exist. Because the spun tops and custom clamps are not mass produced for any other applications, it drives the cost to where it is currently. "

...which is about twice the cost of a peterson breather can. you get what you pay for in this case.
 

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We've always used and recommend the Crawford units. I even run and old pre-liquid heated unit on our shop 05. They offered to replace it when the heated units came out, but it works very well and this particular car, sees very few cold short drives. I do also prefer vacuum based products; if it's done right it will help evacuate blowby gasses more efficiently, cause oil to drop out of suspension better, an not stink or leave residue how a VTA filter will. I like products that are simple, work, and you never have to think about after installing them.

All that being said, in the last year there are some new products on the market that may work as well as the Crawford, but we've not had an opportunity to test them ourselves. Some designs look well thought out. As I said before a well designed unit should work well on nearly all application.
 

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Glad there is new AOS thread. The old one is too cluttered.

I've been eyeballing AOS systems for a while now, don't burn any noticeable oil, but have a light coating in the intercooler. Now with stg 2 and eventual protune, I'd like one before I go lapping next season.

I'm looking for a system that eliminates the return to the intake, and am not fond of having to empty a can, or drain into the crankcase(prefer this potion over the two though).

I read the IAG system can vent to atmosphere under the car and drain to crankcase. Would it be possible to plug that in downstream in the cat back so that the vapor exits the exhaust?

Finally if it's vta and eliminates the pic system, could a simple home made can and mesh system work for what I'm thinking?
 

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Glad there is new AOS thread. The old one is too cluttered.

I've been eyeballing AOS systems for a while now, don't burn any noticeable oil, but have a light coating in the intercooler. Now with stg 2 and eventual protune, I'd like one before I go lapping next season.

I'm looking for a system that eliminates the return to the intake, and am not fond of having to empty a can, or drain into the crankcase(prefer this potion over the two though).

I read the IAG system can vent to atmosphere under the car and drain to crankcase. Would it be possible to plug that in downstream in the cat back so that the vapor exits the exhaust?

Finally if it's vta and eliminates the pic system, could a simple home made can and mesh system work for what I'm thinking?
The VTA of IAG's system has absolutely no smell from my personal experience. If you are staunchly worried about how much you are hurting the environment then it might not be the system for you. Most of us don't care since we run catless downpipes anyway.
 

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The VTA of IAG's system has absolutely no smell from my personal experience. If you are staunchly worried about how much you are hurting the environment then it might not be the system for you. Most of us don't care since we run catless downpipes anyway.
That's all I need to hear. I'm not worried about the environment more than any other sti owner. Was just worried about the smell and if it would bother my wife.

Just looking for the best bang for your buck VTA oil return AOS that works
 

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For those of you concerned with venting to atmosphere or smelling the oil vapors, we will be releasing our V2 AOS in a "Street Series" variety. The vent to atmosphere version will now be referred to as "Comp Series". In approximately 45 days we also plan to release a "Race Series" that will feature 100% AN fittings for use in motorsport applications. Stay tuned ;)

 

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For those of you concerned with venting to atmosphere or smelling the oil vapors, we will be releasing our V2 AOS in a "Street Series" variety. The vent to atmosphere version will now be referred to as "Comp Series". In approximately 45 days we also plan to release a "Race Series" that will feature 100% AN fittings for use in motorsport applications. Stay tuned ;)
I am really leaning toward the IAG AOS in the next couple weeks since ive heard so much about it. Im very curious about that vent to atmosphere line though. Are there any issues with this for those of us running EWG? Any more info on the "street series" compared to the current IAG AOS?
 

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One disappointment I see in all the AOS on the market is the lack of vacuum maintained. I have the moroso unit, but re-plumbed to keep the vacuum from the intake manifold while running out of boost. Most high performance engines run some type of crankcase vacuum system for a reason, better ring performance, which is a serious issue. I see no advantage other than price and ease of installation for ignoring this. For a DD, I also like the idea of monitoring the contents of the cans as an indicator of my rings health.
 

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I am really leaning toward the IAG AOS in the next couple weeks since ive heard so much about it. Im very curious about that vent to atmosphere line though. Are there any issues with this for those of us running EWG? Any more info on the "street series" compared to the current IAG AOS?
We have sold over a 100 AOS that are vent to atmosphere and I would say at least half of those cars are equipped with EWG. We have not heard of a single complaint or issue. In fact, with the exception of one unique application, which we are working with the customer on determining if the install was done correctly, we have not seen anyone even have oil coming out of the vent hose.

One disappointment I see in all the AOS on the market is the lack of vacuum maintained. I have the moroso unit, but re-plumbed to keep the vacuum from the intake manifold while running out of boost. Most high performance engines run some type of crankcase vacuum system for a reason, better ring performance, which is a serious issue. I see no advantage other than price and ease of installation for ignoring this. For a DD, I also like the idea of monitoring the contents of the cans as an indicator of my rings health.
The "Street Series" AOS is designed to address those concerns. While we still strongly recommend that most applications use the "Comp Series" that vents to atmosphere, we do understand that there is a group of Subaru owners that want to still maintain a vacuum on their crank case system. The "SS" AOS will include a new PCV and customers will have the option of installing with or without. Note dual return ports to inlet and PCV in the end of the top that will connect to a vacuum source. I hope that helps.
 

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Dragging this back from the dead... and wondering if there is a more comprehensive discussion or comparison, especially since KillerB entered the game not that long ago. Testing of any vs others?

Are some street versions really requiring a retune? Which ones can be used that do not affect a new car warranty?
 
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