AOS or Catch Can? I'm seeing conflicting and contradictory answers.....

Alin

Diehard Car Enthusiast!
I know there are about 10 different previously created threads on this crap because I just read them all. However, there are so many different responses that contradict each other BOTH in terms of which system to use. An AOS or a catch can. Now, a vented catch can or a recirculated one?

Gahhhhh!!!! Some people say you don't even need one.... So we can make this ultimate thread on AOS and catch cans and then sticky it! Let's begin:

Air Oil Separator, catch can, or both? If a catch can, recirculating or a vented? If AOS, which brand? I want to come to ONE, best conclusion!



daaaaaaaaang, four pages and we are still discussing/wondering? well let me put the nail in the coffin on this one. With everything that everyone has been saying in reference to "well it didnt come from the factory like that for a reason" yes, you are right. The way cars are built and constructed they have to meet emission requirements ALL across the board and build them ALL the same (thats how an assembly line works to maximize profits). well we cant "dump" anything into the atmosphere because gore swears it tears up the ozone layer. That's why, stock, these cars come with all the fancy performance restricting parts that if you change them (expecially in california) you run the risk of failing emissions testing. either mechanical (cats, O2 sensors, changing the tune) or visual (evap system). all those things keep everything environmentally friendly but kills performance. so when it comes to catch cans/venturis/aos WHATEVER those are in reference to the evaporative emission control system (evap). the way the stock system works is that is routes all of the oil precipitants or moisture from the block and heads back into the intake tract for it to burn. Some of it is valved and some of it is not(problem). the purpose of the valves is to prevent positive boost pressure being pushed into the motor thus deterring the chance of positive crankcase pressure. so far no advantages right? as time goes on you will start seeing things like this: View attachment 4566 in some of the evap lines due to moisture in the oil or things like this: View attachment 4567 and View attachment 4572 with the vapors building up or actual oil being pushed back through the intake which causes oil consumption and making the intercooler less efficient. it also coats sensors and creates buildup on the injectors and valves.

so whats the relief? well one of the worst things out there i have seen in the GS AOS. why? because this:http://forums.nasioc.com/forums/showthread.php?t=2228499 It sounds good the way GS sells it but common! its all marketing and from a mechanical standpoint its a horrible design. I cant believe how something like that can cost so much and THEN be ineffective.

option 2: the crawford AOS. Again on paper it sounds good, but my OMG its expensive and do you really need coolant running through it? not only that moisture builds up in the oil and it really doesnt get "caught" or separated and the crawford AOS STILL runs it back into the intake so for me, no thanks.

the BEST option, #3: this: http://www.elementtuning.com/images/products/Element Competition Catch Can.jpg or this: https://www.himni-racing.com/images/catch can rx8.jpg this is what bip power hondas and v8's use. yes, you might have to deal with possible fumes and extra maintenance but that is the sacrifice when it comes to modifying cars and going into more higher performance.

if your catch can system is working right you'll see things like this: View attachment 4568 and this: View attachment 4569

now do you really want that crap being recirc into your expensive built motor? or just avoiding a rebuild all together? the crawford markets their product well when it comes to "low maintenance" and looking good in theory but to pay triple for that? or even build your own catch can for less? no thanks. catch cans is a simple yet good design that has been used for YEARS thats PROVEN and they come in all sizes and designs and have the possibility to be cheap, expensive, customizable, WHATEVER...

and to the person who that something about lateral g's and what not; garbage. there is a reason why the oil pan and valve covers are baffled and there are oil galleys positioned how they are. how do you think baja trucks, and drag cars deal with oil starvation? autox cars run the lowest risk and even still there are better oil pans that we can purchase if you want peace of mind. as long as the oil pump can still suck up oil, its all good.


and lastly, thanks JJ for putting this topic on facebook. I wouldnt have been able to give my input if it wasnt for that...

Just a thought hear... Not sure you would want it to go back into the system at all. In some cases like running E85 in the winter time, there is an awful lot of moisture that winds up as blowby and the catch cans condense and separate it well enough.

You definitely don't want this water finding it's way back into the engine. I pull two cups of water form my catch cans every two to three weeks.



Here are the top brand I keep seeing over and over again:
Grimmspeed
Crawford
Morose
IXIZ
Prova

http://scoobytuner.com/products/?vApplicationID=25&sfID1=356&sfID2=365

Catch cans:

http://www.jmfabrications.com/store/products/Deluxe-Oil-Catchcan.html
http://www.allstarperformance.com/product.htm?prod=25

Then, there is this:

https://www.mann-hummel.com/fileadmin/user_upload/service/catalogues/pdf/ProVent_en_2013.pdf

And last, but not least, a cheap alternative to an AOS.

http://www.speedelement.com/index.p...oduct_id=2980&option=com_virtuemart&Itemid=38
So, what do I go with?! :angry:I really want to listen to everyone, but all these different answers are driving me insane. Same with the other forums. Everyone is just contradicting themselves on which system is best and why. :lol: :banghead: :rambo:
 

IGOTASTi

System Operator
Staff member
We would like to know the same thing to be honest.

:idontgetit:
 

Alin

Diehard Car Enthusiast!

IGOTASTi

System Operator
Staff member
Nope.

Was talked out of it.
 

IGOTASTi

System Operator
Staff member
Will have to look for it.
 

ZachTTLM

New member
I have heard many of the different arguments as well and it really makes things hard for the consumers IMO. I know my word is not gospel but I direct customers to the AOS systems. These keep the oil out of the intake system with low maintenance versus the oil catch cans which need emptied often and when they are not emptied they fill up and end up dumping more oil into the system at one point than what happens with the normal blow by issues.
 

Spamby

Meat Product Toy
I've got the moroso and I believe it separates oil, moisture and air, catches the goo and let's the air return.
 

Grinder34

Track Monkey
Personally, I opted for the IXIZ AOS. I like it because its totally maintenance free. I routed the "return" to, well, the ground.

If you're going to go with an AOS, dont do the Grimmspeed one. Its "fine" for daily driven cars, but it really does a poor job at actually separating, and there are confirmed cases of high-G issues. Meaning if you ever track the car, or do some spirited canyon runs, you can actually mess things up. Go for the Crawford, IXIZ, or something more...complex.

I got mine off of Fuji, back in the day, and I think even he thought it was a good product (I mean, he bought it!). He was selling because he ran into issues at really high boost levels (IIRC ~30psi), but I never plan on getting that high, so I think I'll be alright.

From my reading the evap system on our cars is controversial. Theres no single great option. Catch Cans are definitely preferred if you're willing to check them regularly, but I wanted a more hands-off approach.
 

Alter3go

New member
AOS for life. I don't think anything more robust is needed Unless you build your motor because you do want to protect your investment. Not saying you wouldn't want to on your subie. You shouldn't be pulling near as much gunk into your engine as a built motor. Also I check mine every oil changes as well as the intercooler and turbo and haven't seen anything alarming. The AOS is know the get blockage and a milky substance forms in the tubes which normally means u have them cut/placed incorrectly. If that's the case squeeze the tubes and let hang to drip out. Did I mentions it's a five minute install
 

Alin

Diehard Car Enthusiast!
Still waiting on input from [MENTION=9]HolyCrapItsFast[/MENTION] . :tup:

Was doing some reading on IWSTI and so many different people say they went with A, B ,C ,D, or E. That each of those brands is best because of this and that. One person says Brand A is the best and then comes 20 others saying that it isn't.....

So what do I need to look at in order to get the best item that suites my car's needs?
 
there are many different options and they cater to different people's wants. I like the catch cans because oil saturated air goes straight to the can(s) and air goes where air is supposed to go. I dont want anything else going into the intake tract other than pure air and that is how i see it. Like ive mentioned before, the evap system is designed to cut down on emissions so that is the design that virtually every car on the road uses. With that being said, catch cans are rec. by me because they are cheap and the most effective. the more crank and head pressures you are working with when increasing power the more potential blowby you will have. I dont like the AOS systems because they are good for stock setups or mild street setups but pretty much end there. not only that they are expensive as hell. So it comes down to preference. pick what you so desire.
 

Alin

Diehard Car Enthusiast!
there are many different options and they cater to different people's wants. I like the catch cans because oil saturated air goes straight to the can(s) and air goes where air is supposed to go. I dont want anything else going into the intake tract other than pure air and that is how i see it. Like ive mentioned before, the evap system is designed to cut down on emissions so that is the design that virtually every car on the road uses. With that being said, catch cans are rec. by me because they are cheap and the most effective. the more crank and head pressures you are working with when increasing power the more potential blowby you will have. I dont like the AOS systems because they are good for stock setups or mild street setups but pretty much end there. not only that they are expensive as hell. So it comes down to preference. pick what you so desire.
Ok, that's what [MENTION=9]HolyCrapItsFast[/MENTION] suggested as well. I just wanted a more in depth explanation. Link me to something that's similar to your set up. I've linked up in the first post what I have found so far. :tup: :ty:
 

Spamby

Meat Product Toy
I couldn't say either way. I guess both have their advantages and disadvantages.
My head spun when I was researching, as well. In the end, Fuji recommended the Moroso setup and the rest is history. No issues. No oil in my IC. And I dump them every oil change and watch the milkshake and water pour out. Lotsa water due to E85 and short driving.
 
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Ok, that's what @HolyCrapItsFast suggested as well. I just wanted a more in depth explanation. Link me to something that's similar to your set up. I've linked up in the first post what I have found so far. :tup: :ty:

A catch can is a very simple design. All it is generally is an aluminum container of some sort that is either enclosed or outfitted with a breather filter. I bought one off of ebay that was about 30 dollars and modified it to have 3 ports (one for each head and one for the crankcase). It has a breather filter on top and a level indicator. does the job perfectly
 
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