True Air-Oil Separator or working Catch Can?

[SleeperScoob]

I have been doing a bit of research on AOSs and catch cans, but I've seen mixed reviews on both.

 

I'm fully aware that the GS AOS or any "oil cap" style AOS does little to nothing as far as separating air and oil, haha.

 

Of course, I've looked at the Crawford AOS which provides more of a catch can style filtration system that seems as though it would do its job to some extent, but I've now seen posts and pictures about these clogging up quickly and are in turn rendered useless. If I'm going to drop $300 to stop oil from shooting into my intake tract, it had better damn work well.

 

I honestly would like to see some sort of PCV routing that either dumps into a catch can that I can empty, or just straight to the ground. (Do not get into an environmentalist argument with me about dumping gas/oil vapors onto the ground, that's not what I'm here for.)

 

If anyone has any good, factual information on which systems and routings work best for keeping the PCV dump out of my intake, burning up in my exhaust, clogging my cat, and giving me that burned oil smell, that would be awesome.

 

Thanks in advance, guys!

[whitrzac]

Catch can you have to empty. Just having it drain on the ground would coat the underside of your car with oil.

 

The grimspeed AOS works well enough to be usefull. I use to have a light coating of oil in the intake/intercooler. It has since gone away.

 

I'm stg3 with a bnr18g. If your going to go larger, buy a better one, or use a catch can with the grimspeed unit.

[SleeperScoob]

If the underside gets coated with oil, I only see that as rust preventative. Haha

 

Interesting idea, I'll look into that.

[Max Capacity]

What kind of HP are you making ? How much boost ?

 

I have a AOS on my wagon that mounts on the oil file tube. I won't bother doing it on my Spec B.

[Nightmaresmk]

Three main AOS setups i like. IAG which i personally have on my car. Perrin a small but very nice setup and the original crawford which is very well documented.

Grimmspeed has a known issue with their aos and catch cans are not good for daily drivers or our engines in general as we can put a lot of oil in the catch can starving the motor.

[mondtster]

Has anyone tried one of the OE BMW oil separators? Seems like it could be an inexpensive alternative to the aftermarket kits, and one that wouldn't require occasional draining like a catch can would.

[covertrussian]

Has anyone tried one of the OE BMW oil separators? Seems like it could be an inexpensive alternative to the aftermarket kits, and one that wouldn't require occasional draining like a catch can would.

 

Got any images/diagrams of how they work?

 

Here is what mine looks like on an SR20:

http://i160.photobucket.com/albums/t188/covertrussian/Sentra%20SE-L/Blow%20By/Oil%20Catch%20Can%20Reroute/CIMG1910.jpg~original

 

As per FSM diagram it has levels that should prevent blow by from going up from crancase, but the effectiveness is still not the best stock, esp with turbo powers, thus I still had oil in my Intercooler. This diagram is from an NA SR20 where the breather is attached to the intake couple inches from throttle body. The stock turbo version of the SR20 sends the breather to the turbo inlet, which allows everything (piping & IC) to also can get coated by oil. Unfortunately with all turbo motors, you only vacuum source at full throttle is the turbo inlet.

http://i160.photobucket.com/albums/t188/covertrussian/Sentra%20SE-L/Blow%20By/Oil%20Catch%20Can%20Reroute/Blow-BySystem.jpg~original

[mondtster]

Got any images/diagrams of how they work?

 

They work on the same principle as the Perrin and other similar separators do. I don't have any pictures, but the internet is full of them if you just google "BMW air/oil separator."

 

I've been planning on trying one out, haven't gotten around to doing it yet though. I suspect it will work fine, it just won't be as elegant or expensive as the aftermarket performance versions.

 

If the BMW oil separator doesn't work I'll probably look into some of the OE options being used on modern diesel applications. A ton of money is spent on researching ways to separate the oil from the crankcase ventillation air on diesels, might as well use some of their research to help us.

 

EDIT: Here is a link for one photo of one of the BMW oil separator setups someone used on their race car. The only problem with it is that I believe they have it hooked up backwards, but you'll at least get an idea of what it looks like.

 

http://vsetrack.com/track_reports/2010/bmw_motorsport_oil_separator/bmw_motorsport_oil_separator.htm

[rhino6303]

I have a Perrin and it works very well. The main reason I chose Perrin over IAG or Crawford is because the Perrin unit still keeps the PCV in the system.

[SleeperScoob]

Interesting stuff, thank you guys.

 

Max, I'm still on the VF40 @ ~17psi. I plan to a give JmP a blown VF46 to do a hybrid build for an E85 setup to keep it quick but conservative. Quick spool and good low end torque is what I'm after.

 

Covertrussian, thank you for that diagram of PCV operation, it helped me better understand how it works. Though, I'm assuming that's for an N/A application.

 

The BMW AOS idea is cool, I'd like to see that done on a turbo EJ for sure.

[mondtster]

Covertrussian, thank you for that diagram of PCV operation, it helped me better understand how it works. Though, I'm assuming that's for an N/A application.

 

Turbo or not, the PCV principle is the same. Remember, these engines are designed to be running lightly loaded 99% of the time, spending most of their life with manifold pressures less than atmospheric. Under those conditions the PCV system will work the same regardless of whether there is a turbo on the engine or not.

 

Diesels are another story, but we aren't discussing them.

[Nightmaresmk]

I have the IAG with the PVC system intact as well.

[SleeperScoob]

Lightly loaded 99% of the time for you, maybe

Lol

Interesting.

 

I'm going to do some more research. Thank you for the resources, everyone!

[quick4dr]

iag COMP, no more pvc, my oil consumption reduced dramatically compared to my grimmspeed set up. The rest of my oil was going out my turbo seals. thats remedied by a 1.5xtr in a box waiting for install

[luchadorjose]

catch cans are not good for daily drivers or our engines in general as we can put a lot of oil in the catch can starving the motor.

 

I disagree with this logic. Any oil that makes it into the catch cans is oil that would have been sucked into the intake and burned during engine operation. You won't starve the engine any different than a stock setup, but at least you're getting a cleaner running motor and less chance of knock due to oil air/fuel mix. I personally have a dual catch can system and prefer it over an AOS because it gives me feedback as to how much blowby I'm getting during operation. Any turbo subaru owner should be checking their oil regularly anyway, and checking the level in the catch cans adds maybe ten seconds onto that check.

 

I'm not saying catch cans > AOS, I'm just saying that the only difference between a well performing catch can setup and a well performing AOS setup is that the AOS setup is something you don't have to check regularly, but it also doesn't tell you anything about how your car is running

[covertrussian]

Covertrussian, thank you for that diagram of PCV operation, it helped me better understand how it works. Though, I'm assuming that's for an N/A application.

 

The BMW AOS idea is cool, I'd like to see that done on a turbo EJ for sure.

 

Here is an 05 LGT diagram, concept is same as for even NA motors

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/Engine/General/PCV%20Valve/LGTPCVFunction.png~original

[tocinoman25]

Saikou michi...i have his dual OCC setup...unfortunately I didnt have the patience to to unstall myself but Mark at APM Tuned was a fan of it and installed per crawfords instructions...so its and AOS catch can haha... he said best of both worlds

 

http://www.saikoumichi.com/

 

Cant beat if for the price...i will do my firs5 oil change after my road trip and see what it collected.

[covertrussian]

EDIT: Here is a link for one photo of one of the BMW oil separator setups someone used on their race car. The only problem with it is that I believe they have it hooked up backwards, but you'll at least get an idea of what it looks like.

 

http://vsetrack.com/track_reports/2010/bmw_motorsport_oil_separator/bmw_motorsport_oil_separator.htm

 

Thanks, I luckily found a picture of the cutaway and holy crap it's stupid simple

http://i1095.photobucket.com/albums/i467/mach-schnell/M5OS.jpg

[762x39]

If the underside gets coated with oil, I only see that as rust preventative. Haha

 

Interesting idea, I'll look into that.

 

I was just going to type this when I saw that you already posted it!

[mondtster]

Thanks, I luckily found a picture of the cutaway and holy crap it's stupid simple

 

Indeed they are simple, and I believe that is all that is really going to be required. Most of the true oil separators I've looked at operate off a similar principle, the air gets spun inside the unit and the oil separates and goes to the bottom. My current thought is that I can install one of these back by the right strut tower then tie the oil drain in with the turbo drain and just route the crankcase vent hoses where they need to go.

 

If the BMW separator doesn't work out I'll probably look into a Mann ProVent separator, which is more expensive than the $20 BMW option but it is still cheaper (and probably better) than the aftermarket performance options being offered.

 

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

[Nightmaresmk]

Checking your oil is basic. Just saying that people that autocross etc have thrown enough oil out to cause engine failure.

[Streetlegal]

I disagree with this logic. Any oil that makes it into the catch cans is oil that would have been sucked into the intake and burned during engine operation. You won't starve the engine any different than a stock setup, but at least you're getting a cleaner running motor and less chance of knock due to oil air/fuel mix. I personally have a dual catch can system and prefer it over an AOS because it gives me feedback as to how much blowby I'm getting during operation. Any turbo subaru owner should be checking their oil regularly anyway, and checking the level in the catch cans adds maybe ten seconds onto that check.

 

I'm not saying catch cans > AOS, I'm just saying that the only difference between a well performing catch can setup and a well performing AOS setup is that the AOS setup is something you don't have to check regularly, but it also doesn't tell you anything about how your car is running

 

What dual catch can system do you have?

[luchadorjose]

Just a modified Ebay special, welded in a pair of baffles and stuffed them with copper wool

[covertrussian]

Indeed they are simple, and I believe that is all that is really going to be required. Most of the true oil separators I've looked at operate off a similar principle, the air gets spun inside the unit and the oil separates and goes to the bottom. My current thought is that I can install one of these back by the right strut tower then tie the oil drain in with the turbo drain and just route the crankcase vent hoses where they need to go.

 

If the BMW separator doesn't work out I'll probably look into a Mann ProVent separator, which is more expensive than the $20 BMW option but it is still cheaper (and probably better) than the aftermarket performance options being offered.

 

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

 

 

I've been thinking about this a ton and thinking of a way to avoid having a setup that you have to drain (which is what even the BMW one has to do).

 

I think the best solution for daily would be a gravity based inline filter baffle. Similar to the one I posted for the Nissan, basically a self maintaining system that should be sufficient enough for daily driving.

[mondtster]

I've been thinking about this a ton and thinking of a way to avoid having a setup that you have to drain (which is what even the BMW one has to do).

 

I think you're misunderstanding the idea behind the separator. The bottom port gets plumbed back to the oil pan, which makes the system completely self supporting and maintenance free.

 

The return location doesn't seem to be terribly important. Every one of them I've seen however, has the drain above the oil level. I'm not certain that this is really that important but it is just the way they are.

 

My thought is that you could possibly tie into the turbo oil drain line to get the oil back into the pan without cutting and welding much.