Crawford Air-Oil Separator Problem: Lots of Oil in Intake
 

Yesterday I did a bit of disassembly of my HKS supercharger and found such a wonderful picture.

That looks exactly like what I wanted to avoid by installing a Crawford AOS instead of Cusco AOS (a real catch can) which I had previously. It was for the PCV line only but drainable.

Knowing that people recommend that for boosted applications, I installed a Boomba check-valve on the PCV line, as you can see – the red one in the middle, to prevent pressure from the manifold to enter into the can and then the engine.

The result looks far from satisfying. I started to ask questions (probably a bit too late – after spending $400 on this device, but still): how the caught oil actually gets back to the engine? Simple answer is gravity which should do the job. However, the PCV valve is a check valve itself and it prevents anything from entering back into the block. This was tested empirically (and resulted in tasting some engine oil in my mouth): I wasn’t able to blow any air into the engine block via the PCV hose (the one on the left, the stock one) but you can easily suck it out from there.

So, I just don't understand how the oil could escape the can other than via the right ventilation line – the uppermost of the 4 holes on the can, which goes directly to the intake right after the intake box and then all this goes to the SC, intercooler and right to the throttle body... You can see on the pics how it looks (and I don’t even want to imagine how much of this dirty oil is in the intercooler).

I'd be happy to hear that I'm wrong and this AOS is a great magical device but looks like I need a catch can which keeps the caught oil in it and better vent the gases to the atmosphere to make sure nothing goes to the intake... Suggestions and advices welcome! Thanks for reading.

Tha Crawford AOS will not work on a boosted application without a check valve. And even then, it's dicey. That whole can is a terribly bad effing design.

If you join the 2 crankcase lines into the same cavity and apply boost...

Either way, you are correct about transferring oil back thru the PCV, it will not work. If you want to keep your PCV system intact and have a working catch can, you need 2, or if you want a "maintenance-free" option, the AVO can drains to a modified oil cap, and back to the engine that way. I did not opt for that and have no idea if it works as advertised.

Thanks for reply! I'm more than happy to do maintenance! I'd also love to get a good easy-to-install vent-to-atmosphere option and the only car-specific that I found is AVO dual tank system. However, from 1 or 2 pics that I found, it looks like those 2 cans are still interconnected by a hose and only one of them is venting to the atmosphere which contradicts to what you are saying (and I tend to agree with) - better to have the 2 lines and 2 cavities separately.


What setup are you running/can recommend as a replacement for me?

I could make you one of our dual can VTA set ups from our turbo kit if it's something that might work for you?

http://i742.photobucket.com/albums/x...ps476b91be.jpg

As I say, I haven't used it, but I wasn't talking about a VTA setup. I believe the non-VTA can is 2 separate chambers in the same container. Just like having a dual catch can, just having both independent cans in the same housing. Again, not 100% as I haven't used it. I just assumed you were after a low-or-zero maintenance system given your choice of the Crawford system.

I personally use the RacerX can, which is the same way; 2 completely independent catch cans in the same housing. I setup drain lines with ball valves so I can drain them from under the car. It comes with those now.

My setup works great, but if I were to do it again, ... Well actually I wouldn't change anything. The maintenance is virtually zero. Just draining little dribbles out of the can every once in a while... Intake is clean.

Ah, that said, examining the Crawford can further, it occurs to me that it (should) work as advertised it you replace the original PCV valve into the block with a plain old straight-through NPT fitting, thereby relocating the PCV check valve to the snout of the can. That way, it would actually drain to the block, and the check valve at the "snout" (where you have it right now) makes the valve at the block redundant. That is, of course, provided that its "swirl pot" design actually separates any oil at all. Given that I doubt that is the case, I bet you'd still end up with oil in the intake... But it may be worth a try.

Looks and sounds awesome! PMed.

Have you checked your intercooler for possible oil contamination

Not yet, since I'm sure that it is contaminated as there was oil before and after it. I will clean it and the entire intake path once I get a new catch can.

Current setting you have will be pushing boost into engine crankcase via intake manifold, this AOS is designed for NA cars and needs to be modifed to be run for boosted applications, otherwise you pressurize the can. The mod basically turns it into a a poor mans dual catch can type setup. You really need two independent cans to do it properly, that being said i'm running this AOS on my turbo setup. I blocked the short hose that goes from can to intake manifold and replaced the check valve on the back of the block with a regular barb fitting(that check valve only opens under vacuum). Its not ideal but it works.

*Edited looks like they put a one way valve ( the red piece) to stop what i mentioned from happening, maybe that failed?

http://i.imgur.com/GImwiNA.jpg?1

If you are after a VTA can, I have a brand new Full Blown VTA catch can that I fit then removed a few days later during my turbo build ( its never been run). I had to switch to a recirculated system in order to get my build engineered. Willing to let it got for $100 US + shipping ( im in aus, shipping wouldn't be more than 30 US) let me know sir

Yes, I also came to the conclusion that this thing is for NA only, at least it is harmless in this case. However, Crawford claims that this AOS if OK for boosted applications either, that they run it on their race car and it works fine even without the check-valve! Sounds either like magic or like BS because the key question: "Where the caught oil goes, via which tube?" Remains unanswered.


The red thing is Boomba check valve which I added myself (thanks for FT-86 SpeedFactory who bought it specially for me and included into shipment of other parts). I had to cut about 1 cm of the outlet tube of the AOS to fit it into the short hose between the can and the intake manifold). It works fine - requires very little effort to pass air into right direction and blocks attempts to blow anything into the opposite direction (from the manifold).


Thanks for the offer - I'll consider it. However, I want a dual catch can for both lines, like the one which MAPerformance offers. Alternatively I'm thinking about Radium dual cans.

I run dual Radiums in my car Love them!!!!!
Drivers side vented to Atmosphere
Passenger side factory hook up
Absolutely zero oiling issues

WATCHING

So, after some investigation I came to the conclusion that I need a decent vent-to-atmosphere catch can. Ideally dual catch can so that to be able to define from which port all this oil is coming from.

The best solution which I found so far is @MAPerformance dual can:
http://i742.photobucket.com/albums/x...ps476b91be.jpg

However, it seems that its mounting points are exactly the same as those which are used to mount AT harness in my AT GT86, so it not AT-compatible unfortunately, at least not with the standard mounting bracket. If someone could confirm/dismiss this assumption - that would be really helpful.

The next candidate is @AVOturboworld dual breather tank:

http://www.ft86speedfactory.com/medi...breather-6.jpg

However, its desing puzzles me. Why acually they made two cans interconnected one after another? As the result the first one is used just an intermediary which mixes air from both breathing lines and then air goes to the 2nd one with the filter. Also, I don't understand whether it's possible to drain the cans without dismounting (although it's easy and not a problem). Strange construction with unclear purpose but very comfortable mounting and looks like workable solution.

The third candidate is @Element Tuning Competition Catch Can System:

http://www.elementtuning.com/images/...%20Can%20b.jpg
http://elementtuning.com/store/#!/El...ategory=439244

Which is a single can with simple and understandable desing but I'm not sure about FRS/BRZ-specific mounting...

No one is ideal but still I need to choose one. What would be you recommendation guys? Any other suggestions are appreciated!

Add W1 catch can i what i use. Its baffled, can be used as a closed loop or vent to atmosphere. Add another $10 in hoses and clamps, and your in business. I use this on the driver side from the pcv valve to intake, works very well and catches alot of oil.

http://www.ebay.com/itm/ADD-W1-Black...3D141097569813