I'm still struggling with notable oil coming into the airbox during autocross or track events. It seems to be coming in from the BOV, from what I can tell.

This happens during autocross events, or track days.

Here's what I have:
Engine: street port, downpipe, catback, airbox, SMIC, PowerFC, etc. Running about at the limit of stock injectors. Engine and turbos rebuilt about 25k miles / 15 years ago.
Suspension: Ohlins coilovers, r-compounds for autocross, stick streets for track.

Variations in venting system, with only small variations in results:

Started with a small hole vent in the oil filler cap - made a mess on the underside of the hood.

Added a catch can, fed from the top of the top of the oil filler cap with a fairly small hose. The can was vented with a hose pointing down. Would fill some, oiled the airbox.

Added a Stainless, baffled oil fill neck. Not much difference. Has 2 1/4 npt bungs.

Removed the vent tube during a smog day. Back to stock system. Not much difference.

Re-installed catch can. Into the can with a 3/8 hose from the filler neck, with the return going back to the piping near the filler neck which goes into the turbo. Basically adding a non-vented catch can in the vent line. The catch can does catch oil, as well as the airbox.

Do I need a different or upgraded system?

Some suggestions I've read or heard:
Vent the catch can. (or not)
Larger catch can. (that big one from Summit with the filter vent looks good)
Plug the PCV valve (line).
Larger hose to the catch can. With 1/4 NPT fittings I can get nipples for 1/2" line.
Enjoy the longer life of the rotors with the bonus oil injection. (LOL!)
New turbos. (hmm....)

Thanks!

 

Disconnect and plug the PCV line from the oil fill neck to the UIM. Disconnect the other line on your oil fill neck and connect it to the outlet of your oil catch can. Then connect the inlet of your oil catch can to the oil fill neck barb that had the hose that is now connected to the outlet of your oil catch can (or conversely you can plumb the outlet directly to the primary turbo). Basically you are putting the oil catch catch can on the hose that connects the primary turbo to the oil fill neck. The primary turbo is pulling vacuum and is sucking the oil from the oil fill neck which is getting into your airbox via the BOV. It's also probably getting into your IC. See: Remove PCV Valve but use rubber fuel hose as silicone is not oil resistant.

 

I'm not in FD guy and it sounds like Tom has a pretty good idea as to what's happening, it sounds like the oils coming up the filler neck, IR Performance has a group buy currently for an upgraded oil fill neck which will not allow oil up the neck because of internal "baffling" and makes running a catch can easier(double bungs welded to the neck below the baffle)you could shoot Ihor(IR Performance) a PM they're probably busy moving into the new shop but he's very good at responding to communications
GL

 

+1 on the IRP oil neck. They have two versions, one with two -6 AN ports for stock plumbing with the PCV and one with one -10 AN port. They are quality parts.

 

Thanks Tom,

Other that deleting the PCV valve, the Rob Robinette page is pretty much how I have my current can hooked up. And it does catch oil!

My neck is an older stainless one, sounds similar to the IRP one but with 1/4 NPT bungs instead of the larger AN bungs.

Why does deleting the PCV help?

 

Ok, see that now. You might be still be getting blowby if you are not emptying the catch can often enough and the vacuum could be pulling oil from the catch can into the primary turbo inlet. I routinely emptied my catch can after each run (at least a pint) and have since upgraded to a larger and baffled catch can. Some recommend venting the catch can. This decreases the vacuum somewhat as it's pulling from both the oil fill neck and the vent which reduces the oil it's pulling from the neck (but also the crankcase gases). You can search the debate on vented vs. non-vented.

It only helps when the PCV is bad and since it's somewhat redundant, it's recommended to just delete it. When the intake is in vacuum vice under boost, the UIM will pull crankcase gasses from the oil neck via the PCV. When the intake is in boost, the PCV closes otherwise intake charge would be forced through the PCV into the oil fill neck. Since the primary turbo inlet is always pulling vacuum, it's better to just pull the crankcase vapor from there which is why they eventually nixed the PCV on the '95s.

 

^^ this. I used to have catastrophic amounts of oily residue blowing out of my BOV all over the engine bay when doing track days with high-g right turns (causing the oil to creep up the fill neck and be pulled through the intake tract). It was so bad my car would literally be smoking out the edges of the hood as I came off the track. Doing the '95 style PCV conversion, using a baffled fill neck, and installing a catch can between the neck and the other vacuum source as described above fixed all my problems for good. You may want to remove and drain your I/C. Some folks on here will recommend running a quart of oil low but I have found I don't need to do that with my setup.

 

All of the advice here has been good. No PCV needed, put catch can in-between oil fill neck and primary turbo line. If the catch can fills though you'll pump oil into your turbos and that's likely why it's coming out of your BOV.

I've run with no PCV, baffled fill neck, and vented catch can. I still had to run at the 1/2 mark on the dipstick to keep from regularly filling the catch can (still a small amount). My newest move has been to move to a different oil pan in hopes of making dealing with the catch can easier.

 

Great input from all above!

Sounds like I'm on the right track, with the biggest opportunity being to plug the PCV line.

My can isn't filling, but got about 2/3 full at our last autocross, which had about a 600+ degree right hand turn. (yes, a double loop around an island - only a little extreme)

Perhaps a fancier catch can is in order, a larger capacity one with baffling.
Is something like the Radium Engineering can a good solution? Universal Competition Catch Can

Smokey The Talon: I'll be interested in how the new pan works out! What did you get?

 

That catch can looks pretty sweet. SPENDY TOO!

I'm using the baconsports pan. Honestly the reason I think it'll help is that I can run it at the 1/2 mark on the dipstick just like before but when I do there's still a full 4 quarts in the sump so I don't have to worry about running low. First test should come later this month if I can get the car together in time.

 

I just got a package from Radium last week everything was packaged extremely well, all the products I have purchased are top-notch that catch can is on my must-have list!