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Old 03-23-2004, 04:54 PM   #1
Scooby Newbie
Member#: 33566
Join Date: Mar 2003
Chapter/Region: International
Location: Aberdeen, Scotland
Lightbulb Forester FXT Oil Catch Can Install

UPDATE 6/16/2004 - See second post at bottom

After reading and pondering much about the emissions and PCV system on the 2.5 turbo I went ahead and built a prototype oil catch can system.

I've seen others installs, and the cans look really pretty, but I'm not going to drop $100+ for something that may not work that well. So I went ahead with my own prototype build and here it is in picture form. Maybe this will give a good idea over time of what type of system would be most effective.

First off, I’ve seen a lot of install and it seems that many people really don’t understand how the PCV system works and therefore introduced external, unmetered air into the intake as well as rendering the one-way PCV valve’s vacuum effect useless. Not only does this lean out the intake a bit but more importantly it raises crankcase pressures decreasing piston ring seal and increasing combustion blowby. The stock system is built with evaporative emissions in mind and is not a true “performance” system. If the 2.5 was built for performance in mind the valve covers would be sealed and a mechanical vacuum pump would be installed to evacuate the crankcase to atmosphere through a catch can of some variety. Obviously this is not really emissions or spill friendly so the stock system reintroduces these into the air intake pre-turbo in hopes of burning the nasties. Since I didn’t really want to mess with the emissions or engineering I went ahead and placed my system in-line with the current system with no additional vents.

Now for the system: It consists of two catch cans, one for the valve cover vents and one for the PCV system. It is easily removable if need be as no stock parts were permanently modified. I did choose to mount the cans using the DRL bracket and thus had to do away with the DRLs. The system could be mounted elsewhere but I found this to be the most convenient. I constructed it out of PVC plastic and though I’ll give the dimensions for the pieces I used this is really a self-engineering project. If it works a custom dual chambered aluminum tank would be cool, but would require a bit more fabricating. Materials list and pictures follow below.


Unit - Description
2 - 2.0” center connectors
4 - 2.0” O.D. x 1.5" Thread Diameter threaded inserts
4 - 1.5” threaded caps
1 - silicone rtv
1 - Aluminum screening
1 - Coarse steel wool
4 - ½” NPT brass hose barbs
1 - ½” brass hose barb connector
2 - 3” hose clamps
1 - 7 ft. of ½” fuel or heater hose.
1 Teflon Tape

Pic 1. – Here are the cans laying down. Flow goes in the horizontal barbs at the bottom and flows through the screening and out the top. The bottom caps are not in the picture here. Construction is pretty obvious with the materials listed above. Two sections of aluminum screen were pressed into the center of the can using the threaded inserts and a block of wood. Make sure you use silicone while building to seal everything up. The screen will make the inserts press fit pretty tight. Make sure to add a little steel wool on top of the first screen pressed in so you can sandwich it with the second threaded insert and screen from the other side.

Pic 2. – Looking into the bottom of the cans. A bottom cap is there for size. Teflon tape was used to seal the bottoms and the brass hose barbs after drilling and tapping the PVC.

Pic 3. – Close up of the screening. It looks solid but is really only a 1/8th in thick and presents very little restriction.

Pic 4. – Catch cans installed in place of the DRLs. I used the bracket and some hose clamps running around the bracket to secure the cans. It’s a tight fit and not as easy as I’d hoped to remove the bottoms of the cans for inspection and cleaning.

Pic 5. – Here is the PCV junction. I simply removed the current PCV hose from the intake replaced it with the ½” line from the catch can and used the ½” hose connector to extend the PCV line to the catch can.

Pic 6. – Here is a picture of the overall install of the sytem. The hoses I used were ½” fuel line and as such turned out to be pretty bulky. The install would look better if the hoses were smaller.

Any questions feel free to ask. Also note the "Peaty" intercooler screen . I commute right next to the colorado river and the bugs can get pretty obnoxious sometimes. I'm thinking of adding some screen in front of the radiator too.
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Last edited by SubaruCO; 06-16-2004 at 03:23 PM.
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Old 03-23-2004, 05:56 PM   #2
Scooby Newbie
Member#: 42249
Join Date: Aug 2003

Very nice! Look forward to your updates on how much oil this is catching.

Doing some work on my Maxima the other weekend, even the NA motors collect quite a bit of oil in 30k of driving. My intake manifold had several small pools of clean oil.
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Old 03-23-2004, 08:18 PM   #3
Techno Sapien
Member#: 449
Join Date: Oct 1999
Chapter/Region: MWSOC
Location: Lawrence, KS
2016 BRZ Limited
Ice Silver Metallic


Nice setup, check your PM
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Old 06-16-2004, 02:04 PM   #4
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Member#: 33566
Join Date: Mar 2003
Chapter/Region: International
Location: Aberdeen, Scotland

Here's an update at the next convienent oil change. Total milage on the cans is about 3500 miles. The cap on the left is the valve cover vents and the one on the right is the crankcase PCV vent. Both had moisture in them with a slight oil-looking discoloration, but it appeared that there was little to no actual oil residue in either can. Either I don't drive hard enough (possibly) or different engines perform differently due to atmospheric conditions, driving habits etc. Sorry about the blurred photo, I forgot to set the camera to closeup mode.

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Old 06-16-2004, 03:27 PM   #5
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Join Date: Jun 1999
Location: Naperville, IL
2005 Legacy GT
98 BMW 540i LS2/T56


How much space is there between the bottom of the horizontal fitting and the bottom of the canister?

In other words, how much oil can the canister hold?
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Old 06-16-2004, 05:37 PM   #6
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Chapter/Region: International
Location: Aberdeen, Scotland

Not all that much...probably about .5 cup per can (1/8 quart, 118 cc's). I don't think that I came anywhere close to filling that up with oily water in 3500 miles. Also I believe that the water evaporated off as the cans get pretty hot sitting close to the turbo.
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Old 07-01-2004, 06:17 PM   #7
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Join Date: Feb 2003
Chapter/Region: MWSOC
Location: Dayton, OH
2004 Impreza STi


I have heard that if you don't put something in the cans, you won't turn up any real sludge. Some folks are using gauze tape or cotton balls. But I am not really sure with the way you have it setup if that would make a difference. Maybe something else to test though.

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