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Old 11-30-2012, 05:15 PM   #1
Scooby Newbie
Member#: 107228
Join Date: Feb 2006
Chapter/Region: RMIC
Location: CO
2006 WRX Wagon

Default Another catch can install (w/pics)

I had 2 teeny compressed air filters set up as catch cans before and decided to do it better. It was also set up wrong... one was catching absolutely nothing.

Stuff used:
Silicone vacuum hose, 10 13 16 and a little bit of 19mm
2 3/4-1/2 hose barb reducers
2 5/8-1/2 hose barb reducers (pain to find)
2 1/2-1/4NPT hose barb adapters
2 1/2-1/4NPT 90 degree hose barb adapters
1 1/4NPT 90 degree male-female fitting
1 3/8 hose barb 90 degree fitting
2 catch cans (the ones Mach V sells)
many hose clamps

First, I broke the short little factory PCV hose that connects under the throttle body. In with the 10mm hose. I had to reuse the factory spring clamp because there's no way to get a better one under there.

19mm hose here, coming off the block right under the turbo outlet where the PCV tee used to sit. Again, had to reuse the weird factory hose clamp.

19mm gets reduced to 13 mm in the center here then runs to the PCV catch can. To the left is the hose from the PCV valve to the throttle body. On the right is the hose from the PCV tee back to the intake tube.

Here's the relocated PCV tee. Annoyingly it has 3 different hose fitting sizes. 19mm on the left (used to go to block), 16mm on the right (gets reduced to 13mm on the way to the intake tube) and 10mm from the PCV valve. I used fuel injection hose clamps on the PCV line just to be sure, since it sees boost.

Here it is all finished. The front can is for the PCV, the rear for the valve cover breather system. 13 mm hose from the valve cover breather tube to the can, and 13mm from the can upsized to 16mm before it goes back into the intake tube.

Now, about those cans... I got them because they aren't terribly expensive and supposedly are internally baffled. They do indeed have what appears to be a several layer screen separating the upper and lower chambers.

But guess what... both fittings are tiny and go into the upper chamber. The screen can't do anything if its not intercepting the flow of gunk. So I drilled and tapped both of them making the fittings larger (1/4 NPT) and relocated the inlet to the lower chamber. The aluminum is thick enough for this to work. The cans don't come apart but do have a drain plug on the bottom. I will probably be taking them out and just dumping them when it comes time. Luckily the valve cover one doesn't fill up fast.

They do indeed work, catching a fair amount of water along with oil. In retrospect, some super cheap Ebay cans with DIY baffling would have been just as good.

Before someone says 'Crawford', I did look at those. They seem like an ideal solution for a built car. But that setup removes the PCV system. Sure any crankcase pressure can get still get out, but there can't be much vacuum scavenging of the crankcase going on. On my street car I'd rather have the PCV system working. I hope these don't freeze up.

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Last edited by iberian_wolf; 12-01-2012 at 06:34 PM.
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Old 11-30-2012, 05:21 PM   #2
Scooby Specialist
Member#: 277487
Join Date: Mar 2011
Chapter/Region: NWIC
Location: Bozeman, MT and Lakewood, WA
2006 CGM WRX Limited
6sp, 18G, Phatron tuned


Nice pics. I bought a Simota catch can a couple of months ago and ditched it due to their custom fitting. It's some weird super coarse thread and I could only get replacement fittings through them. Also the fittings are alumninum and SUPER thin. I sheared one, leaving the threaded part still intact and took me like 10 minutes to back it out with a small flat head screwdriver.

I hadn't thought about drilling them out to a common size. Thanks for the idea.
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Old 11-30-2012, 05:27 PM   #3
Scooby Newbie
Member#: 107228
Join Date: Feb 2006
Chapter/Region: RMIC
Location: CO
2006 WRX Wagon


Should anyone attempt this, the top fitting needs to be drilled and tapped at a bit of an angle or your tap will hit a tube that's in the center of the can.

Also compressed air and strategic rinsing should get the metal shavings out.

Bonus install on my Ranger. Hyperactive PCV system makes quite an oily mess in the intake manifold.

Last edited by iberian_wolf; 11-30-2012 at 05:43 PM.
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Old 12-01-2012, 03:20 AM   #4
Scooby Specialist
Member#: 190502
Join Date: Sep 2008
Chapter/Region: International
Location: Sydney, Australia

Not many people get the routing of hoses right when doing a dual catch can setup, good to see you have nailed it. I have a custom Saikou Michi dual can setup going on mine with the same routing you have used, the Saikou cans are dual stage 3 (biggest size he makes), internally baffled, and he has made the hose connections 19mm on one can and 13mm on the other for me as requested.

Here is the order sheet, mine is RHD and my battery is under the passenger seat so the cans will be going where the battery was.

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