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Thread: need some imput on catch can configuration

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    Better than that "other" place Not Verified Feedback Score 2 (100%) x2xtreme360's Avatar
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    need some imput on catch can configuration

    I'm thinking of simply getting rid of the stock setup. I've been using compressor oil separators as catch cans, but it's really counterproductive as the hoses are everywhere.

    I'm thinking of replacing the PCV valve with a simple barbed fitting and running the hose from the front valve cover and rear valve cover into a single inlet on a cheap ebay catch can and putting a filter on the outlet.

    I figure it's a little more economical than dumping the blow by onto the pavement. I know the ebay catch cans normally do a really bad job of filtering out the oil from the intake on re-entry, but it wouldn't matter if it weren't being directed back into the engine.

    Something like this:



    Anyone else run the PCV system this way?

    Vacuum reduction, Powdercoated misc, cruise relocate, Evo9 BOV, Custom catch cans, Russell fuel filter, SS braided fuel lines, High flow fuel loop, Autogage fuel gauge, Catless DP, DNP Y-pipe, Fuel pump hotwire.

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    Better than that "other" place Not Verified Feedback Score 2 (100%) x2xtreme360's Avatar
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    Quote Originally Posted by steve68 View Post
    You'll end up with your oil contaminated with fuel and water.

    Steve
    Care to elaborate on that?

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    Better than that "other" place Not Verified Feedback Score 2 (100%) x2xtreme360's Avatar
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    Quote Originally Posted by steve68 View Post
    Because it screws up your PCV system. Best thing to do is just fix it, seeing that only broken motors need catch cans.

    Steve
    How exactly does it screw up the PCV system? The stock system is set up exactly the same except it goes back into the intake. The only thing I'm changing is not directing it back into the motor.

    And catch cans aren't for broken motors. Every engine has blow by. I don't have a lot of it, but that nasty gunk accumulates over time and I don't want that.

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    What you would be doing there is basically running open breathers. Just adding small filters to the crankcase would achieve the same thing. The stock system actively evacuates the crankcase of blowby, your system or open breathers pretty much just prevents the crankcase from being pressurized. The oil would become more contaminated by blowby than with the stock system because excess blowby will not be vacuumed out of the crankcase. What's your setup now? I also run a air compressor filter inline and it isn't bulky at all:


    I guess most engines don't need a catch can, but if you want to keep oil and other junk in the blowby out of your intake tract, you'll want something there. Many oems have something in the pcv system to do this, our cars do not.

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    Better than that "other" place Not Verified Feedback Score 2 (100%) x2xtreme360's Avatar
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    ^^And I know what you're saying. I've debated that with people for a long time. Some say the vacuum doesn't matter... I've always thought it did. I simply run two of those separators in line for the front and rear valve covers, but it makes for a lot of bulk if you try to mount the canisters like I did. I don't let mine just hang, like the one in your picture.

    Also, I'm confused by that picture above.... where did you get that valve cover?
    Last edited by x2xtreme360; 11-03-2010 at 01:18 AM.

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    seize the carpe! Feedback Score 0 Lithium's Avatar
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    Sure that would work just fine, I would suggest you invest into an oil/air separator or if your smart you could modify that catch can to work like one. As for blow by, I don't care what steve says with enough pressure ANY engine will have it.

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    Quote Originally Posted by x2xtreme360 View Post
    ^^And I know what you're saying. I've debated that with people for a long time. Some say the vacuum doesn't matter... I've always thought it did. I simply run two of those separators in line for the front and rear valve covers, but it makes for a lot of bulk if you try to mount the canisters like I did. I don't let mine just hang, like the one in your picture.

    Also, I'm confused by that picture above.... where did you get that valve cover?
    Vacuum can definitely matter. Basically, combustion and normal engine operation produces a cloud of blowby in the crankcase, pulling that out and replacing it with fresh air will keep your engine cleaner. Good constant crankcase vacuum (more than the stock pcv system produces) actually can produce a nice little bit of horsepower. That being said, I don't think you will lose any power running open breathers over the stock system. You'll just may be smelling crankcase fumes more and you will want to change the oil more frequently. Plenty people run open breathers, but that's mostly because it's so simple. I could see how two mounted compressor filters could be bulky. In the past, I was thinking about running something like you have above, but after some research, I decided the stock pcv system was pretty well thought out (besides the whole dirtying of the intake tract thing). I have a jdm mivec engine in my car and the valve covers are a little bit different. I was just posting the pic to illustrate the general idea.

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    seize the carpe! Feedback Score 0 Lithium's Avatar
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    Ive had two Professionally built 500+HP subaru 2.5 motors that Had blow by above 24PSI. A blanket statement like "a motor that had blow by is bad" doesn't apply. In a perfect world no motor should have blow by but every motor has a small amount.

    Quote Originally Posted by steve68 View Post
    Have you ever had a look inside the valve cover and examined the screens inside?

    Anyway one of my previous motors (about 3 back now) had no blowby at all, not until it got thrashed a bit and the filler cap started leaking, Only a tiny bit of oil got into the intake pipe. Of course I knew it was broken, just 2 ringlands on one piston and one on another.
    It makes more sense to fix it, at least in my own case.
    Good motors don't have blowby, not unless it's got forged pistons and been built loose enough so that when it gets hot the piston doesn't scuff, then get stuck and throw out a rod. I've done that too. That one didn't have any blowby either but it was too tight.
    That valve cover is the same as mine.

    Steve

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    seize the carpe! Feedback Score 0 Lithium's Avatar
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    Quote Originally Posted by steve68 View Post
    Subarus are totally different, because they're aluminium block/sleeved, different piston to bore clearance. Probably wasn't done right.

    Steve
    Do you have to be such a jackass in everyone of your posts? I guess I didn't realize I was talking to Jesus via 3SGTO. The motors were built by Cosworth, I would like to see you call and tell them they have no idea what their doing. The 6G72 is sleeved too genius, what does the block material have anything to do with blow bye? Please educate me.

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    Better than that "other" place Not Verified Feedback Score 2 (100%) x2xtreme360's Avatar
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    Interesting read Steve... and it makes sense to me that the PCV side doesn't need to go to a catch can as it's only functioning at low levels of blowby and it's right before the air enters the cylinders.

    Now, I love the idea of boring out the breather ports on the valve covers, although ours are already fairly large to begin with. I do see that in that article, they recommend (if legal) to simply run the breather hose to a catch can and vent to atmosphere. I can see how this would be benefical because the only purpose of the breather is to allow air to be "pushed" out under boost and then it gets "sucked" in under vacuum due to the PCV valve being open at idle and cruise conditions.

    The only thing I completely forgot about is that if I were to do that, I would be allowing a small amount of unmetered air in the engine through the PCV side if the breather were vented. I wonder if this would cause negative effects.

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