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Old 06-21-2018, 12:58 PM   #1
c4lvinnn
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Default Catch Can Routing Confirmation

Quite a few ways to route this, but anyone confirm if this is correct catch can config or at least the most "popular?" Dont mind the crude drawing I had to do in paint lol. Just wanted to double check some things. Intake is capped off.


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Old 06-21-2018, 01:19 PM   #2
~The_Duke~
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That's about right, except for the Drain.

All of the AOS diagrams have the drain T'd into the "Deleted PCV on crank case" So that it blows oil out of the vent into the can, then when you're off the throttle and there is a vacuum on this line it literally sucks the oil out of the AOS\catchcan and back into the crankcase.

Instead of having the vent to atmosphere you can run that back around to the turbo inlet if you wanted to be exactly correct per the instructions.
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Old 06-21-2018, 01:24 PM   #3
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Quote:
Originally Posted by ~The_Duke~ View Post
That's about right, except for the Drain.

All of the AOS diagrams have the drain T'd into the "Deleted PCV on crank case" So that it blows oil out of the vent into the can, then when you're off the throttle and there is a vacuum on this line it literally sucks the oil out of the AOS\catchcan and back into the crankcase.

Instead of having the vent to atmosphere you can run that back around to the turbo inlet if you wanted to be exactly correct per the instructions.
This will just be run as a traditional catch tank and not recirculated back into the crankcase like an AOS as this is not baffled (temporary until I get the IAG AOS) in which it will be drained back in per instructions.
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Old 06-21-2018, 01:34 PM   #4
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So... I tried doing something like this...

If you are doing any sort of motorsports, track day, mountain run, etc. I would discourage using a catch can period on a Subaru.

Here's why...

So apparently if you are changing directions a lot, causing a lot of G-Force that oil is going to slush right into the head in which the force is pushing it toward. That's then going to get blown right into the catch can... The can is then going to fill up almost instantly.

I filled up a small can in 1 60 second autox run.

If you are vent to atmosphere you're going to cause a huge oil spill and possibly a fire depending on where you have your can mounted.

If its vented to the turbo inlet... *queue james bond theme* huge oil smoke fest. (this is what happened to me, I was referred to as the mosquito fogger all weekend). I am still trying to get all the oil out of my damn exhaust... Went through a healthy amount of oil as well...

My adventure started when my PCV valve took a crap on me and caused a vacuum leak \ oil blow through fest because of the bum PCV. This bought gave me a heart attack...

I would wait till you can install install the IAG as long as your PCV valve is working right.
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Old 06-21-2018, 02:34 PM   #5
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Quote:
Originally Posted by c4lvinnn View Post
Quite a few ways to route this, but anyone confirm if this is correct catch can config or at least the most "popular?" Dont mind the crude drawing I had to do in paint lol. Just wanted to double check some things. Intake is capped off.


Your design eliminates the low-load PCV which I would only recommend for a track car as it will cause the catch can to fill more quickly (not dramatically faster, mind you... unless you screwed something up). That said, the design is sound if you drain regularly.

Also, your design should use an effective baffle system within the catch can, use fairly long hoses, and the can itself should be positioned high on the firewall, if you can manage it. All of these details will lessen the amount of oil that gets blown through the filter and all over your engine bay. An even better solution is to run the filter at the end of a hose down a rocker panel - very easy to do with a small grommet on the firewall (into the wiper motor area).

Quote:
Originally Posted by ~The_Duke~ View Post
So apparently if you are changing directions a lot, causing a lot of G-Force that oil is going to slush right into the head in which the force is pushing it toward. That's then going to get blown right into the catch can... The can is then going to fill up almost instantly.
This should only be true if you tap into the wrong head port (the balance ports). The baffled fresh air ports should not do this.

Quote:
...temporary until I get the IAG AOS...
I highly recommend trying this system a while with some basic baffles you make yourself (assuming you can open the can)... then decide if you want to shell out $300 to essentially have the same thing.

Last edited by mrsaturn7085; 06-21-2018 at 02:41 PM.
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Old 06-21-2018, 02:37 PM   #6
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This should only be true if you tap into the wrong head port (the balance ports). The baffled fresh air ports should not do this.
Right, the balance port is as is (red in the pic) and is not part of the catch can system.

Except that I have a forged motor so I expect blowby being trapped in the can.
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Old 06-21-2018, 02:39 PM   #7
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Quote:
Originally Posted by mrsaturn7085 View Post
This should only be true if you tap into the wrong head port (the balance ports). The baffled fresh air ports should not do this.
The ports that I have used the ones that IAG \ Crawford have noted in their install instructions. So I would assume that is not the case.

If they were truly baffled fresh air ports then there wouldn't be a need for a catch can or AOS system...

Do you have a picture for reference?
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Old 06-21-2018, 02:42 PM   #8
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Quote:
Originally Posted by ~The_Duke~ View Post
The ports that I have used the ones that IAG \ Crawford have noted in their install instructions. So I would assume that is not the case.

If they were truly baffled fresh air ports then there wouldn't be a need for a catch can or AOS system...

Do you have a picture for reference?
Don't have a pic, but on the back of the crankcase there is a baffle cover and the valve covers have internal baffling.

They are there but not entirely efficient at doing its job hence why even stock, thesr motors produce larger amounts of blowby than other turbo 4 cylinder cars.
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Old 06-21-2018, 02:55 PM   #9
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Originally Posted by c4lvinnn View Post
They are there but not entirely efficient at doing its job hence why even stock, thesr motors produce larger amounts of blowby than other turbo 4 cylinder cars.
Right and that inefficient mitigation of the blow by made even worse by the oil slush effects of g-force changes...

I know 2 different cars that overpowered the Crawford AOS by filling the sucker up in a single autox run... Hoosiers = lots of force throwing the oil to the heads = more oil than there is supposed to be coming through the crankcase vents -> catch can fills up.
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Old 06-21-2018, 06:03 PM   #10
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Quote:
Originally Posted by mrsaturn7085 View Post
Your design eliminates the low-load PCV which I would only recommend for a track car as it will cause the catch can to fill more quickly (not dramatically faster, mind you... unless you screwed something up). That said, the design is sound if you drain regularly.

Also, your design should use an effective baffle system within the catch can, use fairly long hoses, and the can itself should be positioned high on the firewall, if you can manage it. All of these details will lessen the amount of oil that gets blown through the filter and all over your engine bay. An even better solution is to run the filter at the end of a hose down a rocker panel - very easy to do with a small grommet on the firewall (into the wiper motor area).



This should only be true if you tap into the wrong head port (the balance ports). The baffled fresh air ports should not do this.



I highly recommend trying this system a while with some basic baffles you make yourself (assuming you can open the can)... then decide if you want to shell out $300 to essentially have the same thing.
Unfortunately it's a solid unit that's not serviceable and I couldn't see any filter media in there, but I did see some chambers for the vapor/"swirl pot" area. I've already tried a Perrin AOS, which was very undersized for my set up so I was constantly puking oil out of the ports. and eventually had to VTA it because it overflowed into the intake tract which is absolutely nothing I ever want to encounter (again), so VTA eliminates that altogether. It's a forged motor so also no big deal with deleting the PCV. Just makes it simpler in the end. I also daily drive the car so basically maintenance-wise on the catch can basically every time I stop for gas to check it etc is going to get very annoying, so I'm going to try this until my break in period is over and go recirculated IAG AOS.
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Old 06-21-2018, 07:49 PM   #11
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Quote:
Originally Posted by ~The_Duke~ View Post
The ports that I have used the ones that IAG \ Crawford have noted in their install instructions. So I would assume that is not the case.

If they were truly baffled fresh air ports then there wouldn't be a need for a catch can or AOS system...

Do you have a picture for reference?
Reference images are available in every single Subaru FSM, Mechanism and Function sec.

The PCV (fresh air) ports are internally baffled - the unbaffled ports are balance ports. Balance ports are most common on motors with a large distance between heads, such as a boxer motor. PCV ports being baffled is common to literally every motor made since the closed venting requirement laws were enacted... so literally decades. Look at the underside of any rocker cover on any motor made in the last 20 years or so.

This is why I think it's funny that people think Subaru just 'forgot' to put an air-oil-separation system... it's in there, and it works quite well. What do you think that labyrinthian plate is behind the clutch? That's also part of the separation system.

The purpose of a catch can is to collect condensed oil vapor when the (legally required) sealed system is changed to a vented system by the end user rather than just venting it freely. For what it's worth, venting freely works GREAT as well, but it's certainly not the most environmentally friendly solution, and it is completely illegal in many racing regulations.

The purpose of an AOS (for most people) is to sell you a catch can for 5 times more money. Any catch can that promotes the condensation of oil vapor can technically be considered an air-oil separator and even an empty 1 liter soda bottle causes the vapor to travel some distance, giving the oil particles more time to fall out of suspension. See where I'm going here? Catch cans and AOS are one in the same. The product name 'air-oil separators' originated from people buying air compressor water traps (also called air-oil separators) and installing them inline between motors and catch cans to enhance oil separation. Honda guys did a lot of this in the early-90's.

For the small minority that have outpaced the OEM PCV and oil separation system, the purpose of the AOS (i.e. catch can with genuine oil separation features) is to enhance the venting and oil separation capacity of the motor. Raise your redline? You almost certainly need one. Raise your boost? You *might* need one. Run an excessively loose motor? Find a better builder next time (also, you might need an AOS).

A drain-back system is a feature of either a catch can or AOS - it does not define either. To me, this is a band-aid for poor decisions - if you are losing so much oil you need to recirculate the lost oil to the motor for what you're using it for, you're either running a racing motor on the street or you have worn parts or terrible clearances.

Given a normal ~0.5-1.0 qt. drop between changes, a drain-back system also encourages you to be lazy with oil changes. This is particularly bad news on a turbocharged Subaru as the geometry requires extra fuel for charge cooling under boost. Richer charges = faster oil dilution and diluted oil = ineffective lubrication. If there's one thing that Subaru owners enjoy more than complaining about bearing failures in EJ motors it would probably be neglecting normal maintenance schedules. Draw your own conclusions there.

As a side note, any time you're racing, you're running pig rich the entire time. This is why an oil change after a track day is always a GREAT idea. Second side note - if you're one of the few who think you need to run racing oils on the street (Motul 300V, etc.) you've also introduced time as a big factor in oil change scheduling. Racing oils only last a few months in a motor before they break down.

Quote:
Originally Posted by c4lvinnn View Post
Don't have a pic, but on the back of the crankcase there is a baffle cover and the valve covers have internal baffling.

They are there but not entirely efficient at doing its job hence why even stock, thesr motors produce larger amounts of blowby than other turbo 4 cylinder cars.
You nailed the info about the baffling, but you've been drinking the Kool-Aid on the second part. If you're burning more than 1 qt. between changes (and your motor isn't built too loose, running 2+ bar of boost, spinning 12k RPM, etc.), your motor is worn out... sorry. If you're burning about a quart or a little less, you're doing about as well as every turbocharged 4 banger made since about 1980 once they hit 40k miles or so.

There is nothing magical about Subaru motors - they're subject to the same emissions laws as everyone else.

Now, what 'The Duke' is likely seeing is an oil pan that does not have effective baffling for the driving he is doing (the Hoosier comment changed my thinking here - it's hard to tell how serious someone is about AutoX until you start talking tires).

The PCV ports are baffled to promote the condensation of oil vapor... not to stop liquid oil. In his case, improved pan baffling with one-way doors will be a BIG help. You don't need to go and buy a $1000 pan - most of those are overkill (do you *really* think you need to jack up your entire car by the oil pan? Yeah, me neither). Search out some baffling designs online and find a good welder - you could probably fab up about 20 designs using the OEM pan and sheet metal before the cost added up to the price of aftermarket cast or welded pans.

Now you mention someone 'overpowered' an AOS... well, no... they didn't. Sounds like they had a stock oil pan. Maybe you can comment on this?

Last edited by mrsaturn7085; 06-21-2018 at 07:54 PM.
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Old 06-22-2018, 01:37 AM   #12
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I learned the hard way that inadequate line size off the heads combined into a T going to one VTA filter is not large enough to handle long sweeping turns at high speeds. VTA or or catch can, make sure you use large enough hose to handle a the possible oil loss. This was with only the high load head lines..... The low load pcv was connected as normal.
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Old 06-22-2018, 08:48 PM   #13
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I got it all set up. Instead of the Y for the front most valve cover ports, I used a T meeting in the middle and routed to the top port of the can with equal length lines at all 3 junctions. The original PCV location crankcase breather needed another 90 straight off the port to clear the compressor turbo inlet, but other than those two changes it's set up. Did a few hard pulls and drove to/from work (~80 miles total) and drained it when I got home which was less than .5 ounce. Will keep an eye on it. My hesitation is with the T junction is restricting flow vs a Y but for crankcase I don't think it matters (I may be overthinking this one because OEM uses a T). May run a line and put the breather on the line on top breather port so it doesn't make a mess in the engine bay and just route it somewhere towards the ground or something.
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