legacycentral bbs

Yep, coating the inside of the IC with oil reduces cooling efficiency big time! One of the main reasons I plan on installing a catch can on my vehicle.

ive decided to run it open. ie, one tube to the ground. i dont want any junk in my fresh motor.

I think I'm just going to connect the main crankcase vent to the PCV valve and put a pair of breather filters on my EJ25D heads when I get them on. Living in Minnesota lets me get away with things like that, or the complete lack of my evap system

I would advise strongly against putting breather filters on your valve covers.
The reason being you want to actually scavenge that oil vapor out and create a little bit of vacuum inside the crankcase. Not to mention you're going to make one heck of a mess with the filters breathing oil all over the side of your engine and strut towers.
Even a road draft tube, such as the one juice91si said he is going to use creates some negative pressure at the end of the hose to pull out the vapors. For simplicity sake, this is the way to go as it's cheap, easy, and effective. Over-the-road semi's still use this system. Mack, International, Peterbilt, Kenworth can't be wrong!

A proper catch can is one that uses a vacuum source, a one-way valve from the plenum going to the top of a well-designed catch can that filters oil out of it before it enters the engine. Also when you create some vacuum in the crankcase it not only helps scavenge all that nasty oil vapor, it actually helps seat the rings.


Just my $.02, ymmv.

Its actually not messy. A friend of mine uses them and has had them on for about two years, and there is very little oil on his vavle covers, or anywhere else.


I'm probably not going to use the breather filters, and am well aware of the advantages of putting vacuum on the crankcase. Also, the engine isn't new so my rings do not need to be seated.

I'll cross that bridge when I come to it.

n2x4 wrote:Could the HP gain come from the fact that oil isn't being sent through the intake and into the engine? Burning the oil would lower your octane rating and IC efficiency. Maybe enough for 2HP?

No because they tested the car with open atmosphere breathers and that gave a HP loss compared to the stock PCV system.

You want vacuum in your crankcase, as much of it as possible. When the back side of your piston is under vacuum it makes it easier for the piston to move up and down. Imagine if while there is pressure pushing the piston down, there is simultaneously pressure pushing UP against it. THAT is what happens when you get too much pressure in your crankcase and then you get oil shooting out of your valve covers and other places. I had this problem on my Legacy and it actually started on fire because the oil shot out the bottom of the valve covers right onto the hot turbo manifold. So the MP's and the fire department showed up and it was bad. I checked compression and I was leaking pretty bad on cylinder #4 but all the cylinders were pretty worn out at 160,000 miles. Cylinder #4 was letting all the boost get around the rings and the PCV couldn't handle it so oil was puking out of everywhere.
I also had a problem on my Jetta where I drove it thru a lake and a bunch of water got into the crankcase. Yeah that blew a rod because there was too much pressure but that probably wouldn't have been avoided by anything other than draining the water out LOL.

So anyhoo some of these Corvette and V8 guys will actually run electric vacuum pumps on the crankcase to make more vacuum. It gives the motor more power and makes it run better. It just makes sense right?
Ever tried to close a door in a room with all the windows closed and then tried to do the same thing with the windows open? The door slams shut doesn't it? Well this happens on a very small scale in your engine every time a piston moves up and down.

Learning is fun

ciper wrote:All catch cans suck.
All of them.

This on the other hand does NOT suck
http://www.mann-hummel.com/group/upload ... UCmOK5.pdf

I bet you'll gain some horsepower once the atomized oil has been removed.

Originally designed for large diesel trucks, so its quite large

I've never seen or heard of this particular design of air/oil separator before. But since all the links given are dead, it appears to be a Mann-Hummel ProVent 200. Link.

This is the first design I've seen mentioned in Subaru topics besides the Crawford AOS style units (expensive) that supposedly actually works decently (other than water separators for air compressors, which don't really match most engine bays). And I've read a bit on the topic.

Here is my set up, generic catch can removed oil level site tube and plugged holes it was leaking air. Then I stuffed the inside with stainless steel scouring pad. Installed and fired up and you could see the moisture immediatly in the line from crankcase, but line going to intake clean. It did seems to idle smoother. My engine runs high rpm on highway around 3900-4000rpms for 68-70 mph. I am curious too see if there is any froth in the line. No chance to test yet. My intake was pretty oily on the inside so, I hope this catchs some of it. I would like to buy an exspensive one but I thought for 22.50. I wold give it a try.

I finally found a happy setup with three catch cans. Intake dry!!!

I was wondering about the the hoese that run up the intake tube.

Lets see some pics of the three catch cans.

imtb wrote:Here is my set up, generic catch can removed oil level site tube and plugged holes it was leaking air. Then I stuffed the inside with stainless steel scouring pad. Installed and fired up and you could see the moisture immediatly in the line from crankcase, but line going to intake clean. It did seems to idle smoother. My engine runs high rpm on highway around 3900-4000rpms for 68-70 mph. I am curious too see if there is any froth in the line. No chance to test yet. My intake was pretty oily on the inside so, I hope this catchs some of it. I would like to buy an exspensive one but I thought for 22.50. I wold give it a try.

Do you have the other end of the line coming off the vent line coming from the back of the block?

Legacy777 wrote:

imtb wrote:Here is my set up, generic catch can removed oil level site tube and plugged holes it was leaking air. Then I stuffed the inside with stainless steel scouring pad. Installed and fired up and you could see the moisture immediatly in the line from crankcase, but line going to intake clean. It did seems to idle smoother. My engine runs high rpm on highway around 3900-4000rpms for 68-70 mph. I am curious too see if there is any froth in the line. No chance to test yet. My intake was pretty oily on the inside so, I hope this catchs some of it. I would like to buy an exspensive one but I thought for 22.50. I wold give it a try.

Do you have the other end of the line coming off the vent line coming from the back of the block?

a little primitive und untidy at the moment. I have two catch cans coming in a week or so to replace the temp ones. It will be all neat and tidy mounted on thd inner fender with a central drain

Last night I removed the line running up to the intake tube and plugged it. Now the crankcase breather is running through catch can and into PVC valve. Here are the pics. No chance to test drive, waiting on my 02 sensor.

Here is hose running up to intake tube.

Hose removed and plugged

Plugged intake tube

Maybe I missed it in the pictures, but do you have a line that tees off from the catch can back to the intake where you previously plugged the line coming from the crankcase?

No hose going to the intake tube from CC, i capped the spot on the intake tube. Shiny spot in t bottom pic hard to see.

The intake tube has two hoses one from each valve cover and that it.

Would it be better to take one from CC to the intake tube where I can it off? I can picture this and guess it would pull more out of the crank case and be filtered throught the CC, instead of with just the PVC valve like I have it now.
Man your pretty observant that you caught that.

CC can is complete, routed third hose from catch can to intake tube. I drove the van in today and check the hoses and surprised by how much gunk was in the hose from the crank case breather. The hoses to the Intake tube and PVC vavle were clean. You can kind of see in the pic.

Ok, yeah the setup you currently have is correct.

The PCV system needs to have two outlets from the Catch can, the PCV valve and inlet tube. This is because at higher rpm, engine vacuum is not that high and most of the vapors will be drawn into the inlet tube.

This is a great old thread ! Miss all the amazing info on here. I’m planning to revamp my 2 ghetto catch can setup and redoing my intake system while going MAFless.

Is there any Air/ oil separator alternatives now ?

There may be, but you're still likely going to have to retrofit it to our cars.

Gonna look into the Mann Provent 200

I run a triple catch can set up. It works great 0 blow by issues. A good friend of mine drew this diagram up for me, works great!



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I wouldn't recommend blocking the vent that distributed pressure between the heads and crankcase.

It may work, but if you're designing a setup I wouldn't suggest blocking it.

What the Pcv breather on the front of the 22t?
It’s the only ej that has it and really not necessary, plus if you build a hybrid the cross over pipe is way too tight to fit over it unless you run your stock cross over pipe


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