Head breathers and crankcase PCV setup

[Subru]

I want to sort my pvc setup before getting my retune for my V7 Sti and have a few questions.

 

Would running a three port catch can with one port for both head breathers, second port for crankcase vent and the 'clean air' port (third port) to just run underneath the car instead of back into intake be okay?

Are there any issues letting 'metered air' escape? Id rather let the air go to atmosphere as I bet there is still somehow still oil or other crap in the 'clean' air. Its also easier in my case to just vent it carefully underneath the engine.

Also is it fine to combine the head breathers and crankcase breather into one can? Some people say you should normally run a dual can setup but is that actually necessary?

Id still be catching the oil like a normal can.

Most people just catch the head breather air and be done but the EJ207 has the 3rd crankcase one. This third one (if im correct) under boost pushes air into the intake pipe (pre turbo) and under vacuum it goes into intake manifold.

So for this one id just unplug the hose to the intake pipe (pre turbo) and run to catch can but what do I do with the hose that goes to the intake manifold, block it or keep it?

If catching the crankcase crap isn't worth doing, ill just keep it standard.

Hope thats not confusing to read lol.

[Loren]

The air going into the catch can is not metered air... it can be vented to the atmosphere.

 

The biggest thing to be worried about it is not restricting the flow from the heads and crankcase with small ports on your breather.

I use a 4 port can... one port for each breather appropriately sized... and one large breather port on top which I vent under the car.

 

Block the paths back into the intake pipe and remove the pcv and block that port too... though some people would prefer to keep it.

 

[Subru]

11 minutes ago, Loren said:

The air going into the catch can is not metered air... it can be vented to the atmosphere.

 

The biggest thing to be worried about it is not restricting the flow from the heads and crankcase with small ports on your breather.

I use a 4 port can... one port for each breather appropriately sized... and one large breather port on top which I vent under the car.

 

Block the paths back into the intake pipe and remove the pcv and block that port too... though some people would prefer to keep it.

 

Ok very helpful. Thanks. 

 

So where ecactly is the pcv for the crankcase? Is it on the block or intake manifold?

[Loren]

22 minutes ago, Subru said:

So where ecactly is the pcv for the crankcase? Is it on the block or intake manifold?

 

On the intake mani, directly under the throttle. So there is the crankcase breather port... it has a plastic T section... one side goes to the intake pipe, the other goes to the pcv.

 

Some newer blocks have two crankcase breathers... I just blocked the second one up when I had one of those... I don't know how it is plumbed into the OEM system at all.

Edited February 25, 2021 by Loren

[Subru]

12 minutes ago, Loren said:

 

On the intake mani, directly under the throttle. So there is the crankcase breather port... it has a plastic T section... one side goes to the intake pipe, the other goes to the pcv.

 

Some newer blocks have two crankcase breathers... I just blocked the second one up when I had one of those... I don't know how it is plumbed into the OEM system at all.

Ok thanks. Ill hopefully get this done this weekend.