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Boosted K20A3
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65 Posts
Alright, how about a diagram? Taken from the PCV system description in the Helms.

Number 20 is the PCV valve. I have a hose going to my catch can.

On the catch can, I have a tee which leads to two outlet hoses. Each of these outlet hoses has a check valve that only allows flow away from the catch can.

When idling, the IM is the highest vacuum, so the CV closest to the IM is open, which closes the CV on the compressor inlet side.

When under boost, the positive pressure closes the IM CV, and the compressor inlet is generating a stronger vacuum to pull air through the catch can.

Also of note, the PCV valve is never truly closed, whereas the check valves can be. Honda designed the PCV valve to "leak" and essentially allow airflow both directions, with the predominate airflow of course being to vent towards the intake manifold.

Many people tackle this different ways, but this is the way I felt satisfied the original intent of the factory system.

For reference, I didn't include the BOV portion in this. I did include the valve cover vent method I chose, though. This is the hose you can see in my second picture with the 90° bend.

Hope this helps!

 

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GTX35R
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30,385 Posts
lmao i just drilled mine and had a filter on it lmao
I think that's what I am going to do for now. Got to much other crap to work on.
 

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Registered
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1,076 Posts
6262 E85 K24 and I run as stock right into the intake. Not saying that's the way to go, but I have zero issues and it runs as well as the stock motor, well + 300hp.
 

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Boosted K20A3
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65 Posts
Just don’t delete your PCV valve and run IM boost pressure into the crankcase. Your stock PCV also doesn’t shut/seal, like I said earlier and like how a standard oil/fuel rated check valve will.
 

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GTX35R
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30,385 Posts

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GTX35R
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That one says to run to the compressor inlet, so there’d be no worries of boosting your crankcase there.

Man I wish that’s all I paid for my setup 🤣
Lol yeah i'm getting cheap right her at the end. I've spent way more money than I should have. But it's so close. Just ready to get her running again. Hoping to drop the motor in tomorrow. Got to run to LKQ and get some bolts and other stuff.
 

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GTX35R
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30,385 Posts
That one says to run to the compressor inlet, so there’d be no worries of boosting your crankcase there.

Man I wish that’s all I paid for my setup 🤣
I was reading about that catch can. Since it's "filtered" can't I just cap the outlet side and run the pcv to the can?
 

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Boosted K20A3
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65 Posts
I was reading about that catch can. Since it's "filtered" can't I just cap the outlet side and run the pcv to the can?
I don't have any experience with one, but you would then be relying on positive crankcase pressure pushing the vapors into the catch can instead of allowing a vacuum source to pull it through. I imagine it wouldn't be very effective, but others can chime in on that note.
 

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GTX35R
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30,385 Posts
Anybody have a type s clutch case or tranny for sale? My clutch case cracked. FML
 

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GTX35R
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30,385 Posts
Has anyone used gear driven inc?

I'm going to have him build my transmission and I wanted to see if anyone had used him before.
 

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Shazaam
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4,596 Posts
Why would you run a check valve inline of the hose running to the compressor inlet? There is no way for the inlet to generate positive pressure so the check valve isn't doing anything other than keeping the crankcase from having a clean air supply. You want that open when the IM is pulling vacuum so that you have a "clean side" for your crankcase to replace the "dirty" air being drawn into the catch can during manifold vacuum.

I've tried everything from dual cans(one clean side draft can, one dirty side pcv can), 3 port cans, single vented pcv can, etc and I've always had the best results with either the dual can or 3 port cans. You also need to be aware of the size hose you are using the amount of crankcase evacuation it is capable. Putting that check valve on the inlet side may generate a very, very, very minor amount more vacuum on the crank case but it's really not worth it.

Most of my PCV experience comes from dealing with LSx motors and now the RB26 which are notorious for crank case pressure problems blowing out seals.
 

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Boosted K20A3
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65 Posts
Why would you run a check valve inline of the hose running to the compressor inlet? There is no way for the inlet to generate positive pressure so the check valve isn't doing anything other than keeping the crankcase from having a clean air supply. You want that open when the IM is pulling vacuum so that you have a "clean side" for your crankcase to replace the "dirty" air being drawn into the catch can during manifold vacuum.

I've tried everything from dual cans(one clean side draft can, one dirty side pcv can), 3 port cans, single vented pcv can, etc and I've always had the best results with either the dual can or 3 port cans. You also need to be aware of the size hose you are using the amount of crankcase evacuation it is capable. Putting that check valve on the inlet side may generate a very, very, very minor amount more vacuum on the crank case but it's really not worth it.

Most of my PCV experience comes from dealing with LSx motors and now the RB26 which are notorious for crank case pressure problems blowing out seals.
It doesn't matter that the compressor inlet never produces positive pressure. Relative pressure is what matters. At idle, vacuum is higher (lower absolute pressure) in the IM than the compressor inlet, which is also a vacuum but is a lower vacuum (higher absolute pressure). The check valve ensures the IM isn't drawing air pre-compressor and is instead drawing air (if any) from the PCV system through the catch can.

Also, my system uses a stock style PCV valve - not a drilled out or removed valve like others do.
 
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