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PCV hose size

N

Naffy

Passed Driver's Ed
Hi all,

I recently installed the IE short runner intake manifold and a generic non baffled catch can(I know, but it was free). And I was having some issue where I turned out to have the wrong tubing which would collapse under vacuum. I now have fuel line of the OE pcv size, stepped down to about 5/8" iirc into the catch can, then same size out, stepped down to one of the smaller IE manifold vacuum ports. So, my question is, is there a size hose I should be keeping the vacuum Lines at? Or is stepping it down as needed ok as long as it's holding vacuum? Also have new valve cover and gasket for unrelated reason so it's also a new pcv.

Thanks in Advance for input.
 
OrangeSpy

OrangeSpy

Ready to race!
Honestly I have no idea, but if the set up you have works then it works! haha.

How did you get the free catch can?

Sent from my SM-A520W using Tapatalk
 
W

Wascally Wabbit1

Drag Racing Champion
I was told by IE not to use the vacuum ports to vent the valve cover as they are too small to allow enough flow through. The largest one is 1/4" and I'm not sure what the actual openning is but its small. You generally want as big an opening as possible to vent the valve cover. 5/8" is probably fine but I would not go any lower. You should run the pcv line to the air intake between the filter and TB. To small a vent on the valve cover leads to too much pressure which can cause all sorts of problems like blown seals.
 
N

Naffy

Passed Driver's Ed
Had it laying around from a few years ago, so I considered it free haha. I wasn't about to go buy a new one if I didn't need.
 
N

Naffy

Passed Driver's Ed
Ah ok. You just responded as I did. I don't have an open port on the intake tubing so I'd have to figure that part out.
 
M

MLue1

Drag Racing Champion
I measured the PCV connection on one of the VW intake manifold (IM) bits and pieces I have laying around; it has an ID of 3/4 inches.

As WW said, you should keep the hose diameter large, the flow of blow by gasses is determined by the PCV diaphragm, in the case of a catch can you don't want the flow to be too fast, so a large diameter (slower flow) gives the catch can baffles/filters a better chance to remove the oil droplets.
 
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N

Naffy

Passed Driver's Ed
Alright, I'll see what I can do at this point. My main concern is if the pcv will open or not, which I assume it will due to the presence of vacuum? Understood flow rate will likely change.
 
W

Wascally Wabbit1

Drag Racing Champion
I am sure it is at least to some extent. I wouldn't worry about it but I probably wouldn't make that a long term solution. Especially if you like to get on the gas. I have mine vented to ATM with 3/4 line and that hose it definte pumping out some vapor. I was thinking of venting mine the same way so I called IE and asked their advice on the matter and they said the vacuum line on the manifold were meant for running things like the brake booster. I think it's still doing it's job routing the pcv to the manfold and may actually be plenty of vacuum not sure but it seems small for how much has to go through it.
 
N

Naffy

Passed Driver's Ed
Fair enough. I just replaced the valve cover with an OE type replacement but probably should have just bought one with pcv delete. Anyway, I'll see if I can maybe T it onto the similar size hose going into the intake( hacked up usp intake, only has 1 port on it from stock anyway) I believe that would be for vacuum pump? I'll figure that out next.
 
W

Wascally Wabbit1

Drag Racing Champion
Ya its sucks as the only intake that has all the ports is the IE one specifically for the IM which is 400 bucks. I was running your setup. Cut up USP intake. I got a used pflow for a hundered bucks and am going to use the USP piece instead of the oem plastic piece in the heat shield which will give all three ports. I am not 100 percent sure it will work the way I want it to but I still have the valve cover vented to ATM for now.
 
FlowMK6

FlowMK6

Ready to race!
The inner diameter is 3/4", I cut the connector of the stock PCV hose and used a rubber 3/4" hose and for the catch can I vent it to atmosphere



I would use the closest hose size from 3/4"

I also removed the PCV diaphragm to make it a straight port, not needed anymore since atmospheric pressure isn't variable like the vacuum from the engine
 
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