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Discussion Starter · #1 ·
For the past 25k miles i've had no pcv valve, i just put a 90 degree barb in there and then ran a hose from that barb to my catch can with a breather and also the line that goes from the side of the valve cover to the catch can with the breather. You'll find alot of people with it done up like this. It's wrong, and i didn't discover this until just last night.

Think about this for alittle bit....yes, it's ventilating the crank case pressure and it's doing it well enough to make the dip stick pop out and it's doine it well enough to accumulate some oil in the catch can after a few weeks, but the nasty gases remain floating around in the valve cover damaging and breaking down the oil....

This is where an evacuation system is needed. A force is needed to suck everything floating around in the head out of the head and into a sealed catch can. How does the sealed catch can produce a force to suck? From vacuum supplied to your intake pipe before the turbo. Vendors mostly sell them without the barb on them because the idea is to eliminate the oil in your intake system. That's understandable as the stock hose goes directly from the valve cover to the intake, so all we have to do is still something to take out the dirtiness before it get's sucked into the intake. Leave the pcv valve alone and have it hooked up to the IM, because it's doing you good. It's sucking out the fumes into the IM only under vacuum and when the IM shows +pressure then the ball shuts in the valve and the pcv valve closes so your not shooting a bunch of pressurized air into your valve cover. Now the evacuation system is left to the vacuum source from the intake pipe before the turbo, which always has -pressure.

Some of the crankcase pressure could cause blow by on worn rings, it may even cause more heat in the engine leading to perhaps detonation.

:eek: , it's been discussed many times before but i think alot of people don't think about it enough.
 

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oldman said:
For a PCV system (both PCV vavle and breather) to work effectively in ventilating the crankcase, they must work together as a team. While the system is under boost, PCV closes and ventilation is done through breather via vacuum in the intake pipe. While the system is under vacuum, PCV opens to relief pressure but more importantly, to remove blowby/contaminates from the crankcase then replace with fresh/metered air pulled in through the breather, this is the second part of crankcase ventilation that most seems to ignore, most only focuses on pressure relief.

Possible problems with other options:

1. Keeping PCV intact while venting the breather: Most running this setup will experience excessive crankcase pressure when under boost due to lack of vacuum coming from the intake pipe which can lead to dipstick pop out, leaky valve seals, tubo seal and gaskets. Less importantly, your AFR will go slightly leaner due to unmetered air.

2. Venting both PCV and brether: Pressure relief is not as big of an issue (provided that pcv is replace by a straight fitting) but because vacuum is completely removed, there are no ventilation and most blowby and contamintes will end up in your oil system. Less importantly your AFR will go slightly richer due to disabling the pcv vavle. Not a big problem for a track only cars but a DD is a different story.

You can easily maintain the integraty of your pcv system while keeping your intake tract clean as well as addressing the known leaky OEM PCV.

PCV side : IM -> heavy duty check valve -> inline/sealed catch can -> PCV valve -> VC

Breather side : VC -> 2nd inline/sealed catch can -> intake pipe
i did this write up on a local board here in missouri:

green_bread said:
Heres a good way to keep boost pressure from your intake manifold from entering your crankcase through a crappy/worn out PCV valve using a check valve and a filter/catch can for an air compressor. Here are the parts you need:

Huskey mini general purpose filter
2 1/4" to 3/8ID hose fittings
US Plastic - 3/8" Kynar® Liquid/Gas Check Valves SKU:64175 ($1.50 a piece from usplastic.com...Will work with vacuum between 2 and 29 in. Hg. and pressures from 1 psi up to 150psi)

Here is a pic of the stuff you need:


Basically, you keep your stock PCV valve, run a 3/8 hose to the filter, then run a hose from the other side of the filter to the check valve then a hose to the intake manifold. Watch the filter, they have a certain way the air is supposed to flow through them, and you will want to make sure to install the check valve so that vacuum can come from the crankcase but it will not allow the boost to pass the valve.
 

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dsms4ever said:
Some of the crankcase pressure could cause blow by on worn rings, it may even cause more heat in the engine leading to perhaps detonation.
Worn rings cause crank case pressure and blow by.But sometimes your pcv valve is not functioning properly.That would cause you dip stick to pop out also.
 

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Discussion Starter · #4 ·
Sorry, your right.

My problem is, i've tapped the valve cover for the 90 hose barb and removed my pcv valve. Now what do i do that will look sanitary? Is there such than as like a dual barbed pcv valve?
 

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drcustom said:
Another cheap fix is an inline fuel filter. You can see when it's getting filled up and replace/drain it.
That's what I'm running right now. I was running it to atmosphere but I read where its not good for the rings. After I switched it back to the intake, my gas mileage went up and my smoking stopped. FWIW.

I already posted this same information in another thread. You can run a catch can but make sure it is run to a vacuum source.
 

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dsms4ever said:
Sorry, your right.

My problem is, i've tapped the valve cover for the 90 hose barb and removed my pcv valve. Now what do i do that will look sanitary? Is there such than as like a dual barbed pcv valve?
if i were you, id just pick up a new VC(can prolly find one on ebay/classifieds for $30 or so)... as far as routing the hoses, see my post above... some REAL good info in there!
 

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Hmm reading this I'm thinking of a new route for my setup. Would running both lines from the valve cover to a catchcan, with another line coming out of the catchcan (where the filter would usually be) connected to the intake work well? This along with the IM blocked off. LMK
 

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Discussion Starter · #11 ·
New valve cover....no way, lol, you must be kidding me. Here is what i'm thinking as we all know the pcv straight out all wierd. I already have the 90 in there, i will just get a hosebarb to female thread that would match the male threads on the pcv valve and just run it inline. This would make replacing the pcv valve super easy.

Do we even need a pcv valve?
Couldn't we just run two hoses with no valves or anything to a sealed catch can and then run vacuum to the catch can from the intake?
This seem's like you'd get the maxiumum suction.

What are the benefits of the pcv valve?
 

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Discussion Starter · #12 ·
Does it have to be a special catch can to do it the way i just asked and the way robcatch was asking about.



Is there a better way to run it than this? I guess i'm just trying to figure out the benefits of the pcv valve as it only lets stuff out under vacuum, not boost, so why not have no valve in there and have full vacuum all the time out of two barbs?
 

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dsms4ever said:
DAH, green bread you didn't answer my questions from up above, the reason i'm asking you is because you have had experience with this. Help. Like a few posts up i need input. Thank you.
i believe you will want to try to do something like the way i posted in the 2nd post of this thread. the whole system works together from what i understand on both sides of the pressure range... ie:

there is not enough vacuum from the intake side while in vacuum, so the pcv vavle opens to increase vacuum pulling the vapors out of the crankcase. when you go in to boost, the pcv is supposed to close and there is a LOT more vacuum in the intake from the turbo spooling which evacuates the vapors.

you have to understand that the pcv valve is a crappy design and more than likely will not hold up to the boost pressure coming from the intake manifold. that is why i am using the 2nd check valve between the IM and the pcv valve.. the smaller catch can will go between the pcv and the other check valve just to keep oily vapor off the check valve.

if you were to run both lines to a catch can, the systems would not be able to work together in this way... and the catch can pic you posted above looks like it has a drain fitting on the side. if you were using that, you would want to seal the drain, run one line to the crankcase vent(not the pcv) and the other side to the intake.

let me know if i have made this even more confusing now... lol
 

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dsms4ever said:
New valve cover....no way, lol, you must be kidding me. Here is what i'm thinking as we all know the pcv straight out all wierd. I already have the 90 in there, i will just get a hosebarb to female thread that would match the male threads on the pcv valve and just run it inline. This would make replacing the pcv valve super easy.

Do we even need a pcv valve?
Couldn't we just run two hoses with no valves or anything to a sealed catch can and then run vacuum to the catch can from the intake?
This seem's like you'd get the maxiumum suction.

What are the benefits of the pcv valve?

+1 Anybody? Sounds in theory a good idea.
 

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robcatch said:
+1 Anybody? Sounds in theory a good idea.
ill see if i can find the thread that was talking about the actual function of the pcv valve. the thread said something about how it sort of works like a 'restrictor' and that replacing it with a straight fitting didnt work right for some reason.... its been a while since i read it but i think it was something oldman posted if anyone wants to help me out with the search.
 

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Ok I understand now how the pcv valve works, but I do have one question. Is having the pcv valve absolutely neccesary? I mean in theory just the hose from the intake to catchcan will provide better results then having no vacum source. How much vacum is really needed to efficiently relieve crankpressure?
 
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