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Catchcan hose routing revisited

CP

Well-known member
I've got a catchcan mounted on the firewall below the injector resistor pack. Currently I'm running a functioning PCV valve which has the hose feeding into the catchcan. My valve cover breather elbow is hooked up to a small cone filter. So I've only got one line running into the catchcan, and then another line running from the can to beneath the car. The port on top of the CC is currently plugged, but can hold the small filter that I've got on my valve cover breather instead.

That small filter is dumping small amounts of oil on my CAS, which then drips all over my nice new freshly painted transmission. So I think I need to run a line from that to the CC.

My question concerns the line from the PCV to the CC. If it were routed like stock, it would feed into the intake manifold. So when the engine is seeing boost, the PCV should close due to pressure in the line. However with the PCV line routed to the CC, is it always open now?

I'm looking for comments on how both the PCV line and valve cover breather line should be routed to I'm not spraying oil and things work as they are supposed to in a stock setup.
 

Polish

Well-known member
How you have it now is no good. The PCV works off Vacuum, so it gets sucked open. Then as you said under boost it seals and only the other vent tube functions. However with it just running into the catch can its never open. So your other tube is doing all the work. You may get some conflicting information as I have seen this topic explode before on here.

However mine is mounted on the fire wall, with a tube from the Vent used to go to the intake pipe. The PCV was removed and replaced with the nipple from my OEM Intake manifold, a tube then runs from it to the Catch can as well. Then theres a filter on top of the catch can. To me this is the best way, but others may see it differently.
 

CP

Well-known member
So you're running with NO PCV valve?

I too have seen this discussed 10x, and would like a final consensus on the best way to do it without messing anything up. I really would NOT like to run a tube into the intake, as it just makes a mess. Does your setup get oil all over everything inside the intake pipe and then into the turbo?
 

JB

Well-known member
Cy,

i beleived the vent line on the head should go to the catch can, then a line from there to the intake. If the catch can is doing its thing, oil in the intake should not be an issue. also i dont understand the breather filter on top of the can. without it the system should function like stock while still removing the oil from the intake line.

Joe
 

Polish

Well-known member
Correct, no PCV. Maybe I worded it wrong but I have no tube going to my intake. I agree it makes a mess and isn't at all needed.

I will try to take a pic tonight but heres simple drawing of the way I feel is best and the exact way mine is done.

 

CP

Well-known member
Ok, SO I want to:

1) remove my PCV valve, install a straight fitting and attached a hose that runs to the catchcan

2) run a hose from the valve cover breather elbow to the catchcan

3) run a hose from the top of the catchcan to a fitting on the intake (just after the MAS, or just before the TB?). This would solve the issue of un-metered air, but at the same time introduces oil vapor back into the intake.

Or should I put the breather on top of the catchcan? This would mean it's venting to atmosphere and is losing metered air.

Sorry I'm having such a hard time grasping this. I'd like it to function as close to stock as possible, but at the same time prevent oil and oil vapor from gunking up the system. Maybe this can't be done.
 
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Polish

Well-known member
Ok, SO I want to:

1) remove my PCV valve, install a straight fitting and attached a hose that runs to the catchcan Yes

2) run a hose from the valve cover breather elbow to the catchcan
Yes

3) run a hose from the top of the catchcan to a fitting on the intake (just after the MAS, or just before the TB?). This would solve the issue of un-metered air, but at the same time introduces oil vapor back into the intake.

Or should I put the breather on top of the catchcan? This would mean it's venting to atmosphere and is losing metered airIf you want to run it to the intake you could, I don't myself. Do not put it at a boost source or you'll just have a huge boost leak. I'd stick with a Breather. There is no unmetered air, I am not sure where you got that idea. So long as you seal up the intake pipe spot where the tube used to be it's fine. Don't mind the bold but I needed my text to differ from yours.
 

CP

Well-known member
Alright, I think I've got it /ubbthreads/images/graemlins/grin.gif I'll hit NAPA for that vent tube to replace the PCV valve on the way home today. Thanks for the clarification Corey!
 

skivittlerjimb

Well-known member
I've read these Catch Can / PCV / Breather threads many times and I'm still a bit confused, but here goes (since I'm looking to purchase an RRE catch can soon) with my understanding of things:

The PCV "sucks" vapors out from under the valve cover when the intake manifold has vacuum. It does so intentionally to prevent said vapors from causing sludge, condensation, etc. in the crankcase. Under boost, the PCV shuts and the breather tube on the side of the valve cover does this job, albeit not as well, but instead of feeding the vapors to the intake manifold, it feeds them back to the intake piping after the MAS in the stock configuration.

The purpose of catch cans, it appears to me, is to reduce or eliminate these nasty vapors from being re-introduced into the intake stream, whether at the intake manifold or in the air intake pipe. The benefit is less sludge in the intake pipes, turbo, manifold, etc. From what I've read, most of the sludge in the intake is due to what the PCV sucks out, not what the breather vents out. On my car, which definitely has high rpm blow by, there is just a bit of oil inside the intake tube where the breather vent tube hooks in. I know there was plenty of gook inside the intake mani. the last time I had it opened. I assume this is from what the PCV deposits there (along with the EGR, but that's blocked off now on my car).

Given the above assumptions, to achieve the goal of actively sucking out the nasty vapors from the crankcase and still separating the oil out of said vapors, could only be achieved by putting the catch can inline in between where the PCV sits on the valve cover and where it's hose attaches to the intake manifold. With another fitting for the breather to vent to the catch can, a good oil separator set up inside the catch can, and frequent draining of the catch can, this goal could theoretically be achieved. Is any of the above correct? /ubbthreads/images/graemlins/dunno.gif

-Jim B.
1432/2000
166k, a bit of blow-by, but still happy
 

Polish

Well-known member
No problem. If NAPA doesn't have the fitting just pull it out of a spare Intake Manifold, surely you or someone you know has one. It will screw right into the PCV spot.

Jim you are mostly correct.

However you can't vent a catch can that is also ran back to the intake or intake manifold. Thats how unmetered air will get in. You either do it may way with a breather or do a sealed setup and just run a filter or catchcan between the Valve cover and Intake/Intake Manifold. You can't vent just one either, say you pull the pcv and run it to a vented catchcan but leave the intake pipe tube as is. It will pull air through the breather, through the catch can, through the valve cover and into the intake. Thus introducing unmetered air. Also go pull apart the intercooler pipes on a stock car with a lot of miles. They are full of oil from the intake tube vent hose, well on my cars they have been. I prefer my way, due to simplicity and the fact that it works and all the vapors can easily get out.

 
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skivittlerjimb

Well-known member
The cloud is lifting from my mind... thanks Stanford.

The only downside to your set up, I suppose, is that you're relying on positive crankcase pressure to evacuate the gasses under the valve cover, instead of having the intake vacuum suck it out through the PCV. On a properly functioning engine with frequent oil changes, good compression, clean plugs, not much blow-by, etc., I'm guessing this is not a big deal in the short-medium term, but might necessiate a few more looks under the valve cover to make sure nothing is building up under there.

It's OT, but my blow-by manifests itself by popping out the dipstick at the track (high rpm, full boost, prolonged, etc.) After crimping the end of the dipstick tube it still pops out a bit but with only negligible oily mess under the hood. I know I'll need a bottom end rebuild soon (166k on it), but am I asking for trouble? I assume if the blow-by pressure can't get out the dipstick tube, it'll find it's way to the valve cover vent and PCV valve, or else it will push on the back side of the crank seal and such and cause leaks there. /ubbthreads/images/graemlins/uhh.gif I recently put in a new PCV just to make sure there was no restriction for the gases there. Any good strategies for dealing with blow-by safely until I rebuild the motor?

-Jim B.
1432/2000
166k
 

RayH

Well-known member
One way of handling more blow-by pressure is removing the stock breather elbow, enlargen the valve cover hole and attaching a larger fitting. Doug Thomas did this on his valve cover.
 

Polish

Well-known member
Like I said the PCV does nothing at WOT, changing it wasn't a bad idea but under boost it's sealed. Also the intake doesn't suck the vapors out really, I mean it does in a sense but there is a lot more pressure than you think. More than enough to blow whatever out. You are right if there is to much pressure it will find a way out, BUT that doesn't mean there always is to much pressure. A worn out dipstick seal will blow under even normal pressure.

I forget the old Vfaq saying but it's something like this.

A half worn engine and half worn dipstick will blow out.
A new dipstick and tired engine will blow it out.
A new engine and old dipstick will blow it out.
A fresh engine and fresh dipstick is the way to go.

Crimping is not the answer at all, imho. Even at 166k your engine probably isn't to bad. Try a new dipstick and uncrimp the tube.

Ray is also correct, some install larger fittings on the VC. I only see this needed for the HIGH revving big power guys.
 
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jepherz

Staff member
The only way to keep the system functioning as it is intended, is to leave everything hooked up as stock (pcv, CC vent hose, etc.) but put something in the hose going from the CCV to the intake to catch the oil. I am trying out a disposable fuel filter to see how well it catches the oil.
 

CP

Well-known member
Got everything hooked up now as Corey has suggested, except I can't find the correct hose fitting to screw into the PCV valve hole in the valve cover. McMaster didn't have anything in the metric 10mmx1.00 size I'm looking for, and neither did my local NAPA. Any suggestions on where I can source this part?
 

Polish

Well-known member
I used the Nipple end from an Extra intake manifold. It screws right in. I bet someone will ship you one for literally nothing. Just put a WTB, lots of people have spare 1g Intake Manifolds laying around that I'm sure they could pull the Nipple from.
 

CP

Well-known member
I've got a NT manifold in my garage, so I'll take a look at that. I'm pretty sure it's got what I need. Thanks.
 

Just reviving this thread because of something I saw in a catalog yesterday. Jegs now sells an oil separator to use instead of a catch can. Jeg's part number 555-52205. That way your intake vacuum can still help evacuate crankcase vapor/pressure, but the oily residue doesn't coat your intake pipes and intercooler.
 

Polish

Well-known member
I was going to revive this thread as well. I have been reading quite a bit about the whole purpose behind it all. There are two pieces to the puzzle, I will start with the PCV. It only works in Vacuum as we know but actually does serve more of a purpose than I originally though. When you let off the throttle or sit at idle the PCV is constantly open and the engines Vacuum is pulling all the blow by, oil vapors, and such out of the crank/cam case. The other is the simple Vent tube which runs to the stock intake. Now as I see it this is nothing more than a high RPM pressure release. The intake pipe does have a large amount of suction but the large surface area of the filter doesn't cause enough restriction to cause an actual vacuum in the vent tube itself. It's more there to release pressure from the crank case at high RPMs which the intake then sucks in and pushes through your intake tract which is the result of oily intake pipes.

To some this may all be common knowledge to others it may not. However I never gave it much thought before other than I didn't want that crap in my intake and didn't think the PCV and Vent did much at all. The way I have previously suggested and the way my car is now is only for HIGH rpms race cars as I see it now. Any street driven car has no need to have it set up this way. I regret not giving it more thought before I suggested my way to everyone. While some may choose to still run this way I am switching back for a few reasons.

First of all the catch can is making my engine bay a mess. You can see an oily film on the firewall where it is mounted. The pressure in the crankcase at HIGH rpms is enough to push an oily air out the filter, this is not something I want after spending many hours getting my engine bay to look nice.

Second under Vacuum all that oily air, blow by, and so on is just sitting in the crank case with no way to get out. Only under load is it pushed out. The PCV in operation will suck all this out every time you get off throttle or sit at idle. Also even when cruising and not in boost. Where as it is now unless you are at high enough throttle to cause pressure nothing will be evacuated. This will also cause the oil to get dirtier and contaminated quicker. Because any blow by or burnt up oil floating around will instead of being sucked out will actually just get mixed in with the nice clean oil. Not to mention be blown out the catch can filter and all over the engine bay over time.

Third, there are NO benefits to having the PCV eliminated and Vent tube routed to the catch can other than a clean intake tract. Which instead becomes a oily filmed engine bay. Those with fresh engines may see less but it's still there. It will also depend exactly how you have it set-up. There are many different ways.

Another thing, I see many people with just a filter attached to the Valve cover vent tube. This is no good. Reason being is the PCV opens at idle and trys to pull all the crap out of the crank case and what do you know there is an open hole in the valve cover. So you are pulling air through that filter and into the intake manifold, thus unmetered air is getting in any time you are under vacuum. It also makes it less likely for the PCV to be able to create a Vacuum in the crankcase and pull all that stuff out because there is an open port which lessens it's ability to create any suction. Yes, as stock it's the same way because the tube just routes to the intake but at least thats not unmetered air. And there is some sort of pressure in the intake pipe. Albeit not much it is there. So the PCV can operate as intended and pull the vapors from the crankcase.

So really in order to have zero unmetered air enter the setup and to retain a functioning PCV which is there for a purpose other than emissions as I have recently found out there are only a couple options.

1. Get a new OEM only (no parts store brands) PCV valve and hook it up exactly like stock. The same goes for the Valve cover vent tube, run it straight to the intake pipe. This will be an OEM setup and your Intercooler pipes and Intake manifold will have an oily film inside.

2. Get a new OEM only (no parts store brands) PCV valve and hook it up exactly like stock with the addition of a small inline fuel filter or SEALED catch can to help collect come of the oil before it enters the intake manifold through the PCV port. Then run the Valve cover vent tube exactly like stock. This will keep the Intake manifold clean but the Intercooler pipes will still get an oily film inside. To not hard to clean once a year.

3. Get a new OEM only (no parts store brands) PCV valve and hook it up exactly like stock. Then run the line from the Valve cover vent tube through a SEALED can catch or fuel filter to prevent any oil blow by from entering your intake tract. With this method everything will stay clean except the intake manifold. I will be using this method because I plan on Water/Methanol Injection in the near future and it will clean all that like new once it gets cycled a few times. This will keep the Intercooler pipes clean for the most part but the Intake manifold will still get the oily film, if like me you want to or already do run Water/Methanol Injection it will pretty much keep it nice and clean.

4. Get a new OEM only (no parts store brands) PCV valve and hook it up exactly like stock. With the addition of a small inline fuel filter or SEALED catch can to help collect come of the oil before it enters the intake manifold through the PCV port. Then run the Valve cover vent tube through a fuel filter or SEALED can can to prevent any oily vapor from being sucked into the intake tract. This will keep everything clean but function like stock and keep the oil cleaner longer and prevent all the crap from sitting in the crankcase except under higher crankcase pressures.
_________________________________________________________________________________

The setup I have now like Many is just PCV eliminated and Valve cover vent tube both ran to a vented catch can, it will soon be removed for the reasons stated above. If you change your oil constantly and the car spends almost all its life at WOT high RPM this is fine, for any street like car there are ZERO benefits as I see it. Considering the all so common "dirty intercooler pipes" can be solved with the addition of a fuel filter or sealed catch can on the Vent tube and PCV line. While retaining the somewhat valuable effects of a PCV system.

Also as I stated above do NOT vent just the Valve cover vent tube and leave the PCV stock. It is letting unmetered air into the system under vacuum. Which some may not care I am extremely picky. No matter how you do it if the Valve cover vent tube is open to the atmosphere and you run the stock PCV it will pull air through the Vent tube port and into the intake tract under Vacuum. That is unmetered air. It took me a long while to understand what people were talking about when they were saying unmetered air could get it but I finally got it.

I do apologize to all who did it like I advised above as I would not suggest that routing anymore unless like I said it's a track only UBER high rpms car.

Like I said mine will now be bone stock with the exception of an inline fuel filter on the tube going from the Valve cover to the intake pipe. Long post I know and I can almost bet someone will still disagree after this giant explanation but thats OK. I just figured I would share what I have learned after a lot of research on such a simple subject that I just wanted to really understand.
/ubbthreads/images/graemlins/smile.gif
 

I agree with you, Stanford, its best to have the PCV valve and the valve cover vent tube in the stock configuration. That's why I posted that Jegs part number, because it is a sealed catch can that separates the oil and collects it and still allows you to rout the hose back to the intake tube (option number 3 that you listed.) I used to have a clear fuel filter on my vent hose but still found oily residue in my intake. Less than before, but it was still there. Hopefully the sealed catch can will work better at separating the oil while still allowing the vent system to work as intended.
 
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