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Valve cover vent + PCV question

I've done a little searching but didn't find much. However, I think this information is out there. I just can't seem to find it.

I want my valve cover vent to be routed like stock. From the valve cover to the intake pipe. But I don't want any oil in my intake. I'm not sure how a real catch can works. I am thinking oil would still pass through one under high boost circumstances. Is there a way to plumb everything so air can travel freely in both directions but oil can't get in the intake?

I thought about an in line filter, but it would just get clogged up with oil. I also thought about a pcv in reverse or a on way valve, but both of those would only let air travel one way as well.

Can someone explain the internal workings of a catch can to me? Does any one have any ideas how to accomplish no oil in my intake?
 

PJGross

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For the catch can, oil shoots in, slaps against the opposite wall, and slides down (hopefully) while air exits out another opening. I would think that angled inlets and outlets so that incoming air spirals around the sides and then exits out the center of the top, would be a great way to go. For the RRE can (old one), for example, you could plug the other side port, and put your line to the intake coming off the top where the filter would be.

There are posts on here using various filters in line, and I would think that would be a good secondary catch between the exit of the can and the intake.

RRE catch cans here

The new no-name catch can from RRE looks pretty slick. I never know how much is in my catch can, this seems like a good upgrade if I go with a two can approach to keep the PCV operational. Its a better design to separate oil, but you could still use a clear fuel filter as a double check for its operation.

-PJ
 
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stealthtt24

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the url button is fucked, but thats the thread i was looking at.
Im either going to go back to stock or have some sort of catch can between the valve cover vent and my intake pipe, pcv will be left stock.

URL button FTW
 
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PJGross

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just to add, no, the old RRE can does not to my knowledge spiral the air. I just suggested that that would be a nice design, kind of like that fancy vaccuum cleaner, or industrial particulate filters (for sawdust, etc). However, if using a return line, I would just avoid putting the return directly across from the inlet and you should be fine. I'd still exit out the top since oil particles are not dissolved in air, just suspended, and should slap the side of the tank anyway. The filter would be a nice check and if it looked clean after a few weeks, you could remove it or keep it as an indicator of something changing if you notice it getting full of oil at some point.

-PJ
 

iLLeffeKt vr-4

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i installed two in line fuel filters. one from the PCV to the manifold and the other from the side exit of the valve cover to the intake pipe. so far i've put about 200 miles on the car and not even one drop of oil in any of the filters. i think it would take a very long time for them to get clogged up. and when they do they're only $3 each at pepboys/autozone.
 

Quote:
Why would you want it hooked up like stock?



I don't want to eliminate the pcv as I have read it serves a purpose (active removal). If I leave the valve cover vent vented to atmosphere, when the pcv opens the vc vent will act as a vacuum leak unless it sucks metered air. I want to eliminate the oil in my intake from when the flow is in the opposite direction.

It sounds like an in line catch can or an in line filter or both will fit the bill. I'm just concerned that when the turbo sucks air, it will suck hard enough to pull oil out of the catch can.

Thanks
 

Catch cans are a proven solution. So are in-line filters. I use a cheap clear plastic fuel filter and it works great. After two or three months it will accumulate a little oil in the bottom but the filter material stays pretty clean...no evidence of clogging. Then I spend another 3 bucks and replace it.
 

jepherz

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Quote:
Catch cans are a proven solution. So are in-line filters. I use a cheap clear plastic fuel filter and it works great. After two or three months it will accumulate a little oil in the bottom but the filter material stays pretty clean...no evidence of clogging. Then I spend another 3 bucks and replace it.



I have the same thing on my car. So far I can see oil being collected, but I haven't really looked at the inside of my IC piping to be sure that NONE is getting through. Here's a pic:

 

BadVr4

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Dec 30, 2004
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678
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manchester, ct
why do you wanna run it into the stock intake? that blow by oil is bad for the turbo, just run a line from the breather and from the pcv valve to the catch can, and all problems solved!
 

TSigvr4,
I know the oil is bad for the turbo. That is the point of this thread. I want to stop the oil from entering my intake pipe. But if I disconnect the pcv (ie run it to a catch can) I will lose active circulation under the valve cover. The pcv serves a purpose other than just emissions. It sucks the crap out. It might be fine to disconnect it on a drag car because those don't run for very long and the oil gets changed very often. But a daily driver is different.
 
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TOF, you might as well just run the valve cover vent to a catch can. Having it plumbed to the intake ahead of your MAF like that is really the exact same thing. Your valve cover vent is still sucking in non metered air when the PCV opens. The only advantage to your setup is that the air is being filtered.

The reason to run that vent back into the intake, is so that all air entering the engine has been counted. Your AFM (in this case a GM MAF) is well down stream of where that valve cover vent is hooked up to. That vent sucks air right in through your cone filter, totally bypassing the MAF.
 

Quote:


I don't want to eliminate the pcv as I have read it serves a purpose (active removal). If I leave the valve cover vent vented to atmosphere, when the pcv opens the vc vent will act as a vacuum leak unless it sucks metered air. I want to eliminate the oil in my intake from when the flow is in the opposite direction.

Thanks



I've always wonder how this "unmetered air" from valve cover vent can get into the cylinders?
 
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"I've always wonder how this "unmetered air" from valve cover vent can get into the cylinders?"

Vacuum in the intake manifold sucks open the PCV valve and draws the unmetered air, along with any blow-by gases, directly into the intake manifold.
 

One more post and I will shut up for a while.

This appears to be a practical catch can. However the routing diagram is a little bit off for our purposes.

For our cars we would leave our PCV valve routing intact, and use the catch can on the "clean" side.

ebay auction
 

Quote:
"I've always wonder how this "unmetered air" from valve cover vent can get into the cylinders?"

Vacuum in the intake manifold sucks open the PCV valve and draws the unmetered air, along with any blow-by gases, directly into the intake manifold.



so if you have both line(pcv and valve cover vent)hooked up to catch can, it shouldn't have any unmetered air right?
 

CP

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My catchcan vent typically blows oil spray all over that side of the engine bay. I'm currently running NO pcv valve. I've routed both the valve cover and pcv outlets to my catchcan. The useless filter sits on top of it.

I'd like to get this back to as stock as possible by:

1) Adding an inline filter to the valve cover vent and running that beneath the car and out.
2) Re-installing the pcv valve and routing a hose from that to the catchcan.
3) Blocking the second inlet for the catchcan, and running a hose from the top outlet to a port on the intake manifold. This way the pcv valve is vaccuum activated, but the catchcan can hopefully catch oil in its liquid form before it gets to the intake mani. Obviously oil vapor can still pass to the intake.

So in this case, I would not be doing anything with the metered air coming from the valve cover vent.

Would this setup work, or will something screwy happen? I'd like to get the pcv valve back into the system and operational.
 

Polish

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When the PCV opens it will pull air out of the Valve cover. When you leave the vent tube open it can suck air through that and into the intake manifold, this will be unmetered air. Not much air but it will be there. After having my catch can a while and reading up on it more I too am going to put a pcv back in. I am going to tap my Dejon intake pipe for a barb fitting though and do it exactly as stock, with the exception of a catch can between the PCV and IM and filter on the Valve cover vent to Intake pipe hose to try and stop oil build up.
 

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