Oil catch can - using T to connect PCV and breather???

[tsi1991awd]

So I'm installing a catch can that I made from a Husky filter element used for air compressors. It has one in and one out on it. Can a T fitting be used to connect the PCV and breather hoses and then have one hose into the IN portion of the catch can?

I'm not sure if the T will interfere with oil flow into the can (if any oil comes out at all) that is my main concern.

 

[No_Skillz]

Kenamod, PCV doesn't actually meter air - it doesn't measure anything. It simply lets a certain amount of air through. This same thing can be accomplished with the barbed fitting and a checkvalve. Granted, the amount will be differ, but if everything is the same diameter it shouldn't be a problem. I have added a checkvalve and a husky canister to my own car and a friends car and neither affected it enough to have to play with the BISS screw.

However, I never noticed about the materials compatability with the husky can and gasoline. I'll have to keep an eye on that. Thanks for the heads up.

 

[tsi1991awd]

I've yet to experience any fluctuation in idle in the different ways I set it up. The only thing I can think of that would be different in the PCV or just a check valve is that under more vacuum, the PCV will open further...with the check valve it'll always let the same amount of air out....well something to that effect. Hard to explain what I'm thinking.

 

[kenamond]

Kenamod, PCV doesn't actually meter air - it doesn't measure anything. It simply lets a certain amount of air through. This same thing can be accomplished with the barbed fitting and a checkvalve. Granted, the amount will be differ, but if everything is the same diameter it shouldn't be a problem. I have added a checkvalve and a husky canister to my own car and a friends car and neither affected it enough to have to play with the BISS screw.

However, I never noticed about the materials compatability with the husky can and gasoline. I'll have to keep an eye on that. Thanks for the heads up.

It meters air by letting a predictable amount to pass through. That's called a "metering orifice", and yes, the PCV valve is a metering orifice. And no, a check valve and barbed fitting is not the same. The PCV valve lets a specific amount of air to bypass the throttle body, and the car was designed with that in mind. A barbed fitting and a check valve will also let a certain amount of air past, but it will be different than the PCV valve will and will vary much more when the vaccuum changes, and this often messes with the idle (I've read plenty of threads related to this). The IASC will take up the difference in most cases, but if the IASC is close to the end of its "throw", you can hit idle surge and have to adjust the BISS. And the barbed fitting has no snorkel. Yes, you can work around it, but many folks don't realize what the PCV system does, alter it, then scratch their heads when stuff starts to misbehave. They use a barbed fitting and suck oil into the intake manifold or fill up their catch can in 5 minutes. The idle is whacky, or they blow the dipstick tube out of the block, or their oil smells like gas, or unknown to them, their motor wears out a bit faster over a couple of years.

There isn't any good reason to remove the PCV valve on a moderately modded daily driver. You can add catch cans and check valves, and that's all good as long as you do it correctly, but you can also just do a boost leak test every now and then and replace the PCV valve whenever it starts to leak.

I suspect (and I think I may try this) that you can use the crappy $1.50 Autozone PCV valve (or an old, leaking OEM PCV valve) with a $0.50 USplastics check valve and get the same behavior as a new $8 OEM PCV valve. It'll save you $6 in the first pop, and then you just have to replace the check valve when it gets gummed up and starts leaking...so $0.50 check valves can be used instead of $8 OEM valves in the future. The cheap-o PCV will properly meter air and has a snorkel. The cheap check valve serves the role that the OEM units tend to fail in...closing securely under boost. If you put a catch can in between, the check valve will probably last longer, but at $0.50, how many would you have to replace in order to justify paying for a $75 catch can? Even if it was one per year, it'd take 150 years.

 

[tsi1991awd]

Good point. Would a PCV for a different car work? Say one that has 1/8NPT threads? Or are they "metered" differently?

 

[romeen]

tsi1991awd, the thread pitch of the oem PCV valve is very close to that of 1/8 NPT. Close enough that the stock PCV will still screw in and hold just fine even though you used a 1/8 NPT tap on it. Try it out, you should be fine.

Side note: I'm pleasantly surprised at how popular my little discovery (the USPlastic check valve) has become. I see it come up in so many different threads as well as on that "other" forum. I never would have guessed when I first mentioned it in the "Stupid PCV" thread. I'm glad it's working out for so many guys.

I guess I've had mine in longer than anybody else and it's still holding perfect. Strong suction through PCV when in vacuum and not even the slightest hint of leakage when I pressurize my intake to 25psi.

 

[tsi1991awd]

Hey man. Yea I tried to just screw the barb fitting into the PCV hole but it didn't go in so I had to tap it...I'm not sure if the stock PCV would actually fit. I might get one tomorrow and try to screw it in. If it works then it'll save a lot of bickering and bs,

 

[kenamond]

And just to be clear, if your VC is stripped and you can't thread an OEM valve into it, you are one of the rare exceptions...do what you have to do. My harping in this thread is intended to dissuade others from tinkering with their PCV system unless they know what they're doing (which is different than thinking that they know what they're doing ). Everyone is tempted to put a couple of catch cans under the hood for good measure, but if you don't do it correctly, you do more harm than good.

Hope a stock PCV will work for you.

As far as getting another PCV that threads in and meters the same, who knows, but if you have the check valve, you can try a couple $1.50 Autozone PCV valves and see if any work out for you. The "DSM" PCV valve they carry doesn't seal under boost, and others might not either, so that's why you'd need the check valve as well.

 

[fuzzydoodle]

Whatever you do, do NOT get a fram filter of any kind, I sent my GF to get a PCV valve once told her specifically DONT GET A FRAM, what did she come back with....
You guessed it, figured oh well, pulled it out, gave er the ol' blow test, was able to blow through both ways right outta the package.
So I pretty much boycotted them right then and there.

But in your case I would just be careful if you do try jimmy'ing a "snorkel" into the barbed fitting, cause like it was said I really dont think the outcome would be good were that thing to come out.
Just scary business, be careful.

But for all other options being exausted, try it, like stated earlier you would be a rare exception and to overcome this problem would be a great knowledge bank, should this problem occur on another's car.

Also I looked at the pics for this USplastics valve, for anyone using them, what is the barb dia.? Reason I ask the pcv valve is rather large, as so the hose is also, is the valve the same in diameter? or would some sort of hose combination be needed to run this? (no intention of thread jacking, future knowledge bank only)

 

[kenamond]

Actually, every non-OEM PCV valve I've seen leaks. They weren't designed for forced induction applications. I checked Autozone and Carquest units while standing in the store, and someone who'd sold their '95 Tsi-AWD gave me a spare PCV valve of yet another brand, and it leaks, too. But...they cost $1.50. And a check valve costs $0.50. Put them together and you may have a $2.00 PCV valve setup that works.

And the USPlastick check valve barbs are a bit larger than the PCV valve barb.

 

[tsi1991awd]

Actually the check valves come in different sizes. I'm running a 3/8" hose all the way, so I got the 3/8" check valves. The breather nipple is 3/8 and the PCV looks the same.

 

[fuzzydoodle]

Yeah I figure every aftermarket one is garbage, I pretty much stopped running anything other than OEM mitsu stuff, for the fact. But still you should NOT be able to blow through both ways right outta the package, I know I cant blow worth 21lbs of boost (please refrain from any commenting, ) so turbo or not it is only suppose to allow air one way and it could not even do that brand new.

Oh thats good to know they come in different sizes, perfect. Thanks.

Oh and kenamond, please take a look at the "oil cooler pictures" thread I have something posted there I could really use your knowledge on.

Ok deviating from topic, done now.

Let us know when you get your check valves and how that whole situation turns out. Did you ever try the threads on the pcv to match the barbed fitting? I was curious if they were the same thread pitch.

 

[kenamond]

In a normally aspirated motor, the intake manifold pressure is *always* lower than the crank case pressure, so the PCV only goes one way in those cars.

 

[tsi1991awd]

Yeah I figure every aftermarket one is garbage, I pretty much stopped running anything other than OEM mitsu stuff, for the fact. But still you should NOT be able to blow through both ways right outta the package, I know I cant blow worth 21lbs of boost (please refrain from any commenting, ) so turbo or not it is only suppose to allow air one way and it could not even do that brand new.

Oh thats good to know they come in different sizes, perfect. Thanks.

Oh and kenamond, please take a look at the "oil cooler pictures" thread I have something posted there I could really use your knowledge on.

Ok deviating from topic, done now.

Let us know when you get your check valves and how that whole situation turns out. Did you ever try the threads on the pcv to match the barbed fitting? I was curious if they were the same thread pitch.

The thread pitch is different. I'm sure if I forced it, I could thread it in, but I didn't try

I got the check valves in yesterday but it was raining too much to do anything, so I just put one in today. I have it AFTER the PCV catch can but BEFORE the intake manifold. There was a bit of oil in the can to begin with, so I left it there. I started the car and noticed that it did move around a LITTLE bit in the bottom of the can, but NOT NEARLY as much as it did without the check valve. When I had no check valve, it was sloshing and waving all around on the sides of the can and getting sucked up.

Now it barely moves because the air flowing across it at the top. I went for a short drive down the street, boosted through third gear and came back. To my surprise the same amount of oil was in the can, and only a small trickle down the side from new oil/blowby that was sucked into the can. Looked at the breather side catchcan and there was hardly anything new.....it had sucked out some weird shit from this past week or whatever. Some cream colored grease looking stuff....maybe a mix of gas/oil and whatever other nasty stuff.

Also, there was no oil in the check valve, so I assume it hasn't sucked any up. And hopefully won't. Anyways, just letting everyone know that a check valve WILL work and there seems to be no need for a PCV right at the moment...

 

[romeen]

Although it seems to be working out I would still consider using the PCV valve instead of a NPT fitting. The "snorkel" of the PCV will help to prevent oil getting sucked through the system.

I ran my system per the RRE instructions for a couple years meaning I tapped the PCV opening with a 1/8 NPT tap. When I decided to go back to the stock configuration I thought I was screwed as far as being able to thread in the oem PCV valve. I tried it nonetheless and it screwed right in and held tight. Been that way for a few years now. It threads right in without any wobble or slop and leaks no oil whatsoever.

If you do stick with the fitting let us know how it's working out after a couple thousand miles. It would be nice to be able to get a larger volume of fresh air moved through the crankcase than what the small diameter of the oem valve will allow.

 

[tsi1991awd]

I may go buy a PCV from Autozone or possibly the dealership. As of right now, the barbed fitting is working out. Ill keep you posted on how it holds up. I drive about 500 miles a week for work, so it shouldn't be a problem

 

[boostforfun]

ok, I am more of a visual guy, so try this. Am I understanding it correctly, or am I missing something. I think the check valve is prob. backwards.

Thanks.
Brian

 

[DougR]

They are both backwards.

The air charge flows from the VC through PCV, CC, USP CV, and finally into the IM.

 

[tsi1991awd]

ok, I am more of a visual guy, so try this. Am I understanding it correctly, or am I missing something. I think the check valve is prob. backwards.

Thanks.
Brian

Like this.

 

[boostforfun]

good, I was only completly bass-ackwards... This is why I ask, because the way I had it drawn up looked wrong, but that is the way my brain processed it.

Thanks!
Brian

 

[tsi1991awd]

Yea, the way you had it, it would boost the crankcase but it wouldn't let ANYTHING out when under vacuum because of the check valve.

I've been on about 750 miles so far and I do not have much oil in either catch can. I check when I get to work and then when I get home. There's no oil in the check valve, which means it's all staying in the catch can. So this is a good thing. You CAN use a barbed fitting....you can argue it all you want, but it's working just fine for me.

 

[nytescion]

Could I remove my pcv line going to the intake manifold. Route both lines coming off the valve cover together. then into a sealed catch can and then run a line from the other side of my catch can to my intake pipe? Reason i'm asking is because I'm tired of all the leaks I'm getting from it (the rubber hose). I would like to get rid of port in the intake manifold. plus there is too much in that general area anyway (harness, injector, stock black plastic crap, fuel rail flange.

 

[blcknspo0ln]

No, you cannot do this in order to maintain the operation of the PCV. It is a one way check valve that uses the intake manifold for boost/vacuum to open/close it. If you want to set it up right you need to do two separate catch cans.

IM > catch can > PVC & Valvecover > catchcan > intake pipe.

If you want to eliminate your PVC, you need to get the appropriate fitting and replace the PVC with a straight fitting. Then you can block off your IM line, and run both lines to your intake pipe.

 

[nytescion]

Hmm. I would think that the check valve is only there to stop from pressurizing the crankcase while in boost. If there is constant vacuum on the check valve it will never close right? so what would be the difference of the turbo putting constant vaccuum on the check valve? wont it just act as a fitting straight threw fitting anyway? (I'll use a fitting just incase). What I'm trying to do is eliminate the intake manifold all together.

 

[AWD_Hybrid]

I use 1 can, pcv in & breather in, hose to intake has a bung &
a 90deg fitting at the rear of my can faces the ground
I hate oil in my inlet. My car is not a 2 stroke lawn mower.
Cheers !

 

[nytescion]

No, you cannot do this in order to maintain the operation of the PCV. It is a one way check valve that uses the intake manifold for boost/vacuum to open/close it. If you want to set it up right you need to do two separate catch cans.

IM > catch can > PVC & Valvecover > catchcan > intake pipe.

If you want to eliminate your PVC, you need to get the appropriate fitting and replace the PVC with a straight fitting. Then you can block off your IM line, and run both lines to your intake pipe.

could you let me know why i would need to replace the check valve and put a straight through fitting in?