Catch can - vent both to atmosphere and into Y-pipe depending on pressure level

[julex]

I currently have mann oil separator system installed on my 2.7 which replaces stock PCV system and has return to Y-pipe for clean non-smelly car. The system also drains separated oil back to oil pan.

Today I started thinking about this a bit more and would like to modify the system to return to y-pipe when there is relative vacuum in the manifold and vent to atmosphere when the car is under boost. This would make PCV system effective during DDing as all the vapors would get burned off, and at the same time it would prevent these blow by products entering intake path during boost to prevent HP loses associated with that.

This should be relatively simple to do with the return line to y-pipe by using diverter valve on that hose and vacuum side hooked up to the manifold so that it stays open during vacuum. I would have to experiment with adjustable diverter valves and find one with super soft spring so that is stays open under low vacuum, but it is not a b ig deal at all.

The atmosphere side I can't figure out how to set up as it would require some kind of anti-diverter valve that would actually stay closed on vacuum but open during near 0psi and stay open until vacuum hits it again. Anybody heard of such thing that would have relatively large ports, like diverter valve?

Maybe here already is such valve in existence that does both functions at the same time?

Thanks.

[Bond]

I was thinking about the exact same setup 2 days ago and new thread pops!! eager to find out as well

[rtl5009]

You're going to need sime beefy lines all venting to atmosphere if you want it to vent with no vacuum under boost. All 3 ports would need to vent to atmosphere directly, no merge ( at least with 5/8" diameter didn't work for me with merge, > 5/8" who knows). The vac helps our cars alot under boost with crank case pressures caused by blow by on high boost applications. You'll never prevent the blow by, you need the vac in boost.

Ask me how I know..... :)

[domantas]

Why dont you simply run all 3 ports (valve covers and crankcase) to y pipe and call it a day.. y pipe is on constant vaccum. Prove me wrong I would appreciate it ;)

[rtl5009]

He doesn't want oil vapors going into the intake tract and into the cylinders, that's why.

[mkemk3]

You're going to need sime beefy lines all venting to atmosphere if you want it to vent with no vacuum under boost. All 3 ports would need to vent to atmosphere directly, no merge ( at least with 5/8" diameter didn't work for me with merge, > 5/8" who knows). The vac helps our cars alot under boost with crank case pressures caused by blow by on high boost applications. You'll never prevent the blow by, you need the vac in boost.

Ask me how I know..... :)

Did you blow the cam cap seal out lol?

[Bond]

Provent --> Y fitting; 1) to Y pipe vacuum 2) vent to atmosphere with a check valve with spring preload ( a ball check valve??)
When there is no excessive pressure it works like stock, when pressure build check valve will open and vent the extra pressure to atm, and at the same time vacuum is still pulling?? would that work

[zillarob]

I dont know of any valves that would divert flow depending on mani pressure, would be sweet though.

Not sure how yours is setup so will apply to stock.

On a stock setup, would require 2 extra check valves.
1st between the pcv valve and ypipe, arrow pointing at pcv valve. Allows pcv valve to regulate crankcase vac without letting blowby to the ypipe.
2nd teed off the other side of the pvc valve, arrow toward atm. This would allow blowby out and seal the system when under vacuum.

[Bond]

OP is not running any PCV, the blow-by oil will be catch inside Mann filter, the air re-entering Y pipe should be of minimum oil vapor.

[rtl5009]

Did you blow the cam cap seal out lol?

Yes lol. I though my turbo blew at first. I was doing a pull and all of a sudden boom huge cloud of white smoke behind the car. I was legit bummed until I pulled over and smoke was billowing out from beneath the hood.

Mine would blow at around 17 psi. I had both heads and block 5/8" hose to collector and then 5/8" vent to air. No dice. Needs vacuum under boost.

[rtl5009]

It makes the biggest mess when the cam caps blow out.

[Bond]

Y pipe vaccum flow rate is not enough to depressurize the onset pressure build up during high boost high revs. does that sound right?

Why dont you simply run all 3 ports (valve covers and crankcase) to y pipe and call it a day.. y pipe is on constant vaccum. Prove me wrong I would appreciate it ;)

[zillarob]

OP is not running any PCV, the blow-by oil will be catch inside Mann filter, the air re-entering Y pipe should be of minimum oil vapor.

He wants to run mani vac, you need to run a pancake valve to regulate vac to the crankcase.

[jibberjive]

Today I started thinking about this a bit more and would like to modify the system to return to y-pipe when there is relative vacuum in the manifold and vent to atmosphere when the car is under boost. This would make PCV system effective during DDing as all the vapors would get burned off, and at the same time it would prevent these blow by products entering intake path during boost to prevent HP loses associated with that.

Why do you want to return to the Y-pipe when there's vacuum in the manifold? Why not simply return to the manifold when there's vacuum in the manifold, via a simple check valve like stock? That line a check valve is sized to flow what the engine is supposed to under those DD-type vacuum situations. Also, regarding venting to the atmosphere rather than Y-pipe vacuum under boost, that's a terrible idea, like rtl5009 said. These cars suffer from an undersized PCV tract that is too small for upgraded power as-is, and removing that one connection is like cutting the PCV's only leg out from under it. That's like putting huge turbos on a stock 2.7t and only installing 2 of each mains 4 bolts to save weight; you want to do what you can to help relieve more of the crankcase pressure, not exacerbate it.

You've got the provent to remove the oil from the air, so don't worry about oil getting into the combustion process (have you checked your Y-pipe and IC's since installing the Provent and it's still sucking oil into the intake tract?). You've got the Provent 200 I assume (as the 400 is physically huge and I can't imagine where you'd stuff it in the cramped 2.7t engine bay. edit: oh yeah, forgot you're an allroad)? If you've got the 200, that adds two more strikes against the proper flow of the blowby gasses, as the provent, though effective at removing entrained oil, is a filter-type separator, which inherently has appreciable pressure drop across the filter media. Also, the 200 is undersized for the power and flow that you're going to be running with your 770's. So your PCV needs all of the help it can get rather than taking away it's main vacuum source.

[domantas]

Y pipe vaccum flow rate is not enough to depressurize the onset pressure build up during high boost high revs. does that sound right?

Completely opposite if i get yor question right. Running only y pipe vaccum would actually give you more suction. Manifold is under pressure when car is under boost therefore you need check valve there. Do you guys really think y pipe is not producing enough vaccum under all conditions? I would assume its least effective while car is at idle but thats it.

[jibberjive]

Completely opposite if i get yor question right. Running only y pipe vaccum would actually give you more suction.

Like you said in the sentence just following this, there is a check valve on the IM connection, so running just y-pipe won't give you and more suction.

[britishturbo]

Completely opposite if i get yor question right. Running only y pipe vaccum would actually give you more suction. Manifold is under pressure when car is under boost therefore you need check valve there. Do you guys really think y pipe is not producing enough vaccum under all conditions? I would assume its least effective while car is at idle but thats it.

At idle there is zero vacuum pre throttle body. Check the MAP sensor in VagCom ;-)

[julex]

Why do you want to return to the Y-pipe when there's vacuum in the manifold? Why not simply return to the manifold when there's vacuum in the manifold, via a simple check valve like stock? That line a check valve is sized to flow what the engine is supposed to under those DD-type vacuum situations. Also, regarding venting to the atmosphere rather than Y-pipe vacuum under boost, that's a terrible idea, like rtl5009 said. These cars suffer from an undersized PCV tract that is too small for upgraded power as-is, and removing that one connection is like cutting the PCV's only leg out from under it. That's like putting huge turbos on a stock 2.7t and only installing 2 of each mains 4 bolts to save weight; you want to do what you can to help relieve more of the crankcase pressure, not exacerbate it.

You've got the provent to remove the oil from the air, so don't worry about oil getting into the combustion process (have you checked your Y-pipe and IC's since installing the Provent and it's still sucking oil into the intake tract?). You've got the Provent 200 I assume (as the 400 is physically huge and I can't imagine where you'd stuff it in the cramped 2.7t engine bay. edit: oh yeah, forgot you're an allroad)? If you've got the 200, that adds two more strikes against the proper flow of the blowby gasses, as the provent, though effective at removing entrained oil, is a filter-type separator, which inherently has appreciable pressure drop across the filter media. Also, the 200 is undersized for the power and flow that you're going to be running with your 770's. So your PCV needs all of the help it can get rather than taking away it's main vacuum source.

I currently have, forget exact size of hose, whatever slips OVER valley and both valve covers PCV ports (I am thinking 3/4" ID) merging in the middle to 1" ID hose going to provent 200. Outlet is 1" going over y-pipe nipple. I am not worried about provent 200 not keeping up with blow by gases under boost, I am ok with it not filtering the gases anymore as it has pressure relief valve built in that diverts them directly to outlet... last resort is oil cap pressure relief valve. System is more than sufficient as is... But.

I know that it is robbing me from some HPs as the spent gas (no oxygen in it!) must be sizable during high boost pulls. This gas is HOT, needs to be compressed by turbos and yet it contributes ZERO to making power, it is actually a lost opportunity for legit oxygen to enter the system in its place and make power.

So that's why I am looking for ideas here...If a switch of some sorts can be installed to divert gases somewhere else, then a road draft tube can be installed to provide some vacuum.

Edit: Just checked, provent will actually relieve the pressure by venting outside, not directly to outlet.

[zillarob]

I see now.

Provent exit through hose with check valve on end, arrows to atm.
Tee off that hose, through dv, to ypipe. Vac nipple to mani.

Under vac, check valve will seal the system, mani vac will open the dv, and flow to ypipe.
Under boost, dv will be closed, flow through check valve.

[jibberjive]

If you don't care about filtering the stuff and are fine with letting it bypass, maybe just set the intake manifold leg as per stock with the check valve, and have the other side hooked up to a vacuum pump that is connected to a solid state relay that is turned on by a hobbs switch. That way the vacuum pump is boost activated, and all the rest is setup as per stock.

[julex]

I like zillarob's idea. It should work ok except that I would need a properly sized check valve so that it can flow enough during wot.

[jibberjive]

Why would you go to the Y-pipe instead of the intake manifold? With the throttle blade close to closed and the huge volume of the intake tract right next to atmosphere, you won't pull near the vacuum that it supposed to at idle/low revs, like you would if you just hooked it up to the intake mani for that part of the vacuum source. What benefit do you see from going to the Y pipe and deleting the IM connection?

[julex]

Why would you go to the Y-pipe instead of the intake manifold? With the throttle blade close to closed and the huge volume of the intake tract right next to atmosphere, you won't pull near the vacuum that it supposed to at idle/low revs, like you would if you just hooked it up to the intake mani for that part of the vacuum source. What benefit do you see from going to the Y pipe and deleting the IM connection?

I realize that my setup is wrong on the idle/low load part by not incorporating IM vacuum source, consider it "fixed" for the purpose of this discussion.

[jibberjive]

Ah, zillarob's last post said the y-pipe bit, so when you said you were headed that direction, I thought y-pipe part as well. I'm curious to see how the no vacuum source (in boost) works out for you.

[Monty23]

Would it be possible to plumb the catch can to a downpipe and draw the vacuum from the exhaust? That would solve all the above issues....

edit - I am not sure if the exhaust is actually under vacuum though

[julex]

So I spent few minutes drawing it and please comment if this would work or not....

[julex]

Would it be possible to plumb the catch can to a downpipe and draw the vacuum from the exhaust? That would solve all the above issues....

edit - I am not sure if the exhaust is actually under vacuum though

I heard of people talking about that but I don't think it is feasible without so much work that is defeats the purpose imho. Plus you'd have extreme temps to deal with which would probably prove it unreliable.

[julex]

Ah, zillarob's last post said the y-pipe bit, so when you said you were headed that direction, I thought y-pipe part as well. I'm curious to see how the no vacuum source (in boost) works out for you.

Lots of people vent to atmosphere without any provisions for vacuum and are fine. I am planning to eventually use a draft tube though which will provide some level of vacuum, the faster car goes the more of it.

Anyway, I will do some pulls with y-pipe sucking and venting to atm to see if there is any performance difference. This test will determine what I do next, if anything at all.

[034Motorsport]

I had no issues venting to atmosphere on my STK car with 3/4" silicone merging into a single can from the crank case and the valve covers. No blown cam caps or anything like that.

This will largely depend on how your motor is built, but I wouldn't expect you to have issues venting to atmosphere through normal 3/4" lines unless you have some gigantic ring gap and a ton of blow by, and then you have bigger problems.

[Monty23]

I had no issues venting to atmosphere on my STK car with 3/4" silicone merging into a single can from the crank case and the valve covers. No blown cam caps or anything like that.

This will largely depend on how your motor is built, but I wouldn't expect you to have issues venting to atmosphere through normal 3/4" lines unless you have some gigantic ring gap and a ton of blow by, and then you have bigger problems.

Did you run the vented oil filler cap? p/n: 078 103 485 F

[julex]

I had no issues venting to atmosphere on my STK car with 3/4" silicone merging into a single can from the crank case and the valve covers. No blown cam caps or anything like that.

This will largely depend on how your motor is built, but I wouldn't expect you to have issues venting to atmosphere through normal 3/4" lines unless you have some gigantic ring gap and a ton of blow by, and then you have bigger problems.

So it was an open system that replaced stock PCV or some hybrid that still used intake manifold vacuum and check valves?

[bobkatkat]

So I spent few minutes drawing it and please comment if this would work or not....

how is this different to your current setup with the Provent?

[julex]

how is this different to your current setup with the Provent?

There is no IM or Atm connection at all. Return hose goes to Y-pipe without any check valves involved - works fine so far... Keep in mind provent is very efficient at filtering vapors.

[034Motorsport]

Did you run the vented oil filler cap? p/n: 078 103 485 F

So it was an open system that replaced stock PCV or some hybrid that still used intake manifold vacuum and check valves?

Vent to atmosphere. Meaning the crankcase and the two valve cover breathers merged into a single silicone line that went to a catchcan, and vented to atmosphere through a small filter. That's it. No check valves, no recirculation back into the intake.

It smells bad at idle and you're engine bay will always be a bit oily. But it certainly functions just fine, as the many miles and 1/4 mile runs proved. With a catless exhaust and a 6262 turbo, odd smells and such are pretty normal. Never affected A/C.

I used the stock oil cap. I also paid a lot of attention to ensure there were absolutely no valleys in my hoses; all gasses were able to continuously rise.

Provent is a very good catch can and if I was going to recirculate, that is what I would use.

[rnagy86]

Vent to atmosphere. Meaning the crankcase and the two valve cover breathers merged into a single silicone line that went to a catchcan, and vented to atmosphere through a small filter. That's it. No check valves, no recirculation back into the intake.

It smells bad at idle and you're engine bay will always be a bit oily. But it certainly functions just fine, as the many miles and 1/4 mile runs proved. With a catless exhaust and a 6262 turbo, odd smells and such are pretty normal. Never affected A/C.

I used the stock oil cap. I also paid a lot of attention to ensure there were absolutely no valleys in my hoses; all gasses were able to continuously rise.

Provent is a very good catch can and if I was going to recirculate, that is what I would use.

I can only second venting to atmosphere. I just basically have the exit hose routed down below the car, which has made the bad smell go away 90%. There is still some at idle but it's hardly noticable. I decided to go this way after I have destroyed _2_ check valves in my spider hose in the period of 5 months. I could have switched to metal valves but meh, it's still a system that's prone to fail.

[Meow]

I currently have mann oil separator system installed on my 2.7 which replaces stock PCV system and has return to Y-pipe for clean non-smelly car. The system also drains separated oil back to oil pan.

Today I started thinking about this a bit more and would like to modify the system to return to y-pipe when there is relative vacuum in the manifold and vent to atmosphere when the car is under boost. This would make PCV system effective during DDing as all the vapors would get burned off, and at the same time it would prevent these blow by products entering intake path during boost to prevent HP loses associated with that.

What do you consider blowby product? The oil or the air? There is almost no notable loss in power if you have a catch can to collect the oil in the blowby. The key is the location you put the catch can. It needs to be below the tap into be y pipe and it needs to be in a cold spot. Preferably other side of the firewall or far away from the engine. This condenses any oil vapors before entering the intake. And even then... If vapors did enter it won't hardly hurt the performance at all.

The best system, I think, involved exhaust savaging. But that gets far more complicated. A cheap and simple catch can should be employed to remove vapors and that's it.

[zillarob]

So I spent few minutes drawing it and please comment if this would work or not....

Keep in mind, if you run im vac, you will prob need the pancake or some other way of regulating the vac to the crankcase.

[bobkatkat]

There is no IM or Atm connection at all. Return hose goes to Y-pipe without any check valves involved - works fine so far... Keep in mind provent is very efficient at filtering vapors.

Where do you have your Provent 200 mounted? Looks like a fairly large body from the specs.

[domantas]

Why would you go to the Y-pipe instead of the intake manifold? With the throttle blade close to closed and the huge volume of the intake tract right next to atmosphere, you won't pull near the vacuum that it supposed to at idle/low revs, like you would if you just hooked it up to the intake mani for that part of the vacuum source. What benefit do you see from going to the Y pipe and deleting the IM connection?

Ssimplicity. Clean and simple design. Many import guys di it (including me). Im not trying to prqoof anything here or argue but i want a prooven explanation why would yqou want big amounts of vaccum at idle/low thrtl. I need to be convined and if so i need to hook up my manifold then ;)

Edit* i just read 034 post ha... talking about no IM vaccum. Im sticking to my setup, prooven, simple.

[Meow]

Where do you have your Provent 200 mounted? Looks like a fairly large body from the specs.

+1 on that. Mount it low and cold. Make sure it's collecting at the lowest spot in all your hoses and make the air climb back up to the y pipe.

Sounds to me like your current setup is great.