Valve Cover/PCV Confirmation/Question

martymil

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A 2 port really can/cant as you will be restricting flow.

A three port would be mutch better 2 going in and 1 going out with a split for flapper and PCV valve to control flow.
 

doublespaces

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A 2 port really can/cant as you will be restricting flow.

A three port would be mutch better 2 going in and 1 going out with a split for flapper and PCV valve to control flow.

Not sure I follow, mind drawing a diagram of your setup?
 

martymil

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Here you go a 3 and 4 port design that uses a single catch can which makes servicing easy and simple and keeping the cost right down whilst externalizing the whole PCV system away from the stock or aftermarket rocker cover and not restricting flow.
 

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martymil

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You dont need two ports really to vent the catch can as only one system is working at any one time so a 3 port would work very well too but
a 4 port would be much easier to adapt as both systems have very different line sizing but with the right adapters it could be done.

This type of setup has greater benefits than a two catch can setup, two can setup only has one line working at any one time venting the rocker cover.

It might be an overkill but I much rather a setup like this.
 
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martymil

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You could easily get the same benefits with a two can system but you would have to run a balance pipe between the outlets on both cans.

The only one i know that would work/look nice is the VTT two can setup and staying very compact.

Having two lines feeding the catch can/s has less tendency of pulling oil into the catch can/s so you don't have to clean it/them as often
unlike the current setups.
 

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Coupes66

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Thanks Doublespaces for your detailed explanation of the pcv system. I have always been mystified by why forum members made all of these changes to the system. I can understand those running a ST need to do it but those with twins I am not so sure. I have had my car for 10 yrs and have only run a oem system apart from a RB pcv. I have done 100 runs at the drags, 70,000 kms on the engine, 28 psi boost and achieved a 10.7s run without any issues with this system. Whether I have been just lucky or my system is getting enough vacuum via the connection to the rear VTT inlet hose to reduce the crank case pressure, I am not sure. The main thing is that it appears to be working. Back 40 yrs ago when I use to run small block chevy engines at the drags, I used a system where a venturi pipe with a one way valve was welded into the outlets of the extractors. A hose ran from this valve up to the valve covers. The speed of the exhaust gases passing the ventuis would create the vacuum that depressurised the crank case. I don't know if anything like this could be designed for the N54 engine.
 
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martymil

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No one saying you cant run an oem system with an rb valve and works quite well.

The problem is the stock valve covers crack and leak, valves get dirty and maintenance gets costly.

The whole idea to run a properly setup catch can system is to keep oil away from the valves and intake track which will costs you octane and
performance loss by allowing oil to pass through the head ports unless you externalize the PCV.

Having the crankcase vented to the exhaust could possibly cause smoke and you would have to vta the rocker cover so it doesn't cause too much vacuum
in the crankcase making the whole system illegal for street use.
 

twinturbos

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Since VTT was out of stock I bought an M18 valve cover. I really hope the fit is good. My motor is on an engine stand so I should be able to see how the fitment is. I still do not understand what I will need to fix the PCV problem.
Mine is fine. You have to re-torque it 2-3 times as the material works while you torque it.
 

Coupes66

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No one saying you cant run an oem system with an rb valve and works quite well.

The problem is the stock valve covers crack and leak, valves get dirty and maintenance gets costly.

The whole idea to run a properly setup catch can system is to keep oil away from the valves and intake track which will costs you octane and
performance loss by allowing oil to pass through the head ports unless you externalize the PCV.

Having the crankcase vented to the exhaust could possibly cause smoke and you would have to vta the rocker cover so it doesn't cause too much vacuum
in the crankcase making the whole system illegal for street use.

I didn't have to VTA from the rocker covers as the hoses were connected to them. That was the location from which the vacuum was subjected to. The photo below shows what I am talking about.
 

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doublespaces

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You dont need two ports really to vent the catch can as only one system is working at any one time so a 3 port would work very well too but
a 4 port would be much easier to adapt as both systems have very different line sizing but with the right adapters it could be done.
Well, if you go that far, then a two port can would suffice, it just won't have the maximum flow capability.

The question: Is venting from a single VC port enough flow? And this is one of a few questions I wanted to answer with my other thread: https://bmw.spoolstreet.com/threads/measuring-crank-case-pressure.6176/

Some people don't understand why anyone would care to have measurements, but there are a variety of measurements that I've not seen so I'm going to try and record some when I have time. I can vent from 1 to 3 ports at a time, so I'm curious which works best for me.
 

martymil

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I didn't have to VTA from the rocker covers as the hoses were connected to them. That was the location from which the vacuum was subjected to. The photo below shows what I am talking about.


I'm saying you would have to vta our rocker cover to make something like this work on our cars or supply a fresh filtered source of air not to cause
seal issues causing to much vacuum in the crankcase as the exhaust will be pulling lots of gases and it still wont be legal because of the oil vapour entering the exhaust as it has to be recycled.
 

martymil

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Well, if you go that far, then a two port can would suffice, it just won't have the maximum flow capability.

The question: Is venting from a single VC port enough flow? And this is one of a few questions I wanted to answer with my other thread: https://bmw.spoolstreet.com/threads/measuring-crank-case-pressure.6176/

Some people don't understand why anyone would care to have measurements, but there are a variety of measurements that I've not seen so I'm going to try and record some when I have time. I can vent from 1 to 3 ports at a time, so I'm curious which works best for me.


Not saying a 2 port wont work but could possibly restrict airflow in high demand circumstances.

Test away but for the cost of testing equipment you could have brought a 3 port catch can and sold off the rest and actually made some money out of it.

On our stock valve cover its only one port that works at anyone time but that was designed for stock boost, if you double or triple the boost you need
to increase the flow too.
 

doublespaces

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Not saying a 2 port wont work but could possibly restrict airflow in high demand circumstances.

Test away but for the cost of testing equipment you could have brought a 3 port catch can and sold off the rest and actually made some money out of it.

On our stock valve cover its only one port that works at anyone time but that was designed for stock boost, if you double or triple the boost you need
to increase the flow too.

Oh, its never been about the money, not for something like this anyway. Otherwise I need to sit down and have a Jesus moment with myself; Its just about curiosity of knowledge and having something tangible to associate with the reasoning. I have three catch cans right now, two on back and one going on the front, so hopefully I'm able to producing something interesting.
 
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fmorelli

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The whole idea to run a properly setup catch can system is to keep oil away from the valves and intake track which will costs you octane and
performance loss
by allowing oil to pass through the head ports unless you externalize the PCV.
I agree with everything @martymil has said. But IMHO the much larger cost is the hundreds of threads and thousands of posts around misfire 2/5, vacuum problems, CEL lights and various codes which indirectly result from vacuum leaks, blah blah blah blah blah ... people consume tremendous amounts of hours and frustration with cars that don't run quite right and I'm convinced a fair bit of it has to do with the issues being discussed here.

Filippo
 
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derekgates

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I will oblige to respond although I have my own opinions on all of this. The confusion you are experiencing is unfortunate because its kind of unavoidable at this point.

When they say 'external pcv' what they mean is they are moving the cyclonic oil separators to the outside as you know. To do this, all that voodoo under the valvecover gets bypassed which is why aftermarket vc's don't need to have it. Its also the reason that plugging head ports is mandatory when you run an after market VC, because there is no PCV valve on that pathway to block boost from entering the crank case.

So as a very short review, in a normal situation when you're idling, the minimal blowby existing in the crank case is being sucked out by going past the pcv valve, and into the individual head port channels, into the head etc. This is the 'low side' operation. During boost, that process attempts to reverse, it goes up the individual head port channels, but the pcv valve blocks it from going any further so you don't pressurize the crank case with your intake charge.

When this gets 'externalized' what happens is instead of crank case blow by being sucked through the pcv valve toward those head port channels, the external PCV valve redirects that flow out a barb on the back of the VC. That goes to your low side can, and then from there it goes to the Throttle body back into the manifold, back into the engine. So instead of going through the head ports, it takes a long way around essentially and that is the externalization.

So when you run an aftermarket VC, it is assumed you are doing this already. By that I mean, plugging the head ports and sucking crank case blowby from one of those VC ports, into the tb etc. There is no magic inside the VC that requires there to be any sort of separation or compartments etc. The high/low side concept is nothing more than a "how does crank case ventilate from the VC" question. Does it get sucked into the engine via the throttle body through one port or does it get pushed out of another.




Do not confuse VTA with PCV delete. You Venting To Atmosphere just means the crank case fumes are being expelled to the open air and not being re-ingested somewhere, except maybe your lungs. People tend to throw these terms around as they usually are done together but it isn't so. You can VTA the high side on a PCV setup, in fact I think most single turbo people do as there isn't a good place to recirculate it.

I can't see for sure, but if I were to guess, he's got a dual can setup from VTT. The hose on the VC closer to the firewall goes to one can and then outlets downward with a one way check valve going to the throttlebody or a port on the intake manifold. This is his 'low side'. He also has a vacuum break on the front of the VC, this acts as his flapper so he doesn't over-vacuum the crank case and cause the seal howling issue.

The other port off the vc runs to the other catch can and is VTA off that filter there. So this is a good example of a 'PCV setup' which is also VTA.




If you have a dual can setup now with external PCV, the only thing changing is the fittings going to the valve cover and ensuring your head ports are plugged. So instead of the External PCV valve, the one with the nipple, you'd be replacing that with a normal 10AN fitting with a barb on it or whatever your hoses need. And if you've got a flapper valve hooked up to your other can, you'd have to make some fittings to convert 10AN to some 3/4 barb so you can put a hose over the flapper and then from the flapper run to your other catch can and then back into the inlet or VTA.

If you don't want to do hose conversion on the flapper, you can just run the 10AN from the VC directly to the catch can and VTA/Inlet and then you'll need to install the vacuum break on a third port of the VC.

Great info, for sure. I bookmarked this.

NA PCV systems are pretty clear to me.

Our engine makes my head spin a little bit and I am never sure I am cleaning the air stream with the setups I envision. The loop back seems fuzzy to me. I do not want VTA unless on the track... I brought that up since I see many cars and recommendations from VTT with their breather filters on the top.

This was helpful. Your breakdown of the routing is great for me! I am wanting to keep using my BMS&Mishimoto cans as they weren't free... Sounds like I can still achieve that.

Hopefully this helped others as well. :)

You can also run a 4 port catch can system and simplify the whole setup.

I'm testing this atm and is working perfectly.

Just figuring out options to make the whole setup budget orientated

It's basically the whole PCV system externalized in an easy one can setup that can be adapted to any vc setup you have and easily transferable
from a stock vc to any aftermarket setup when funds allow.

I just don't know why no one came up with this sooner.

Ah, nice. Radium or similar? Are you using the vacuum break like described above?

[EDIT] Crap, saw your other posts in this thread. haha
 

martymil

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With any of the setups I illustrated are all plumbed back for recirculation to keep things legal to meet emission standards.

I do not use or recommend VTA under any circumstance by choice of my own, any one can do as they wish.

You can use any catch can system you like as I have no preference, in the end they all do the exact same thing but some do it
better than others what sets them apart.

I'm doing one right now for a customer using the VTT twin can setup and using the twin setup I illustrated earlier.
 
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doublespaces

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Great info, for sure. I bookmarked this.

NA PCV systems are pretty clear to me.

Our engine makes my head spin a little bit and I am never sure I am cleaning the air stream with the setups I envision. The loop back seems fuzzy to me. I do not want VTA unless on the track... I brought that up since I see many cars and recommendations from VTT with their breather filters on the top.

This was helpful. Your breakdown of the routing is great for me! I am wanting to keep using my BMS&Mishimoto cans as they weren't free... Sounds like I can still achieve that

I had the same question as you, I pictured there being special compartments inside that were pressurized under different circumstances and if you removed the guts of the valve cover it all gets thrown off.

The reality is those compartments don't really need to exist when the head ports are plugged, and the function of how your crank case vents is controlled by the pressure in the crankcase.

If there is positive pressure, one valve is closed and the other is open. The closed valve is shut from the opposite side as boost is trying to enter.

If there is negative pressure, flapper is closed but flowing as a 'restrictor, and pcv valve is open, air will enter one valve and exit the other valve(into the throttle body connection).

It's an if/else scenario dictated by the crank case pressure and controlled by the valves. The internal structure of the stock VC is actually irrelevant. And the reason is: this is just an engine like any other engine, despite people trying to make it more than this. Tons of bandaids have been applied and hence all the confusion we have.
 
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martymil

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I had the same question as you, I pictured there being special compartments inside that were pressurized under different circumstances and if you removed the guts of the valve cover it all gets thrown off.

The reality is those compartments don't really need to exist when the head ports are plugged, and the function of how your crank case vents is controlled by the pressure in the crankcase.

If there is positive pressure, one valve is closed and the other is open. The closed valve is shut from the opposite side as boost is trying to enter.

If there is negative pressure, both valves are open, air will enter one valve and exit the other valve(into the throttle body connection).

It's an if/else scenario dictated by the crank case pressure and controlled by the valves. The internal structure of the stock VC is actually irrelevant. And the reason is: this is just an engine like any other engine, despite people trying to make it more than this. Tons of bandaids have been applied and hence all the confusion we have.


Most catch cans have some kind of oil separator in them to filter oil from the gases.

You don't have to plug the head ports on a stock vc all you have to do is use the proper connection to block the vc vacuum/ boost ports
supplied by most manufacturers now.


Even on an aftermarket cover you don't have to block them as the vc seal will do this up to a point, but it is strongly recommended that you do block them
to stop possible boost/vacuum leaks.

Nope the flapper valve is spring loaded so when it sees no pressure it will be shut.

The flapper and PCV work in opposite ways so there is no way that both can be open at the same time.
 

doublespaces

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You don't have to plug the head ports on a stock vc all you have to do is use the proper connection to block the vc vacuum/ boost ports
supplied by most manufacturers now.


I also have this part, two of them but trying to explain it in the same sentence as blocking head ports which is a universal solution would be adding to the confusion. This part doesn't work with an aftermarket valve cover, so while it may serve most of the same purpose as blocking head ports, its a secondary subject to understanding the PCV system. What you're saying doesn't make what I said not true, when the head ports are plugged none of that stuff in there matters; the things related to cyclonic oil separators or passages, channels, compartments, its all irrelevant.

Even on an aftermarket cover you don't have to block them as the vc seal will do this up to a point, but it is strongly recommended that you do block them
to stop possible boost/vacuum leaks.

On a setup with proper PCV valves, no technically you don't. People with PCV delete do of course but again, we depend on more valves, more configuration, more confusion and more threads posted like this. Just block them for goodness sake, it isn't a hard to understand process. If people were going to understand it, they would have after ten years. They don't because people make it more complicated than it is. If they don't want to do the recommended method then they are on their own IMO.

The flapper and PCV work in opposite ways so there is no way that both can be open at the same time.

This is a mis-speak on my part, I've edited my response. the flapper is 'restricted' and the pcv is open, however air is still entering the flapper and exiting the pcv, which was the point I was trying to make.
 
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