Fundamental PCV systems

[fmorelli]

So if you wish to argue about it, please start your own thread. Why is PCV operation so hard for people to wrap their head around?

I agree with Chris. Two pages into a VTT vacuum relief valve produce release promo thread ... the intention is not to side tract the promo. But 37 posts into the thread, @Chris@VargasTurboTech asks the fundamental question. So shall we discuss it here and maybe create some clarity? Chris I would assume, if you can figure out the answer to your question, this would help you generate more sales? I know I'd like to understand as if improvements can be made to my PCV system I'd like to do so. I assume most people fall somewhere in between you and your question and me.

I'll take a first crack at your question. If you look at post #9 on the VTT relief valve promo thread, I laid out what the fundamental questions from my perspective. Note my use of the word, fundamental. Note I also stated up front that I had no problem saying I'm ignorant or even not smart enough to get it. I have a thick skin, so not getting an answer to my four point question was cool; I was not surprised given I was watching others not even be able to get yes/no answers from one another on questions (I'm not say from you ... from the multiple people in the discussion) - that tells me, and I knew this immediately, that folks are not on the same page.

I suspect I, like others, are caught up in relative understandings of relative parts of a turbo PCV system.

1. how a turbo motor PCV system works - fundamental attributes, desired controls, solution architectures.
2. the BMW specific solution architecture.
3. modified performance architectures. And the corresponding what/why/how's of these.

I addressed Chris in the first paragraph but to be clear, I'm not asking him to explain all this! I'm just pointing out my view of the crux of the problem between his very good question (quoted above) and my abbreviated 4 point question set in the aforementioned promo thread post #9.

And it seems like I'm not alone in not getting it - there are disagreements and different explanations by people here that I know are more clueful than. I then infer there are a shit ton of people silent that have no freaking idea either. In the Facebook group, the conversation doesn't even get as deep as in the promo thread here ... but the confusion is equally obvious. So selfishly speaking, I'd love to see a comprehensive discussion on this topic. And I would hope that the result is that more people would get educated, build better functioning PCV systems for their modified cars, and buy the products from our vendors which support that quest.

I'm sure someone else can guide this conversation better than I can. That said - in my 3 questions above, maybe a few good articles on the web would give us fundamentals to answer #1? Likely, #2 & #3 are discussion.

Win win?

Filippo

 

[fmorelli]

Reserved.

 

[martymil]

The ideal system is a fully closed system at idle with a proper metered vacuum and a fully open system with no back pressure on full throttle so the crank case can breathe.

 

[BOosted 335i]

I'll give it a shot,
I have a high and low side cc setup.my lowside has vtt checkvalve to prevent boost underload,thats basic, now the high side I have the stock BMW flapper to cc then vta.
With that said would it be better to just get rid of the BMW stock flapper and put a check valve/ball units place and vta and call it a day right?Because right now under vac I'm probably losing some from the high side stock flapper due to the little hole correct?

 

[martymil]

The ideal system is the one I drawn up in the other thread, you can do other ways guys that's the best way or if using a stock rocker cover put the relief valve on the vacuum line but you must use a non metered unlike the oem flapper valve on the high side or check valve from VTT.

 

[The Convert]

I'll give it a shot,
I have a high and low side cc setup.my lowside has vtt checkvalve to prevent boost underload,thats basic, now the high side I have the stock BMW flapper to cc then vta.
With that said would it be better to just get rid of the BMW stock flapper and put a check valve/ball units place and vta and call it a day right?Because right now under vac I'm probably losing some from the high side stock flapper due to the little hole correct?

If you replace the high side flapper with a check valve, you have to add the new vacuum break VTT is selling, otherwise you will pull vacuum past the seals and have a bad day.

 

[Kommodore]

Right now I am running full VTA, with the head ports blocked, and no flapper valve.

• The orifice where the flapper valve was uses a 10an fitting that routes a line to a catch can.
• The port on the front of the head which used a large plug also has a 10an fitting that also routes to the same catch can.
• The catch can vents out the top, and a 1" line with a filter on the end of it is routed all the way back to where my gearbox is.

With this configuration I get more fumes than I would like. So, I am thinking of re-configuring this using a Mann Provent 200. I'd like to use the flapper orifice to feed the Provent. And, I would like to use a fitting where the dip stick hole is near the starter to drain oil back into the motor. Then, the out vent on the provent I would like to route back to probably the front turbo intake.

I don't know if this contributes to this discussion, but I don't feel like the intake is going to pull enough vacuum to warrant something like the VTT valve. The part of this that I think is relevant to this overall discussion, is if the flapper orifice was large enough for the stock system, is it still large enough on a modified engine for venting crank case pressure? Otherwise in my case I would end up having to run two provents. The current catch can has a very large 1" opening in the top of it so I didn't have any concerns feeding two lines to it. But, I wonder if it is overkill.

 

[Chris@VargasTurboTech]

This diagram is ideal, just add a high side check valve and Vaccum relief, and you are about as good as you are going to get without a real vacuum pump.

 

[The Convert]

This diagram is ideal, just add a high side check valve and Vaccum relief, and you are about as good as you are going to get without a real vacuum pump.

I have to disagree, but only on the placement of the low side valve. I would always put it between the VC and cats he can to prevent any chance of pressurizing the can and blowing oil out of it. And yes, I realize the chances of that are very low.

 

[martymil]

Its the other way around you put the check valve between manifold and catch can because if you put the pvc between the catch can and valve cover the catch can will be pressurised by the boost from the manifold

 

[Chris@VargasTurboTech]

I have to disagree, but only on the placement of the low side valve. I would always put it between the VC and cats he can to prevent any chance of pressurizing the can and blowing oil out of it. And yes, I realize the chances of that are very low.

What are you saying is completely backward. If you move the check valve to the other side of the can that is EXACTLY what you are doing. Putting full manifold boost into the catch can. Think about what you are saying. You want to take the check valve that is stopping boost, and move it after the can, and before the vc. So now the boost is going through the can before it reaches the check valve. Very dangerous. Catch cans are never designed to operate under boost. PCV threads are basically the same thing as what oil should I run threads. It's going to be 15 pages of opinions, and people arguing over what's best.. ‍

 

[fmorelli]

More evidence of the obvious. https://www.facebook.com/groups/n5xenthusiasts/permalink/2469261429791574/

I made a tongue and cheek, somewhat prophetic comment, at the beginning of that thread, that at 100 posts I'd come back and read it. It's a 73 comments and counting.

Filippo

 

[NoGuru]

Subbing, because I have no freaking clue about this stuff.

 

[The Convert]

What are you saying is completely backward. If you move the check valve to the other side of the can that is EXACTLY what you are doing. Putting full manifold boost into the catch can. Think about what you are saying. You want to take the check valve that is stopping boost, and move it after the can, and before the vc. So now the boost is going through the can before it reaches the check valve. Very dangerous. Catch cans are never designed to operate under boost. PCV threads are basically the same thing as what oil should I run threads. It's going to be 15 pages of opinions, and people arguing over what's best.. ‍

Just relooked at the diagram. I missed that bit and do agree with you.

 

[fmorelli]

So trying to make sense of my setup.

Feel free to comment on anything here. That said, I'm looking to remove the high-side flapper, install a flapper delete, install a high-side check valve between the VC and the BMS catch can, and install the new relief valve. Benefit of this is that my PCV system is locked and loaded with a safety and no vacuum-related VC or seal issues.

Now, I'm not looking to replace my VC. I'm not looking to drill holes in my VC either as then I'm also drilling my engine cover. I want the relief valve on the VC side of any valve. Running the current BMS system, I don't see an obvious way to keep that and do a reasonably clean plumbing job. Cart before the horse problems - if I install a VTT flapper delete --> VTT check valve --> 90º 110AN to barb, I've forced the relief valve to be installed in the valve cover. If I run the VTT flapper delete-> 90º -10AN fitting-> some kind of T fitting with -10ORB on top with the relief valve on the top, and then heater hose off the other side ... I'm hanging a bunch of crap off the backside of the valve cover which is bad mojo.

I could replace the BMW high side catch can, but VTT web site incorrectly states "N54" bracket - it's not. It's a 135i/335i bracket. Z4 N54 runs a circular bar so those mounts don't work. I currently have a custom mount fabricated for the BMS system. I'd rather not make a further life's work out of this so I was hoping to figure out how to work this in, without completely changing my high-side system out, or drilling holes into my VC.

I know it's clear as mud.

Filippo

 

[fmorelli]

Subbing, because I have no freaking clue about this stuff.

Gee whiz ... I'm surprised!

FIlippo

 

[Chris@VargasTurboTech]

I

So trying to make sense of my setup.

View attachment 28672

Feel free to comment on anything here. That said, I'm looking to remove the high-side flapper, install a flapper delete, install a high-side check valve between the VC and the BMS catch can, and install the new relief valve. Benefit of this is that my PCV system is locked and loaded with a safety and no vacuum-related VC or seal issues.

Now, I'm not looking to replace my VC. I'm not looking to drill holes in my VC either as then I'm also drilling my engine cover. I want the relief valve on the VC side of any valve. Running the current BMS system, I don't see an obvious way to keep that and do a reasonably clean plumbing job. Cart before the horse problems - if I install a VTT flapper delete --> VTT check valve --> 90º 110AN to barb, I've forced the relief valve to be installed in the valve cover. If I run the VTT flapper delete-> 90º -10AN fitting-> some kind of T fitting with -10ORB on top with the relief valve on the top, and then heater hose off the other side ... I'm hanging a bunch of crap off the backside of the valve cover which is bad mojo.

I could replace the BMW high side catch can, but VTT web site incorrectly states "N54" bracket - it's not. It's a 135i/335i bracket. Z4 N54 runs a circular bar so those mounts don't work. I currently have a custom mount fabricated for the BMS system. I'd rather not make a further life's work out of this so I was hoping to figure out how to work this in, without completely changing my high-side system out, or drilling holes into my VC.

I know it's clear as mud.

Filippo

I see issues with that set up the first being why a 50-micron filter? PCV systems are all about VENTING. You want to vent as much possible, that is the entire purpose of a PCV system. POSITIVE CRANKCASE VENTILATION. Not positive crankcase filtering. Adding a filter as small as 50 microns is simply restricting flow, and is the opposite of what you want. This is why most cans, have baffling to just knock the liquid from the vapor, there is no need to filter anything down to 50 microns. As for the bracket, we offer a universal bracket that can be mounted anywhere you want to add a couple of holes, simply choose universal bracket.

 

[fmorelli]

That's an interesting observation. Is it as black and white as venting or not? For instance using the same logic, an engine air intake would not have an air filter since it is all about getting air in to the engine. Yet the constraint is that the unwanted particulate in the air necessitates a filter to mitigate. I would surmise that the PCV case we have the same analog - to remove oil suspended in the airflow. Mishimoto, sells an N54 PCV kit with a 50-micron catch can: https://www.mishimoto.com/bmw-n54-baffled-oil-catch-can-kit-07.html. VAC Motorsports sells the same thing, and they are in the engine-building business. I'm just pointing out that there are two reputable companies that are using a 50-micron solution to vent the PCV and capture the oil suspension in the vented air. I'm not implying it is right or wrong, just that it is unclear from credible references what the underlying trade-offs are.

On the low side this is a noteworthy discussion since dragging oil into the intake is the devil. I cannot believe how much smoother my car runs after a 30k mile walnut blast that probably should have been done at 20k. Do you have a different view or solution to minimize oil recirc on the low-side of the system into the intake? I even took pains on my setup to install the PCV feed at the bottom-most location of the intake manifold in hopes of have oil drop to the bottom of the manifold (as opposed to rise and lift into the intake runners - yes wishful thinking). The devil we are dealing with is a DI system with a PCV system that wreaks havoc on the intake tract of these cars, which once used to be washed down by fuel injectors.

Good to know there is a universal bracket - I like the VTT modular offerings. When we build the new inlet setup on my car it looks like I may consider a redo of my whole PCV system then. Thanks for your feedback - @Chris@VargasTurboTech, let me know if you have thoughts relative to my response above.

Filippo

 

[The Convert]

That's an interesting observation. Is it as black and white as venting or not? For instance using the same logic, an engine air intake would not have an air filter since it is all about getting air in to the engine. Yet the constraint is that the unwanted particulate in the air necessitates a filter to mitigate. I would surmise that the PCV case we have the same analog - to remove oil suspended in the airflow. Mishimoto, sells an N54 PCV kit with a 50-micron catch can: https://www.mishimoto.com/bmw-n54-baffled-oil-catch-can-kit-07.html. VAC Motorsports sells the same thing, and they are in the engine-building business. I'm just pointing out that there are two reputable companies that are using a 50-micron solution to vent the PCV and capture the oil suspension in the vented air. I'm not implying it is right or wrong, just that it is unclear from credible references what the underlying trade-offs are.

On the low side this is a noteworthy discussion since dragging oil into the intake is the devil. I cannot believe how much smoother my car runs after a 30k mile walnut blast that probably should have been done at 20k. Do you have a different view or solution to minimize oil recirc on the low-side of the system into the intake? I even took pains on my setup to install the PCV feed at the bottom-most location of the intake manifold in hopes of have oil drop to the bottom of the manifold (as opposed to rise and lift into the intake runners - yes wishful thinking). The devil we are dealing with is a DI system with a PCV system that wreaks havoc on the intake tract of these cars, which once used to be washed down by fuel injectors.

Good to know there is a universal bracket - I like the VTT modular offerings. When we build the new inlet setup on my car it looks like I may consider a redo of my whole PCV system then. Thanks for your feedback - @Chris@VargasTurboTech, let me know if you have thoughts relative to my response above.

Filippo

2 things.

I don’t the air filter is the best comparison since the surface area of the filter is usually designed so that the combination of the restrictiveness of the filter is paired with the overall size of the filter so that the filter is capable of flowing the mass flow that the engine needs. Whether or not a 50 micron filter at whatever overall size it is in the pcv system causes a restriction is beyond me though. I would say that as long as it has enough holes for the required flow rate, the hole size should be irrelevant as far as restriction goes.

I would still like to see a good pi control and small injectors specifically for keeping the valves clean like the Toyota engines.

 

[Chris@VargasTurboTech]

I personally would never add anything to a PCV that filters down that small, it's not needed, and its a restriction.