Yes but do you have vacuum when you connect an OCC e.g. the mishimoto one?
RB external PCV setup
- Thread starter TurboMike
- Start date
Rob@RBTurbo
Lieutenant
Just out of curiosity, was an exhaust Venturi ever considered as the source of negative pressure?
I'm considering this kit, anyone recommend any additional parts outside of what can be purchased directly from the site kit A?
I installed Rob's kit when it first came out (many months ago) and have a catch can in the loop. My catch can collects a lot of oil, enough that I have to drain it within my 5k mile oil change cycle to keep it from overfilling. One time I noticed the car smoking at a traffic light and the can had overfilled. While my experience may not be typical, my can collects clean and moisture free oil and I could pour it back into the engine.
I also have a BMS OCC on the flapper side and collect nothing measurable there. If it did not require effort to do, I would simply remove the BMS unit and return that loop to stock.
I also have a BMS OCC on the flapper side and collect nothing measurable there. If it did not require effort to do, I would simply remove the BMS unit and return that loop to stock.
Just the Mishimoto occ. Other than that it's just a matter of finding where it fits best with your setup
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My OCC is bigger than the Mishimoto and I have to drain it all the time to keep it from filling. With a Mishimoto, I would have to drain once a month or more to be safe. Mine is difficult to access and I would hate to have to drain it even more often. Only critique of the Mishimoto is that it should hold more.
The Mishimoto occ's have a bottom plug for draining or for routing a drain hose to a more accessible location.
Should route a drain to the downpipe. Then we could activate diesel mode
Ghost Cam
Burble
Diesel
ive been considering this mod and even picked up 2 mishimoto occ...i was debating to do it now or after i broke in the motor
I am not 100% sure how you intend to use the catch cans, but this is what I have learned. For the vacuum side, you want an efficient catch can that will extract the most oil possible, and the Mishimoto has gained the reputation as one of the best at that. For the VTA or vent to inlet side, you want a very free flowing can, something that will not allow back pressure to build up, the BMS is supposedly the highest flowing can with almost no restriction. As you can likely guess, the higher flowing cans are usually less efficient and the most efficient are usually the lower flowing cans.
This is the set-up is what I have installed.
This is the set-up is what I have installed.
Rob@RBTurbo
Lieutenant
To Velocity26: Couldn't have said it better myself. Thanks for chiming in!
BTW, the latest batch is down to only a few more kits. Oh and I also will be making our last shipments Saturday (tomorrow) before a week long vacation- so if anyone was wanting a kit quickly now is certainly the time.
Rob
BTW, the latest batch is down to only a few more kits. Oh and I also will be making our last shipments Saturday (tomorrow) before a week long vacation- so if anyone was wanting a kit quickly now is certainly the time.
Rob
After the discussion with Rob, i think i understand the System quite well.
But what still confuses me is that the aim of providing vacuum on either the low load or high load side does not fit to the choice of OCC which is recommended.
To summarize:
High side= no real vacuum, but a high Filtration OCC would maybe hinder the flow- therefore a high flowing one gets used to provide a crankcase Ventilation with the least resistance. Besides that it is outdated my conclusion is that running VTA then is superior at least when rated from an healthy engine Point of view (because you cannot have less resistance than running VTA with nothing in between).
Low Side= vacuum on all Events besides high load. You want to have vacuum to Keep you engine clean & healthy and because it is better for Piston rings etc.
But what i dont understand here is: If the vacuum Comes from the TB you will loose vacuum if you put an high Filtration OCC like the mishmoto one in between, because it hinders vacuum flowing from TB to the VC!
It really makes no sense: If we want to have the highest vacuum possible on the low load side, using an high flowing OCC instead of an high Filtration one would be the best choice?!
Up to now i am running stock PCV System on low load- i really want to have a good System there, but the aim= providing highest vacuum & catching contamination through a OCC for me seem to be contrary to each other. So one has to choose wether he wants to have the best vacuum possible (no OCC) or the highest catching (Mishmoto OCC) and i am not sure, what´s better tbh.
Rob's kit supplies a "T" for the large vacuum port at the the throttle body, there is no need to tap anything for his kit.
I think you mostly understand how PCV works, but you may not fully understand the needs of the engine.
At low load a healthy engine has minimal blow-by and very little vacuum is needed to create negative crankcase pressure. You cannot have a large unrestricted vacuum pulling from the crankcase as this could implode seals and gaskets. This would also cause uncontrolled air entering the manifold and be a large vacuum leak.
The stock system uses the PCV valve to restrict the volume of air that can be pulled from the crank case. Regardless of how free flowing the catch can is, the PCV valve is intended to be the restricting factor. At low load, this should be plenty of flow to create a small negative pressure (vacuum) on the crank case. At the opposite end of the system you have the flapper valve. In the low load (closed) position, the flapper has a small orifice which allows air to be pulled into the crankcase and keep the PCV side from creating too much negative pressure in the crank case. (I though that my flapper was allowing too much air into the crankcase and replaced it with a check valve. This was a bad idea since it allowed my crankcase to be pulled to the same vacuum as the intake manifold and it "sucked" air through my oil filler cap causing a loud whistle.)
At high load (under boost) an engine can create a MUCH larger volume of blow-by. This amount would exceed the flow that a PCV valve would allow to be released from the crankcase. Without a free-flowing escape route, the crank-case would quickly pressurize and potentially expel the seals, gaskets and oil. In this high load state you need a high flow capacity to allow the system to vent without pressure build-up. A high efficiency catch can would not likely have enough flow to evacuate the flow without creating significantly more pressure in the crankcase. The high flow simulates a VTA system but also adds a filter to keep the oil from spewing out to atmosphere.
Thanks, very good Infos you are providing !!! Where you have them from?
When talking about the flapper valve you mean the valve inside the vent hose?
I understand that the pcv Needs to be in place for restricting the volume of vacuum which gets pulled by the intake manifold.
What i dont understand is how the flapper valve also restricts the volume? If i am right in low load the PCV has 2 "sources" from where it pulls: the vent hose with the small orifice in the flapper valve with fresh air and the crankcase with blowby. If we now Limit the volume through the vent house (via orifice) wouldnt this result in higher vacuum in the crankcase? If the PCV Limits the volume of air (vacuum) why would we Need another "limiter of volume"?
I would think that the vacuum gets pulled from the source where the least restriction is? This would mean running VTA like i do, without a flapper valve & Vent hose would be bad, cause the low load side does not pull on the crankcase (or at least not as much as in oem), it pulls on the VTA "Hose" without the flapper valve? I also think running an OCC on the high load side deletes the flapper valve and vent hose, doesnt it?
AD-E uses another System: They delete the PCV (and therefore the seperation between low load and high load) completely and run just one breather System (if OCC, VTA or OEM depends on your choice). After dealing with this Topic, altough i think Andy knows his stuff really well, i would think that this Setup is not really good? Cause there is no vacuum source on the low load side left?
I learned a lot from your post, but no matter what you think about my question i still think that an OCC in between the PCV and the vacuum source (TB) would result in less vacuum being pulled, especially with a high filtering OCC like Mishmotor one?
Again thanks for your thoughts, looking Forward for your answers!
When talking about the flapper valve you mean the valve inside the vent hose?
I understand that the pcv Needs to be in place for restricting the volume of vacuum which gets pulled by the intake manifold.
What i dont understand is how the flapper valve also restricts the volume? If i am right in low load the PCV has 2 "sources" from where it pulls: the vent hose with the small orifice in the flapper valve with fresh air and the crankcase with blowby. If we now Limit the volume through the vent house (via orifice) wouldnt this result in higher vacuum in the crankcase? If the PCV Limits the volume of air (vacuum) why would we Need another "limiter of volume"?
I would think that the vacuum gets pulled from the source where the least restriction is? This would mean running VTA like i do, without a flapper valve & Vent hose would be bad, cause the low load side does not pull on the crankcase (or at least not as much as in oem), it pulls on the VTA "Hose" without the flapper valve? I also think running an OCC on the high load side deletes the flapper valve and vent hose, doesnt it?
AD-E uses another System: They delete the PCV (and therefore the seperation between low load and high load) completely and run just one breather System (if OCC, VTA or OEM depends on your choice). After dealing with this Topic, altough i think Andy knows his stuff really well, i would think that this Setup is not really good? Cause there is no vacuum source on the low load side left?
I learned a lot from your post, but no matter what you think about my question i still think that an OCC in between the PCV and the vacuum source (TB) would result in less vacuum being pulled, especially with a high filtering OCC like Mishmotor one?
Again thanks for your thoughts, looking Forward for your answers
!There are several people that understand the N54 PCV system and have been nice enough to share with us here and on other forums. Rob, Tony, Terry and others have contributed to the wealth of knowledge that we have available to anyone willing to spend the time searching and sifting to find the gems of knowledge.
Yes, the flapper is the valve that attaches to the valve cover and has the vent tube that runs to the turbo air intake.
The idea behind two orifices (PCV and Flapper) is that the PCV has a larger orifice and the flapper has a smaller one. because of the restriction at the flapper orifice, the crankcase of a healthy engine will always see some vacuum at low load, but the orifice keeps the negative pressure from getting too high. I am sure that the engineers spent some time determining the orifice sizes to reach the optimal relationship between the two to keep the negative pressure within limits.
Everything you put into a system causes some restriction, simply adding longer tubing adds restriction to the system. What is important is that the catch can is able to flow the volume of air that the PCV valve allows without causing excessive restriction. The orifice size through the catch can is larger than that of the PCV valve (it can flow more) so it does not cause a meaningful reduction in flow to the system.
If we remove the flapper valve entirely (as you suggested) the crankcase would never be able to have ANY vacuum at all. The small amount of vacuum flow allowed by the PCV valve would be drawn in from the open ~3/4" VTA tube and no vacuum could ever be achieved in the crankcase. Some vacuum is desirable to keep more oil within the seals and gaskets. I also believe that pure VTA systems are illegal in most places that check for that sort of thing.
I felt that I could improve on what BMW had designed and I did not like that the flapper had the orifice and allowed a constant vacuum "leak" into the system and decided to replace the flapper with a check valve. This would seal the flapper side completely under low load, but would open with slight pressure and allow gasses to escape before the crankcase built any significant pressure. My engine is low mileage and healthy with almost no blow-by at idle. With the PCV valve drawing the amount allowed, and no orifice on the flapper side allowing air in, it quickly drew the crankcase to the same vacuum as in the intake manifold. The seals and gaskets were not designed to resist that much vacuum and loud "whistles" developed where air was being drawn in through the seals and the oil filler cap. This is BAD, it can damage the seals and dislodge the gaskets. Also, under high load (boost), the check valve would hold some pressure within the crankcase and be a restriction to gasses flowing out (neither a good thing). This system was removed within minutes of being installed.
I guess the difference between the two "schools of thought" is whether a PCV is necessary at all. Some people feel that you should plug the vacuum ports in the head and place two VTA tubes at the two openings and call it a day. This is illegal in most places and many states here in the USA check for this annually. I personally believe that having a PCV system helps to control the oil (keep it in the engine) and also reduces emissions (pollution and oil spraying in the engine compartment).
Yes, the flapper is the valve that attaches to the valve cover and has the vent tube that runs to the turbo air intake.
The idea behind two orifices (PCV and Flapper) is that the PCV has a larger orifice and the flapper has a smaller one. because of the restriction at the flapper orifice, the crankcase of a healthy engine will always see some vacuum at low load, but the orifice keeps the negative pressure from getting too high. I am sure that the engineers spent some time determining the orifice sizes to reach the optimal relationship between the two to keep the negative pressure within limits.
Everything you put into a system causes some restriction, simply adding longer tubing adds restriction to the system. What is important is that the catch can is able to flow the volume of air that the PCV valve allows without causing excessive restriction. The orifice size through the catch can is larger than that of the PCV valve (it can flow more) so it does not cause a meaningful reduction in flow to the system.
If we remove the flapper valve entirely (as you suggested) the crankcase would never be able to have ANY vacuum at all. The small amount of vacuum flow allowed by the PCV valve would be drawn in from the open ~3/4" VTA tube and no vacuum could ever be achieved in the crankcase. Some vacuum is desirable to keep more oil within the seals and gaskets. I also believe that pure VTA systems are illegal in most places that check for that sort of thing.
I felt that I could improve on what BMW had designed and I did not like that the flapper had the orifice and allowed a constant vacuum "leak" into the system and decided to replace the flapper with a check valve. This would seal the flapper side completely under low load, but would open with slight pressure and allow gasses to escape before the crankcase built any significant pressure. My engine is low mileage and healthy with almost no blow-by at idle. With the PCV valve drawing the amount allowed, and no orifice on the flapper side allowing air in, it quickly drew the crankcase to the same vacuum as in the intake manifold. The seals and gaskets were not designed to resist that much vacuum and loud "whistles" developed where air was being drawn in through the seals and the oil filler cap. This is BAD, it can damage the seals and dislodge the gaskets. Also, under high load (boost), the check valve would hold some pressure within the crankcase and be a restriction to gasses flowing out (neither a good thing). This system was removed within minutes of being installed.
I guess the difference between the two "schools of thought" is whether a PCV is necessary at all. Some people feel that you should plug the vacuum ports in the head and place two VTA tubes at the two openings and call it a day. This is illegal in most places and many states here in the USA check for this annually. I personally believe that having a PCV system helps to control the oil (keep it in the engine) and also reduces emissions (pollution and oil spraying in the engine compartment).
