I am really curious about the implementation of the vacuum pump ... do you use a PCV valve to restrict the flow, or is there another way to restrict the flow, or amount of vacuum that it can put on the crankcase?
PCV talk
- Thread starter lamia2super
- Start date
I have an RB pcv with the rb pcv delete setup and i retain the oem flapper as well. I have two mishimoto occ's but one is a 3 port which is less restrictive. Ports are plugged in head
It is an electric vacuum pump, it creates a constant vacuum source regardless if the engine is on boost or not. This resolves the need to have two PCV systems.
Need some opinions as i'm still figuring out this pcv setup....
My plan was to mimic this setup, but do it my way.
http://www.n54tech.com/forums/showthread.php?t=37423
I wanted to keep the hose to intake filter as short as possilbe. This routing still allows the engine cover to be almost in oem location (slightly off angle left to right). Trimmed some foam & will lose 1 front cap screw NBD. The flapper is removed (felt like it literally did nothing) & 3/4 hose routed down to the bottom mount filter. I was able to thread a barbed fitting into the factory pcv cap & block the internal passage (kind of a combo of Andy's delete fitting & Rob's pcv). This is going to get a 3/8 hose routed down & Tee'd in as shown in the n54tech thread. Head is not tapped & would prefer not to until I NEED to pull the cover; as of now there is no other reason. I realize this isn't the optimum setup but really am looking to do something to get me up & running & tuning. At that point I would reevaluate.
But then just when I thought I had a plan, I had another idea...
Would it be "better" if all the hoses route to the same place, but the OCC was on the 3/4 hose going directly to the bottom mount (and still routing pcv to 3/8 vacuum Tee on throttle body)? I wouldn't have to drill/retap the OCC, just come up w/ a simple mount off the threaded insert behind it.
Am I doing anything COMPLETELY wrong either way?
My plan was to mimic this setup, but do it my way.
http://www.n54tech.com/forums/showthread.php?t=37423
I wanted to keep the hose to intake filter as short as possilbe. This routing still allows the engine cover to be almost in oem location (slightly off angle left to right). Trimmed some foam & will lose 1 front cap screw NBD. The flapper is removed (felt like it literally did nothing) & 3/4 hose routed down to the bottom mount filter. I was able to thread a barbed fitting into the factory pcv cap & block the internal passage (kind of a combo of Andy's delete fitting & Rob's pcv). This is going to get a 3/8 hose routed down & Tee'd in as shown in the n54tech thread. Head is not tapped & would prefer not to until I NEED to pull the cover; as of now there is no other reason. I realize this isn't the optimum setup but really am looking to do something to get me up & running & tuning. At that point I would reevaluate.
But then just when I thought I had a plan, I had another idea...
Would it be "better" if all the hoses route to the same place, but the OCC was on the 3/4 hose going directly to the bottom mount (and still routing pcv to 3/8 vacuum Tee on throttle body)? I wouldn't have to drill/retap the OCC, just come up w/ a simple mount off the threaded insert behind it.
Am I doing anything COMPLETELY wrong either way?
You may not understand what the flapper does, and think that it is doing nothing.
When you are not under boost, the flapper is in the closed position and allows the PCV system to draw some vacuum
on the crankcase. When the intake is under boost, the check-valve closes and that side of the PCV system stops working. With no vacuum getting into the crankcase, any blow-by would build pressure. This is when the flapper is pushed open and the pressure can escape freely and keep any pressure from building. If you remove the flapper completely, the no-boost pcv will simply pull air through from the flapper side, with no resistance (cannot build vacuum in crankcase). If you remove the flapper, you might as well eliminate the entire low side and go complete VTA (vent to atmosphere) since you would never build any vacuum in the crankcase anyway. Doing that would eliminate a useless vacuum leak.
When you are not under boost, the flapper is in the closed position and allows the PCV system to draw some vacuum
on the crankcase. When the intake is under boost, the check-valve closes and that side of the PCV system stops working. With no vacuum getting into the crankcase, any blow-by would build pressure. This is when the flapper is pushed open and the pressure can escape freely and keep any pressure from building. If you remove the flapper completely, the no-boost pcv will simply pull air through from the flapper side, with no resistance (cannot build vacuum in crankcase). If you remove the flapper, you might as well eliminate the entire low side and go complete VTA (vent to atmosphere) since you would never build any vacuum in the crankcase anyway. Doing that would eliminate a useless vacuum leak.
You are not actually drawing any meaningful vacuum from the air filter assembly, unless you have a significant restriction on the air flow (which I would doubt). The main reason people choose to route the VTA to the filter assembly is to keep it from spewing oil and smell elsewhere in the engine compartment. Any bad smell would be pulled into the turbo and combusted.
For the manifold side to create any meaningful vacuum in the crankcase, you need to have a way to temporarily block the other side. That is exactly the function of the flapper. It allows the "primary" PCV to operate efficiently when the manifold is under vacuum, then switches position, created a free flowing path for when the manifold is under boost and the primary PCV is not operating. Your system would be perfect if you simply put the flapper back in the loop.
I also thought that the flapper was unnecessary and removed it. I attempted to replace it with check valves and learned that the flapper performs several functions (and performs them very well) and it would take a lot of effort and equipment to replicate what it does. It provides a metered restriction to allow the primary PCV to draw vacuum on the crankcase, while keeping that vacuum at a manageable level (not too much). Then it opens, with almost no effort, and allows a large volume of flow to freely pass to keep any pressure from building within the crankcase. The more you know about the flapper, the more you realize that there was significant thought put into designing that part.
For the manifold side to create any meaningful vacuum in the crankcase, you need to have a way to temporarily block the other side. That is exactly the function of the flapper. It allows the "primary" PCV to operate efficiently when the manifold is under vacuum, then switches position, created a free flowing path for when the manifold is under boost and the primary PCV is not operating. Your system would be perfect if you simply put the flapper back in the loop.
I also thought that the flapper was unnecessary and removed it. I attempted to replace it with check valves and learned that the flapper performs several functions (and performs them very well) and it would take a lot of effort and equipment to replicate what it does. It provides a metered restriction to allow the primary PCV to draw vacuum on the crankcase, while keeping that vacuum at a manageable level (not too much). Then it opens, with almost no effort, and allows a large volume of flow to freely pass to keep any pressure from building within the crankcase. The more you know about the flapper, the more you realize that there was significant thought put into designing that part.
I can plumb the flapper back in fairly easily if it's that important. I was basing this concpet off a basic visual inspection & the fact if I try to blow through it, it doesn't block flow completely in 1 direction & takes barely any pressure in the other. And weeding through countless PCV opinons online. That raises these questions now:
1. Does it matter where the flatter is located? Oriented? Does it have to be directly off valve cover or can i splice it in farther down the hose & use it like a 45*ish coupler (yes I would confirm flow path is same as oem intended)?
2. Would I be better off putting the OCC on the 3/4 side? Or the 3/8 side (completely mimicking the N54tech thread)?
3. Did you ever make a thread w/ your PCV/check valve experimenting?
I do not think that it matters where the flapper is located, but it utilizes gravity to close so you need to keep the orientation similar to what how it sits on the valve cover.
I have an OCC on both sides of the system, a BMS can on the 3/4 side, and low flow can on the vacuum side. I collect a significant amount of oil on the vacuum (3/8 side) and almost nothing on the 3/4 side. If you have more blow-by that me, or drive your car significantly rougher than I do, your results may vary. If you see significant oil getting to your air filter, you might consider adding a catch can to the 3/4 line. Make sure that you use a high flow can like the BMS one.
I never made a thread, but the information is posted on several threads where others were fighting problems with their systems. Basically, I removed the flapper and installed a large check valve to replace it. Within a few seconds of starting the engine, the manifold was drawing so much vacuum from the crankcase that the the oil cap and other gaskets started to whistle (a bad thing). The orifice in the flapper allows the crankcase to develop some vacuum, but allows enough flow past to keep the vacuum from getting too high and stressing the gaskets and seals. Under boost, a check valve will require a few psi to defeat the spring pressure and open. That means that the crankcase is constantly exposed to the pressure required to open the check valve. The factory flapper has a large surface area and no spring, since it uses gravity to close it, so it requires almost no effort to open. The final option, your method of removing the flapper and leaving the passage open, allowed the 3/8 side to draw air from the 3/4 side with no restriction. That was basically a constant vacuum leak that could not ever create any vacuum in the crankcase. It was basically no better than having both sides open to the atmosphere from a PCV perspective.
I have an OCC on both sides of the system, a BMS can on the 3/4 side, and low flow can on the vacuum side. I collect a significant amount of oil on the vacuum (3/8 side) and almost nothing on the 3/4 side. If you have more blow-by that me, or drive your car significantly rougher than I do, your results may vary. If you see significant oil getting to your air filter, you might consider adding a catch can to the 3/4 line. Make sure that you use a high flow can like the BMS one.
I never made a thread, but the information is posted on several threads where others were fighting problems with their systems. Basically, I removed the flapper and installed a large check valve to replace it. Within a few seconds of starting the engine, the manifold was drawing so much vacuum from the crankcase that the the oil cap and other gaskets started to whistle (a bad thing). The orifice in the flapper allows the crankcase to develop some vacuum, but allows enough flow past to keep the vacuum from getting too high and stressing the gaskets and seals. Under boost, a check valve will require a few psi to defeat the spring pressure and open. That means that the crankcase is constantly exposed to the pressure required to open the check valve. The factory flapper has a large surface area and no spring, since it uses gravity to close it, so it requires almost no effort to open. The final option, your method of removing the flapper and leaving the passage open, allowed the 3/8 side to draw air from the 3/4 side with no restriction. That was basically a constant vacuum leak that could not ever create any vacuum in the crankcase. It was basically no better than having both sides open to the atmosphere from a PCV perspective.
I think that VTA stinks, literally, and it can also make a mess. They are also illegal in places where they check that sort of thing.
That would be your best bet, just make your that your can(s) have enough flow capacity that they will not restrict the gasses exiting the motor. Under full boost, there is the potential for a lot of gasses trying to get out.
I'm in the process of routing my flapper somewhere as well. Has anyone else pursued the vacuum pump idea? Does it need to be controlled?
