RB External PCV Help

megaman416

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Hi all,

On the RB External PCV kit I understand how it works on the low side. On the high side I plan on using a bms can. Where are you routing the out to on a plugged head setup?

Thanks
 

Jeffman

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Outlet from the BMS OCC can go back to the rear stock inlet or vent to atmosphere. Mine goes to the stock rear inlet.
 

megaman416

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Thanks. Should have mentioned single turbo. Preference is not to air due to smell and it being a street car.
 

doublespaces

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Personally i route the high side to a mishimoto style catch can with the internal stone filter removed so it isntisa restriction. I may outpsome steel wool or something in there to help catch a little more vapor.

Then I have a 3/4" barb going out where i hook up some gates hose and stuff the flapper in there and vta.

I will eventually do one of two things:

Route to my intake pipe
Route to my exhaust pipe

Routing to exhaust is a bit more tricky since you have to worry about check valves to prevent backfires and also allowing the cover to breathe during engine vacuum.

So I'll probably just route it to my intake pipe.
 

steve335i

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For the high side outlet on a single turbo , you could either vent to atmosphere which a lot of people do and claim no issues , or you could route the hose to the air filter on the turbo so it would pull a little bit of vacuum like it is designed to in stock form. Which will help a few different things. RB told me that would be best way to do high side on ST car.
 

doublespaces

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For the high side outlet on a single turbo , you could either vent to atmosphere which a lot of people do and claim no issues , or you could route the hose to the air filter on the turbo so it would pull a little bit of vacuum like it is designed to in stock form. Which will help a few different things. RB told me that would be best way to do high side on ST car.

No real noteworthy vacuum is being pulled there. It just sucks the fumes away and is the best option in my opinion.
 

megaman416

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Personally i route the high side to a mishimoto style catch can with the internal stone filter removed so it isntisa restriction. I may outpsome steel wool or something in there to help catch a little more vapor.

Then I have a 3/4" barb going out where i hook up some gates hose and stuff the flapper in there and vta.

I will eventually do one of two things:

Route to my intake pipe
Route to my exhaust pipe

Routing to exhaust is a bit more tricky since you have to worry about check valves to prevent backfires and also allowing the cover to breathe during engine vacuum.

So I'll probably just route it to my intake pipe.

Exhaust on the dp was what I was thinking. 10an from flapper delete to bms can, exit 10an to dp where a vibrant check valve and scavenger sit.

Thoughts?

Also if routing to intake are you keeping factory flapper? Using catch can?
 
Last edited:

MattGu40

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This setup got rid of 90% of the smoke i had while decelerating/idle

I am running the normal BMS catch can and RB external.
From RB PCV 6AN modified chinesium catch can very well made for the price with steel whool traped inside the filter cage. then -6 to the intake manifold. Plugged head ports.

Is 6AN too small? i guess not bigger ID than the RB external valve.

My question is how does the RB external valve works ? Simply as a low cracking pressure checkvalve ?
25 psi going straight at it while on boost wont hurt it ? no need for additional catch can ?
 

doublespaces

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Exhaust on the dp was what I was thinking. 10an from flapper delete to bms can, exit 10an to dp where a vibrant check valve and scavenger sit.

Thoughts?

Please try it and report back. Try to take some vacuum measurements at idle and under boost. Just be aware, that when you have a check valve, that does protect from a backfire but at the same time, that completely halts airflow toward your crank case. This means at idle, you may have the 'howling seals' issue because you've completely restricted this air flow. The flapper is a swing valve has a hole in the center of the 'flap' so it behaves as an orifice restriction when closed, it doesn't seal completely like your check valve will.
upload_2018-8-20_1-48-11.png


So what you'd need, technically, is another check valve that has a cracking pressure of a few psi, something that engine vacuum can overcome. Then put a filter on the other side since air will be drawn in.

megaman416 said:
Also if routing to intake are you keeping factory flapper? Using catch can?

I'm not sure if I'll keep the factory flapper or not. I may just pull the flapper, put the stone filter back in my high side catch can and let that stone filter do the 'restricting'. This does add a blockage when it comes to on-boost situations and increases my potential to have positive crank case pressure, but if that occurs I'll address that when I notice a problem with turbo oil drainage, smoking, etc. But I'm not putting out any crazy power numbers so my suspicion is that it will be okay. But currently the flapper is still there, just relocated behind my high side catch can.

My setup is explained in detail here:

https://bmw.spoolstreet.com/threads/2009-e93-ad-e-single-turbo-build.959/page-13#post-52417


This setup got rid of 90% of the smoke i had while decelerating/idle

I am running the normal BMS catch can and RB external.
From RB PCV 6AN modified chinesium catch can very well made for the price with steel whool traped inside the filter cage. then -6 to the intake manifold. Plugged head ports.

Is 6AN too small? i guess not bigger ID than the RB external valve.

6AN isn't too small, because the PCV side, aka low side only operates in one direction, and it operates under vacuum only, its not a Vent To Atmosphere line which needs to be free of pressure obstructions.

MattGu40 said:
My question is how does the RB external valve works ? Simply as a low cracking pressure checkvalve ?
25 psi going straight at it while on boost wont hurt it ? no need for additional catch can ?

From what I can tell, the RB external valve is simply a non-spring loaded check valve. The cracking pressure is pretty much nil, you can easily switch it back and forth using your mouth with ease.

Personally, I run a Russel check valve between my intake manifold and my low side catch can so my catch can isn't getting pressurized. You can imagine what Kind of mess would occur if a line came loose or something broke. This means I could actually just eliminate the RB PCV valve and just keep this secondary check valve since they are accomplishing the same thing. But Russell isn't exactly Toyota, and if it failed the last thing I would want is a bunch of boost spraying oil from my catch can back into my motor. Not to mention, the Russell valve has a higher cracking pressure, I'm actually looking for a 6AN valve that is not.

The problem with ball check valves, is that they can slam closed when pressure hits from one direction, such as from boost onset and this can crack them. But last I heard, RB is using a Toyoto part, and OEM parts are pretty dang reliable generally speaking.

The RB valve allows the engine vacuum when at idle or deceleration to suck on the crank case, into the intake manifold. But when you step on the gas, the boost that enters the manifold tries to go back up that same line, but the RB valve is there and closes, preventing your boost pressure from entering the crank case. Meanwhile, blowby from the cylinders is exiting the flapper valve into the rear inlet, intake cone/pipe, VTA, through 10AN flapper delete or whatever you happen to have there. This is a larger line beacuse there is no vacuum source on the other side to suck it out(besides the previously mentioned intake pipe/cone options which have very limited vacuum). You hope this is happening without building up positive pressure as this causes the oil drains on the turbos to get backed up, causing smoking problems and other issues. This is why they use the BMS catch can, because it has virtually no filtration element and poses little restriction to the blowby fumes trying to escape the motor.
 

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If you want to retain OEM-like PCV functionality (which is wise IMO), you do not want to attempt to use the exhaust for any connection points. Generally speaking when you all are trying to do anything different, you are affecting numerous other things that have to be considered as an impact of the overall system functionality change.

In low load function, the pcv valve is pulling just a tiny bit of vacuum (not much is needed), when doing this the clean filtrated air from the high side connection is being pulled back through the crankcase via pcv valve all the way into the vacuum reference position in the intake. If you had been using the exhaust, then you'd using exhaust as your "filtrated fresh air source" to replenish the crankcase atmosphere at low loads instead. Obviously you do not want to do this, at least not without a lot more thinking and a complete revision of any retained OE system functionality.

In short your best bet is to find a way to connect the high load side back between the air filter and turbo (even if ST). This does provide a bit of assist to help ventilate the crankcase in high loads, keeping in mind that any assist is a good thing and it always provides filtrated fresh air as a source into the crankcase during low load "vacuuming". It also of course keeps the roads cleaner and the smells down. Alternatively some let the high side connection VTA which is not something we'd recommend, but it would be wiser than plumbing it into the exhaust.

Rob
 
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[email protected]

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From what I can tell, the RB external valve is simply a non-spring loaded check valve. The cracking pressure is pretty much nil, you can easily switch it back and forth using your mouth with ease.

Personally, I run a Russel check valve between my intake manifold and my low side catch can so my catch can isn't getting pressurized. You can imagine what Kind of mess would occur if a line came loose or something broke. This means I could actually just eliminate the RB PCV valve and just keep this secondary check valve since they are accomplishing the same thing. But Russell isn't exactly Toyota, and if it failed the last thing I would want is a bunch of boost spraying oil from my catch can back into my motor. Not to mention, the Russell valve has a higher cracking pressure, I'm actually looking for a 6AN valve that is not.

The problem with ball check valves, is that they can slam closed when pressure hits from one direction, such as from boost onset and this can crack them. But last I heard, RB is using a Toyoto part, and OEM parts are pretty dang reliable generally speaking.

The RB valve allows the engine vacuum when at idle or deceleration to suck on the crank case, into the intake manifold. But when you step on the gas, the boost that enters the manifold tries to go back up that same line, but the RB valve is there and closes, preventing your boost pressure from entering the crank case. Meanwhile, blowby from the cylinders is exiting the flapper valve into the rear inlet, intake cone/pipe, VTA, through 10AN flapper delete or whatever you happen to have there. This is a larger line beacuse there is no vacuum source on the other side to suck it out(besides the previously mentioned intake pipe/cone options which have very limited vacuum). You hope this is happening without building up positive pressure as this causes the oil drains on the turbos to get backed up, causing smoking problems and other issues. This is why they use the BMS catch can, because it has virtually no filtration element and poses little restriction to the blowby fumes trying to escape the motor.

The PCV valve is in fact a high quality OE Toyota valve which we have adapted into the N54 environment. Indeed reliability is key and these valves are meant to be able to sustain great function over much time- as such despite being a maintenance item they still have great lifespan potential. However it is not "just a simple open/closed check valve". PCV valves are calibrated devices that open or close at varying levels via a plunger and adjust airflow accordingly, pending on what kind of airflow is needed through a crankcase in particular conditions (see attachment and understand during backfire and/or boosted conditions it operates the same).

As such under very high vacuum (ie. decel, idle) they limit flow. Reason being is that you do not want full vacuum applied to your crankcase under any conditions, as such limiting the vacuum is what is desirable and this is integrated into the valve itself.

Under lower vacuum (ie. light decel, moderate cruise, most throttle part open non-boosted conditions) they can flow the most, not that it is a lot but that is not necessary only enough to keep the crankcase clean is what we are looking for here.

At 0 vac upward they close entirely (sealed tight) and do nothing, and this is where the vacuum assist from the high side connection comes into play.

All said if you are getting lots of blowby there comes a point where there is going to be no miracle fix for you- your engine may just be degraded and need overhaul. This assuming of course you have no other weak links floating around that you have not addressed.

Rob
pcv_system_valve_operation.jpg
 
Last edited:

doublespaces

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Wouldnt it hurt the air flow? Because than im also adding some steel wool to keep the intake a little bit cleaner.
I mean, anything in there is a restriction. The question is, will the restriction make a difference that actually matters to you. This isn't something I could say for sure because there are a lot of variables to that. I think a bit of steel wool or something similar would be fine, but the best way is to just run it to the intake.
 

megaman416

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Jan 25, 2018
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If you want to retain OEM-like PCV functionality (which is wise IMO), you do not want to attempt to use the exhaust for any connection points. Generally speaking when you all are trying to do anything different, you are affecting numerous other things that have to be considered as an impact of the overall system functionality change.

In low load function, the pcv valve is pulling just a tiny bit of vacuum (not much is needed), when doing this the clean filtrated air from the high side connection is being pulled back through the crankcase via pcv valve all the way into the vacuum reference position in the intake. If you had been using the exhaust, then you'd using exhaust as your "filtrated fresh air source" to replenish the crankcase atmosphere at low loads instead. Obviously you do not want to do this, at least not without a lot more thinking and a complete revision of any retained OE system functionality.

In short your best bet is to find a way to connect the high load side back between the air filter and turbo (even if ST). This does provide a bit of assist to help ventilate the crankcase in high loads, keeping in mind that any assist is a good thing and it always provides filtrated fresh air as a source into the crankcase during low load "vacuuming". It also of course keeps the roads cleaner and the smells down. Alternatively some let the high side connection VTA which is not something we'd recommend, but it would be wiser than plumbing it into the exhaust.

Rob

Rob what are your thoughts on retaining the flapper on the high side when routing through a bms can to the filter? Is its function needed or would it be a restriction on high boost singles?
 

megaman416

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Jan 25, 2018
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Please try it and report back. Try to take some vacuum measurements at idle and under boost. Just be aware, that when you have a check valve, that does protect from a backfire but at the same time, that completely halts airflow toward your crank case. This means at idle, you may have the 'howling seals' issue because you've completely restricted this air flow. The flapper is a swing valve has a hole in the center of the 'flap' so it behaves as an orifice restriction when closed, it doesn't seal completely like your check valve will.
View attachment 15013

So what you'd need, technically, is another check valve that has a cracking pressure of a few psi, something that engine vacuum can overcome. Then put a filter on the other side since air will be drawn in.



I'm not sure if I'll keep the factory flapper or not. I may just pull the flapper, put the stone filter back in my high side catch can and let that stone filter do the 'restricting'. This does add a blockage when it comes to on-boost situations and increases my potential to have positive crank case pressure, but if that occurs I'll address that when I notice a problem with turbo oil drainage, smoking, etc. But I'm not putting out any crazy power numbers so my suspicion is that it will be okay. But currently the flapper is still there, just relocated behind my high side catch can.

My setup is explained in detail here:

https://bmw.spoolstreet.com/threads/2009-e93-ad-e-single-turbo-build.959/page-13#post-52417




6AN isn't too small, because the PCV side, aka low side only operates in one direction, and it operates under vacuum only, its not a Vent To Atmosphere line which needs to be free of pressure obstructions.



From what I can tell, the RB external valve is simply a non-spring loaded check valve. The cracking pressure is pretty much nil, you can easily switch it back and forth using your mouth with ease.

Personally, I run a Russel check valve between my intake manifold and my low side catch can so my catch can isn't getting pressurized. You can imagine what Kind of mess would occur if a line came loose or something broke. This means I could actually just eliminate the RB PCV valve and just keep this secondary check valve since they are accomplishing the same thing. But Russell isn't exactly Toyota, and if it failed the last thing I would want is a bunch of boost spraying oil from my catch can back into my motor. Not to mention, the Russell valve has a higher cracking pressure, I'm actually looking for a 6AN valve that is not.

The problem with ball check valves, is that they can slam closed when pressure hits from one direction, such as from boost onset and this can crack them. But last I heard, RB is using a Toyoto part, and OEM parts are pretty dang reliable generally speaking.

The RB valve allows the engine vacuum when at idle or deceleration to suck on the crank case, into the intake manifold. But when you step on the gas, the boost that enters the manifold tries to go back up that same line, but the RB valve is there and closes, preventing your boost pressure from entering the crank case. Meanwhile, blowby from the cylinders is exiting the flapper valve into the rear inlet, intake cone/pipe, VTA, through 10AN flapper delete or whatever you happen to have there. This is a larger line beacuse there is no vacuum source on the other side to suck it out(besides the previously mentioned intake pipe/cone options which have very limited vacuum). You hope this is happening without building up positive pressure as this causes the oil drains on the turbos to get backed up, causing smoking problems and other issues. This is why they use the BMS catch can, because it has virtually no filtration element and poses little restriction to the blowby fumes trying to escape the motor.

How much boost and what turbo you running? Trying determine where the flapper would become a restriction if it would vs just being open through a bms can to the filter. Not sure if its function is needed on the high side.
 

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Rob what are your thoughts on retaining the flapper on the high side when routing through a bms can to the filter? Is its function needed or would it be a restriction on high boost singles?

The flapper assembly is a fundamental requirement for the PCV system to operate correctly primarily when operating under low load conditions where the flapper gate will swing shut, but leave a calibrated orifice to bias appropriate airflow through the crankcase which works in unison with the PCV valve. Under high load conditions the flapper gate will swing fully opens, doing nothing other than providing an opening for ventilation to occur. In short leave the flapper in place and functional if you are running a PCV setup.

Rob
 
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Rob09msport

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If you want to retain OEM-like PCV functionality (which is wise IMO), you do not want to attempt to use the exhaust for any connection points. Generally speaking when you all are trying to do anything different, you are affecting numerous other things that have to be considered as an impact of the overall system functionality change.

In low load function, the pcv valve is pulling just a tiny bit of vacuum (not much is needed), when doing this the clean filtrated air from the high side connection is being pulled back through the crankcase via pcv valve all the way into the vacuum reference position in the intake. If you had been using the exhaust, then you'd using exhaust as your "filtrated fresh air source" to replenish the crankcase atmosphere at low loads instead. Obviously you do not want to do this, at least not without a lot more thinking and a complete revision of any retained OE system functionality.

In short your best bet is to find a way to connect the high load side back between the air filter and turbo (even if ST). This does provide a bit of assist to help ventilate the crankcase in high loads, keeping in mind that any assist is a good thing and it always provides filtrated fresh air as a source into the crankcase during low load "vacuuming". It also of course keeps the roads cleaner and the smells down. Alternatively some let the high side connection VTA which is not something we'd recommend, but it would be wiser than plumbing it into the exhaust.

Rob
You know alot more then me im just checking to make sure but wouldnt the check valve double spaces planned on using prevent exhaust from entering crank case?
 

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You know alot more then me im just checking to make sure but wouldnt the check valve double spaces planned on using prevent exhaust from entering crank case?

If there were a check valve preventing any airflow (whether exhaust or clean air filtrated) from entering the crankcase (from the high load connection point) under low load conditions then you'd get no air replenishment in the crankcase, and begin pulling a lot of vacuum on the crankcase in these scenarios as there will be no relief (this is not a good thing). So basically a double whammy bad idea.

Not sure why there is continual over thoughts on these things, they are already thought out and work fairly effectively on a wide array of power ranges. The OE system works well as it is, but it can use a couple enhancements as long as functionality is fully retained (ie. "delete" parts kill this concept dead instantly). Ultimately we do not believe there is really any reason to attempt to complicate them, but it seems to be the everlasting trend on this platform for some reason.

What also seems to be a trend is the circling back to the OE-like simplicity of a functional PCV setup, after trying numerous other poorly thought out solutions. Keep it simple...

Rob
 
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Rob09msport

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If there were a check valve preventing any airflow (whether exhaust or clean air filtrated) from entering the crankcase (from the high load connection point) under low load conditions then you'd get no air replenishment in the crankcase, and begin pulling a lot of vacuum on the crankcase in these scenarios as there will be no relief (this is not a good thing). So basically a double whammy bad idea.

Not sure why there is continual over thoughts on these things, they are already thought out and work fairly effectively on a wide array of power ranges. The OE system works well as it is, but it can use a couple enhancements as long as functionality is fully retained (ie. "delete" parts kill this concept dead instantly). Ultimately we do not believe there is really any reason to attempt to complicate them, but it seems to be the everlasting trend on this platform for some reason.

What also seems to be a trend is the circling back to the OE-like simplicity of a functional PCV setup, after trying numerous other poorly thought out solutions. Keep it simple...

Rob
I def agree with your kit being the best for any twin setup I just was reading post and saw that you said pull exhaust through and wasnt sure if you missed the check valve .Wasnt saying anything was better or worse. I dont give any input when comes to pcv on these cars cause it's one of the many n54 things that confuse me to no end ,so I stick with set up from people with more knowledge than me aka you
 
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