PCV valve?

06 T-RED S/C GT

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For anyone interested, there’s a good read on the subject here;
https://www.superchargerforums.com/...ilation-how-to-breathe-when-youre-blown.2472/
Just finished reading the article and found it very interesting how the author does recommend adding catch cans and one-way check valves in conjunction with the engine's PCV valve for FI applications.

However, I'm not quite sure if this applies to just centrifugal type blowers or also with PD blowers as well :shrug:

In a forced induction system, the manifold is only providing vacuum (negative pressure) at idle, low speeds, and during deceleration. At higher engine speeds and periods of boost, the system is actually under pressure. If not controlled, the increased manifold pressure will flow backwards through the valve cover into the engine, creating positive crankcase pressure. Most PVC valves are designed so that the sudden high pressure of an engine backfire closes the valve, but even the best valves become contaminated with oil and dirt so that they no longer completely block off the manifold pressure. This problem can be addressed with the use of a one-way check valve. The check valve would work with the PCV valve to limit air flow back into the crankcase. However, the gasses must still be evacuated, and this requires the use of a second evacuation channel.

Crankcase Ventilation System, Modified for Fixed Displacement Supercharger

This schematic illustrates the basic setup

boosted-pcv-operation.png


low-speed-pcv-operation.png

basic-setup-chart.png
The second evacuation channel is actually provided by the first part of the primary intake channel. This is only possible because that part of the system is bidirectional, allowing air to flow in both directions. When the intake manifold vacuum is high but supercharger intake vacuum is relatively low, air is pulled through the crankcase in the direction of the manifold. But when the manifold is pressurized under boost, the check valve completely closes off this part of the system. When that happens, positive crankcase pressure pushes the blow-by gasses in the opposite direction. Almost simultaneously, the air flow at the supercharger intake increases greatly. The increase in airflow results in higher vacuum at the supercharger intake, which draws in the crankcase gasses.

Air/Oil Separators (Catch Cans)

Catch cans are considered a requirement with any forced induction engine, including those with supercharger systems. Whenever the crankcase ventilation system is used to circulate crankcase gasses through the intake, the need to filter the air becomes even more urgent. Dirty oil vapor can coat the entire intake system, including the valves, with an insulating layer of contaminants that may also contain corrosive elements. This layer may interfere with proper cooling and heat dissipation as well as gumming up the works.

Most importantly, oil vapor in the intake stream lowers the octane of the fuel/air mixture. This could cause engine-damaging detonation and all of the problems associated with it. Therefore, the intake of crankcase gas should always be filtered through an air/oil separator. It is important to use cans that contain oil baffles and/or some sort of filtering element. Those that require periodic draining are recommended, as the oil contained therein is contaminated and not well suited for re-use.
 
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eighty6gt

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check valves are only necessary in systems where you go from vacuum to boost in the pcv system/intake, ie: a turbo/etc. All of the roots-like systems don't need any of that nonsense.

There's that thing about lowering the octane! Look at how authoritative that writing is.

I once had a separator that allowed for oil to be returned to the crankcase, was meant for diesel engines. Because I was pulling 20+ inches of vacuum at times and almost that at idle, it just leaked and leaked. Made noise. Had to sell it.
 
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06 T-RED S/C GT

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check valves are only necessary in systems where you go from vacuum to boost in the pcv system/intake, ie: a turbo/etc. All of the roots-like systems don't need any of that nonsense.

There's that thing about lowering the octane! Look at how authoritative that writing is.

I once had a separator that allowed for oil to be returned to the crankcase, was meant for diesel engines. Because I was pulling 20+ inches of vacuum at times and almost that at idle, it just leaked and leaked. Made noise. Had to sell it.

IIRC, the Saleen VI blower has what's called a boost bypass valve which when at idle and part throttle, the engine has vacuum and pulls the bypass OPEN. Bypass OPEN equals no pressure between inlet/outlet of the SC and 0 boost. When you get on the accelerator, vacuum drops and the bypass valve shuts on it's own under spring pressure. Once closed there is no path between the outlet and inlet of the SC and you have a sealed (somewhat) outlet that builds boost.

Anyhow, would I be correct by assuming the boost bypass valve is designed to prevent the crankcase from pressurizing once vacuum drops and the bypass valve closes when going beyond part throttle/boost?
 

eighty6gt

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on the saleen blower (positive displacement) there's nothing in common with the pressure side of the system and the pcv system.

Every pd blower I know of has a bypass or you'd have a lot more losses. So no the boost bypass valve isn't what that is for.
 

06 T-RED S/C GT

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In that case, would you recommend removing the inline one way check valve or leave it in place in the event the PCV valve inside the driver's side cam cover should end up failing?
 

Midlife Crises

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In that case, would you recommend removing the inline one way check valve or leave it in place in the event the PCV valve inside the driver's side cam cover should end up failing?
The check valve you added does the same thing as the one Ford put in the cam cover. You don’t need two of them.
Just a thought; the second check valve may offer some restriction to the airflow in that tube by acting as an orifice. Reducing the amount of airflow and the amount of oil that migrates in the airstream.
 

06 T-RED S/C GT

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The check valve you added does the same thing as the one Ford put in the cam cover. You don’t need two of them.
Just a thought; the second check valve may offer some restriction to the airflow in that tube by acting as an orifice. Reducing the amount of airflow and the amount of oil that migrates in the airstream.
If the inline check valve may in fact offer some restriction to the airflow by acting as an orifice? then perhaps it could very well serve a meaningful purpose by reducing the amount of airflow and amount of oil that migrates in the airstream? At this point, I'll settle for all the help I can possible get, providing the second check valve doesn't create a potential risk for causing any type of damage to the engine :shrug:
As mentioned earlier in the thread, the catch can does indeed collect oil and gets emptied at every oil change. Therefore, it continues to function as intended, despite the addition of the second check valve inline.
 
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dlanes

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If anyone is interested in how my pcv setup looks this is pretty much the final setup.

20210429_121819.jpg
 

06 T-RED S/C GT

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Nice setup with adding the AN fittings to the valve covers including the addition of the inline check valve. Congrats :waytogo:
 

dlanes

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UPDATE:
So I figured I should update you guys on how this PCV setup has been working out. It's been a little over 2 weeks and one problem I noticed is sometimes on start up or on long drives I will have some excess blow by that will cause a little smoke in the exhaust. I assume this is from the higher vacuum which is why the stock PCV restricts airflow under vacuum. I removed the valve from the OEM PCV valve and opened the UPR check valve and inserted the OEM valve inside (I used UPR's spring since the stock spring was a little too big). The OEM valve fits and works perfect as a check valve and restriction in the opposite direction (the hole diameter is basically the same which is why it works and UPR check valve is designed to be disassembled). This should eliminate the excess blow by under high vacuum conditions.

pcvvalve.jpg
 

Riptide

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I have a TVS setup on my car and breathers installed along with a oil cap breather. On the passenger side the check valve is still installed.

After reading through this thread I still don't understand. I've asked vendors like JPC about this in the past and they said no need to remove the one way check valve but then I read on forums opinions saying otherwise.

At this point more confused than ever. lol
 

GlassTop09

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UPDATE:
So I figured I should update you guys on how this PCV setup has been working out. It's been a little over 2 weeks and one problem I noticed is sometimes on start up or on long drives I will have some excess blow by that will cause a little smoke in the exhaust. I assume this is from the higher vacuum which is why the stock PCV restricts airflow under vacuum. I removed the valve from the OEM PCV valve and opened the UPR check valve and inserted the OEM valve inside (I used UPR's spring since the stock spring was a little too big). The OEM valve fits and works perfect as a check valve and restriction in the opposite direction (the hole diameter is basically the same which is why it works and UPR check valve is designed to be disassembled). This should eliminate the excess blow by under high vacuum conditions.

View attachment 77902
Hi dlanes,

Is the UPR check valve you used the 5\8" barbed, 125 psi rated metal check valve? If so I am currently using 1 of those in the return line downstream of my catch can w\ a M6 flat washer installed under the UPR spring as an orifice (1/8" ID) to do the very same thing as you, but what you've essentially done is create an external PCV valve by doing what you've done.......I have the OEM valve covers off my 4.6L & was gonna send them to scrap (have FR Black Etched valve covers installed) until I saw this post.

Brilliant work! Am gonna follow your example for my setup.

:beer:
 

Midlife Crises

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After a couple different configurations of spending money on traps and separators and still having oil in my intercooler I gave up on the PCV system. Removed the check valve from the valve cover and installed a vent fitting in its place. Found another fitting designed to fit in place of the fill cap. Both have #12 AN fittings and connect to a Moroso breather tank with its own vent. So far I get very little oil or water out of it and I’m not pushing oil out of the engine gaskets.

3BFCEC68-BCA9-46A3-A456-373318193E9A.jpeg

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BBFF61D1-ECDF-45D3-A4CF-2E1771E93D04.jpeg

09C66E4E-982E-49DD-930E-0C9F4642C875.jpeg
 

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