check valve behind pcv - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

myioz86 · 12-16-2014, 11:58 PM

Might be a good idea for all the people that are running boost to put a check valve behind the pcv valve and the crank case.last night i took the hose off and checked how easy it is for boost to leak out this inlet. there is no resistance at all and i could blow and suck air through this opening.should only be able to push air through but not come back.

in my mind this means boost can leak out and into crank case

Thanks to JAMESM who brought this to my attention with one of his old threads

I am going to put a check valve in today and do a test drive to see the difference in boost pressure with and without valve. Might even put one on the brake booster line as i dont think it is a good idea for pressure to be going into booster then when braking, booster has to go back the other way when it is under vacume. Dieaframe is flexing one way then the other.please correct me if i am wrong

Rosticles · 12-18-2014, 08:03 PM

The PCV valve will keep your crank case from accepting manifold air. When there is pressure in the manifold it closes, just like a check valve.

kbogarto · 12-18-2014, 09:16 PM

I thought the brake booster line already had a check valve in it?

King Tut · 12-19-2014, 10:47 AM

Quote:

Originally Posted by kbogarto

I thought the brake booster line already had a check valve in it?

The brake booster definitely has a check valve in it, but I am still of the opinion that our PCV or Positive Crankcase Ventilation hose off the back of the manifold has nothing in it to prevent pressurizing the crankcase with boost.

SomeoneWhoIsntMe · 12-19-2014, 10:59 AM

@King Tut how does the PCV hose connect to the intake manifold? if it attaches to a threaded hose barb fitting you can probably find an OEM PCV valve off of something else to thread in there.

seems odd that they would do that, though, nearly all the N/A cars I've seen still have a one-way PCV valve of some sort.

King Tut · 12-19-2014, 04:05 PM

Quote:

Originally Posted by SomeoneWhoIsntMe

@King Tut how does the PCV hose connect to the intake manifold? if it attaches to a threaded hose barb fitting you can probably find an OEM PCV valve off of something else to thread in there.

seems odd that they would do that, though, nearly all the N/A cars I've seen still have a one-way PCV valve of some sort.

There is a fitting that screws into the block/crankcase and then there is a molded rubber hose that goes from that fitting to the plastic fitting on the back of the intake manifold. Nobody has shown proof that there is any kind of check valve or one way valve on that fitting that screws into the block. There definitely isn't one in the hose.

DAEMANO · 12-19-2014, 04:09 PM

Subbed

SomeoneWhoIsntMe · 12-19-2014, 05:25 PM

@King Tut normally there isn't any check valve on the block, just on the intake manifold.

how are people routing their PCV hoses such that it pressurizes the crankcase?

Fizz · 12-19-2014, 08:45 PM

@King Tut when running an oil catch can for the rear PCV, does it matter if the check valve goes before or after the occ?

Would you also place a check valve on the hose that runs from crankcase vent (under the AC compressor) to the intake pipe? Mine's a sprintex setup.

King Tut · 12-21-2014, 07:09 PM

Quote:

Originally Posted by Fizz

@King Tut when running an oil catch can for the rear PCV, does it matter if the check valve goes before or after the occ?

Would you also place a check valve on the hose that runs from crankcase vent (under the AC compressor) to the intake pipe? Mine's a sprintex setup.

That depends on whether your catch can is setup to withstand boost. I wouldn't want to chance it, so I would place the check valve between the catch can and the intake manifold.

The intake pipe never sees boost, so no need to worry about a check valve on that hose.

myioz86 · 12-21-2014, 10:51 PM

since i have found out there is no check valve in the manifold and have since put one in there the boost on my car has gone up about 1.5pounds and is pulling even harder than before.now all i have to do is build a 3" mid pipe with high flow cat and see if i can get some more "boost" out of this thing "ye haa".

Tye300 · 12-22-2014, 02:09 AM

Quote:

Originally Posted by myioz86

since i have found out there is no check valve in the manifold and have since put one in there the boost on my car has gone up about 1.5pounds and is pulling even harder than before.now all i have to do is build a 3" mid pipe with high flow cat and see if i can get some more "boost" out of this thing "ye haa".

What size check valve did you use?

Target70 · 12-22-2014, 02:41 AM

Quote:

Originally Posted by Tye300

What size check valve did you use?

+1, details please

Fizz · 12-22-2014, 05:36 AM

This works fine: http://www.usplastic.com/catalog/item.aspx?sku=64175

12-16-2014, 11:58 PM	#1
myioz86 Member Join Date: May 2014 Drives: gt-86 2013 Location: cairns qld australia Posts: 71 Thanks: 0 Thanked 24 Times in 18 Posts Mentioned: 1 Post(s) Tagged: 0 Thread(s)	check valve behind pcv Might be a good idea for all the people that are running boost to put a check valve behind the pcv valve and the crank case.last night i took the hose off and checked how easy it is for boost to leak out this inlet. there is no resistance at all and i could blow and suck air through this opening.should only be able to push air through but not come back.in my mind this means boost can leak out and into crank caseThanks to JAMESM who brought this to my attention with one of his old threads I am going to put a check valve in today and do a test drive to see the difference in boost pressure with and without valve. Might even put one on the brake booster line as i dont think it is a good idea for pressure to be going into booster then when braking, booster has to go back the other way when it is under vacume. Dieaframe is flexing one way then the other.please correct me if i am wrong

12-18-2014, 09:16 PM	#3
kbogarto Senior Member Join Date: Nov 2013 Drives: 2013 BRZ limited WRB Location: Jacksonville, FL Posts: 120 Thanks: 135 Thanked 43 Times in 31 Posts Mentioned: 1 Post(s) Tagged: 0 Thread(s)	I thought the brake booster line already had a check valve in it? __________________ 92 240sx (sold), 03 350z (sold), 13 BRZ (AVO turbo)

12-19-2014, 10:59 AM	#5
SomeoneWhoIsntMe Senior Member Join Date: May 2014 Drives: 2013 Subaru BRZ Location: Pontiac, MI Posts: 313 Thanks: 187 Thanked 196 Times in 101 Posts Mentioned: 2 Post(s) Tagged: 0 Thread(s)	@King Tut how does the PCV hose connect to the intake manifold? if it attaches to a threaded hose barb fitting you can probably find an OEM PCV valve off of something else to thread in there. seems odd that they would do that, though, nearly all the N/A cars I've seen still have a one-way PCV valve of some sort. __________________ 1jz salvaged brz build thread brought to you by visconti tuning --> Pipe dreams and poor life choices

12-19-2014, 05:25 PM	#8
SomeoneWhoIsntMe Senior Member Join Date: May 2014 Drives: 2013 Subaru BRZ Location: Pontiac, MI Posts: 313 Thanks: 187 Thanked 196 Times in 101 Posts Mentioned: 2 Post(s) Tagged: 0 Thread(s)	@King Tut normally there isn't any check valve on the block, just on the intake manifold. how are people routing their PCV hoses such that it pressurizes the crankcase? __________________ 1jz salvaged brz build thread brought to you by visconti tuning --> Pipe dreams and poor life choices

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12-19-2014, 08:45 PM	#9
Fizz Senior Addict Join Date: Jan 2013 Drives: 86 GT Location: Perth, Australia Posts: 1,217 Thanks: 249 Thanked 336 Times in 215 Posts Mentioned: 12 Post(s) Tagged: 0 Thread(s)	@King Tut when running an oil catch can for the rear PCV, does it matter if the check valve goes before or after the occ? Would you also place a check valve on the hose that runs from crankcase vent (under the AC compressor) to the intake pipe? Mine's a sprintex setup.

12-21-2014, 10:51 PM	#11
myioz86 Member Join Date: May 2014 Drives: gt-86 2013 Location: cairns qld australia Posts: 71 Thanks: 0 Thanked 24 Times in 18 Posts Mentioned: 1 Post(s) Tagged: 0 Thread(s)	since i have found out there is no check valve in the manifold and have since put one in there the boost on my car has gone up about 1.5pounds and is pulling even harder than before.now all i have to do is build a 3" mid pipe with high flow cat and see if i can get some more "boost" out of this thing "ye haa".

12-22-2014, 05:36 AM	#14
Fizz Senior Addict Join Date: Jan 2013 Drives: 86 GT Location: Perth, Australia Posts: 1,217 Thanks: 249 Thanked 336 Times in 215 Posts Mentioned: 12 Post(s) Tagged: 0 Thread(s)	This works fine: http://www.usplastic.com/catalog/item.aspx?sku=64175

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