Please help with PCV system routing
Thread Starter
Burning Brakes
Joined: Nov 2006
Posts: 793
Likes: 1
Please help with PCV system routing
Im in the process of fabricating my own air bridge for my intake. My question is should the PCV hose from the valve cover be before or after the MAF sensor? I have seen it done both ways but was wondering if one was better that the other. My thinking on the matter (and by no means do I know a lot in this area) is that it should be before the MAF sensor as to only let metered air into the intake side of the motor. Any ideas?
Safety Car
Joined: Aug 2006
Posts: 4,347
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From: Apache Junction AZ
I think you guys are confusing the valley cover and the valve cover connections.
The OP asked about the valve cover connection which is the clean air side. The dirty side air is the connection from the valley cover to the TB, catch cans are connected between those two points.
BJK
The OP asked about the valve cover connection which is the clean air side. The dirty side air is the connection from the valley cover to the TB, catch cans are connected between those two points.
BJK
Last edited by 07MontRedcp; Mar 9, 2010 at 10:49 PM.
Safety Car
Joined: Aug 2006
Posts: 4,347
Likes: 25
From: Apache Junction AZ
Im in the process of fabricating my own air bridge for my intake. My question is should the PCV hose from the valve cover be before or after the MAF sensor? I have seen it done both ways but was wondering if one was better that the other. My thinking on the matter (and by no means do I know a lot in this area) is that it should be before the MAF sensor as to only let metered air into the intake side of the motor. Any ideas?
BJK
Last edited by 07MontRedcp; Mar 9, 2010 at 10:48 PM.
Thread Starter
Burning Brakes
Joined: Nov 2006
Posts: 793
Likes: 1
Your thinking is correct. You want the clean side air connection to be after the air filter and before the the MAF sensor. The problem is that the the dirty side air is retuned after the MAF and leads to oil in the intake manifold. It's more or less a closed loop, so unmetered contaminated dirty air still gets past the MAF.
BJK
BJK
Safety Car
Joined: Aug 2006
Posts: 4,347
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From: Apache Junction AZ
Thread Starter
Burning Brakes
Joined: Nov 2006
Posts: 793
Likes: 1
I will be running a TVS 2300 blower kit along with LG LT headers and ECS's blower cam. Im not necessarily stuck on the 2 can set up but I have read a few posts saying that it is better than one.
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Racer
Joined: Jan 2009
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From: Webster New York
Unless I am completely confused by the OPs question, the PCV hose running off the valve cover (passenger side) inserts into the rubber coupler between the air bridge and TB, AFTER the MAF which is in the airbridge.
Race Director
Joined: Mar 2005
Posts: 10,399
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From: Austin Texas
Im in the process of fabricating my own air bridge for my intake. My question is should the PCV hose from the valve cover be before or after the MAF sensor? I have seen it done both ways but was wondering if one was better that the other. My thinking on the matter (and by no means do I know a lot in this area) is that it should be before the MAF sensor as to only let metered air into the intake side of the motor. Any ideas?
Safety Car
Joined: Jun 1999
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From: Austin, Singapore, Kuala Lumpur, Houston, Dallas, Hong Kong, Elgin, etc.. Texas
The line to the valve cover is the fresh air line. So the air path goes from the 4 inch corrugated rubber hose after the MAF and before the throttle body to the valve cover. This is clean, filtered air going into the engine via the valve cover.
Then the polluted air is pulled out of the crank case from the valley cover to the intake manifold behind the throttle body via the short "U" shaped PCV hose. This is the line that the catch can is inserted into.
Dirty air should not be going out of the valve cover line since you have manifold vacuum pulling it the other way.
Safety Car
Joined: Aug 2006
Posts: 4,347
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From: Apache Junction AZ
Here is a very good thread on catch cans and it throughly covers the catch can and pcv topics including dual catch cans and the best size for a catch can. I would highly recommend that anyone who is interested read the entire thread post by post.
http://forums.corvetteforum.com/c6-t...cv-system.html
BJK
Last edited by 07MontRedcp; Mar 10, 2010 at 01:22 PM.
Safety Car
Joined: Jun 1999
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From: Austin, Singapore, Kuala Lumpur, Houston, Dallas, Hong Kong, Elgin, etc.. Texas
First of all, I need to clarify my earlier statement about having the the clean air connection after the the air filter and before the MAF. That's the way it is done in my highly modified setup. I have clean air connections just after the the dual K&N air filters that are in the front fender areas, the drivers side connection goes to the drivers side valve cover and the passengers side connection goes to the passenger side valve cover. I forgot about the stock setup being as Mez and moog5050 described. My car was modified when new and I never saw the stock connections.
Here is a very good thread on catch cans and it thoroughly covers the catch can and pcv topics including dual catch cans and the best size for a catch can. I would highly recommend that anyone who is interested read the entire thread post by post.
http://forums.corvetteforum.com/c6-t...cv-system.html
BJK
Here is a very good thread on catch cans and it thoroughly covers the catch can and pcv topics including dual catch cans and the best size for a catch can. I would highly recommend that anyone who is interested read the entire thread post by post.
http://forums.corvetteforum.com/c6-t...cv-system.html
BJK
However, in a forced induction situation, there will naturally be more blow-by, more crankcase pressure and dirty air could end up being pushed back into the air intake. This is why some people install a breather on the oil fill cap to vent the bad air out that way thus keeping the bad air from going into the intake. This is against emission regulations.
Therefore, to keep bad air from fouling the MAF sensor, you should consider keeping the fresh air hose connected to the air intake after the MAF and before the throttle body.
Last edited by Mez; Mar 10, 2010 at 11:10 PM.
Safety Car
Joined: Aug 2006
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From: Apache Junction AZ
For a non-forced induction car, it probably does not make much of a difference if the fresh air hose is routed before or after the MAF because the air is going one way....to the valve cover assuming the pistion rings are doing their job and the amount of blow-by is normal.
However, in a forced induction situation, there will naturally be more blow-by, more crankcase pressure and dirty air could end up being pushed back into the air intake. This is why some people install a breather on the oil fill cap to vent the bad air out that way thus keeping the bad air from going into the intake. This is against emission regulations.
Therefore, to keep bad air from fouling the MAF sensor, you should consider keeping the fresh air hose connected to the air intake after the MAF and before the throttle body.
However, in a forced induction situation, there will naturally be more blow-by, more crankcase pressure and dirty air could end up being pushed back into the air intake. This is why some people install a breather on the oil fill cap to vent the bad air out that way thus keeping the bad air from going into the intake. This is against emission regulations.
Therefore, to keep bad air from fouling the MAF sensor, you should consider keeping the fresh air hose connected to the air intake after the MAF and before the throttle body.
EDIT:Here is a link to a diagram of the setup I will use. I decided not to us a the clean side catch can but will keep the clean side check valve. http://forums.corvetteforum.com/c6-t...cv-system.html
Here is a link to thumb nail photos of my meth setup:
http://forums.corvetteforum.com/c6-t...cv-system.html
BJK
Last edited by 07MontRedcp; Mar 10, 2010 at 02:59 PM.
Instructor
Joined: Apr 2009
Posts: 193
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i suppose if i were going to re-run the line with a new set up i would run it the way the factory had it. which is after the MAF and before the TB. however you may want to consider eliminating the line all together. you can cap off the line coming from the air inlet tube and cap it off at the valve cover and add a breather on your oil fill cap. this way you do not have to worry where to run it and you allow more fresh air to make its way into your engine. also this has nothing to do with your oil catch can set up. you can run your oil catch can between your valley cover and the intake. here is how i have mine set up.
[IMG]
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Race Director
Joined: Mar 2005
Posts: 10,399
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From: Austin Texas
i suppose if i were going to re-run the line with a new set up i would run it the way the factory had it. which is after the MAF and before the TB. however you may want to consider eliminating the line all together. you can cap off the line coming from the air inlet tube and cap it off at the valve cover and add a breather on your oil fill cap. this way you do not have to worry where to run it and you allow more fresh air to make its way into your engine. also this has nothing to do with your oil catch can set up. you can run your oil catch can between your valley cover and the intake. here is how i have mine set up.
[IMG][/IMG]
[IMG]
[/IMG]Maybe keep your stock oil fill cap and valve cover line and install just for the Inspection?
Instructor
Joined: Apr 2009
Posts: 193
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also keep in mind that the breather is allowing fresh air into the motor. no fumes or blow by come out of that filter.
tks, dal
Drifting
Joined: Apr 2008
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From: Lehigh Valley Pennsylvania
For F/I I would not reconnect either the valley pan or valve cover to the fresh air stream. 
Race Director
Joined: Mar 2005
Posts: 10,399
Likes: 25
From: Austin Texas
WOT at high RPM you WILL get blow by out the breather cap, the stock PCV design doesn't function well with the increased blow by at high RPM and big throttle openings. Theres not enough intake vacuum to handle the increased blow by so it goes OUT the breather cap.
Instructor
Joined: Apr 2009
Posts: 193
Likes: 1
i am not sure what happens at WOT but i can tell you without any doubt that from idle up to 4,000 rpms that filter / filler cap is sucking in air. i have had the oil / breather cap off and had my thumb in there up to 4,000 rpm's and it is definitely drawing in a lot of air!!
i understand your point but i am still of the opinion that at WOT that intake is sucking in sooooooooo much air that the oil breather cap would still be pulling air in. but again that is my opinion as i am not sure and have never had my car at WOT in the driveway.
i will probably check it next time it is on the dyno.i can tell you that after many thousands of miles the filter is still perfectly clean and has no oil or residue in it at all. for what that is worth.