Which setup is correct?
Race Director
Joined: Mar 2005
Posts: 10,399
Likes: 26
From: Austin Texas
The breather cap on the valve cover is a Federal emissions no-no, you won't pass a visual inspection.
The line from the valley cover to behind the throttle body is the usual catch can installation, the line from the valve cover to in front of the throttle body is for "make up" air and a Federal requirement.
According to the Feds we have to route all blowby to the intake instead of releasing it to the atmosphere.
The line from the valley cover to behind the throttle body is the usual catch can installation, the line from the valve cover to in front of the throttle body is for "make up" air and a Federal requirement.
According to the Feds we have to route all blowby to the intake instead of releasing it to the atmosphere.
Moderator
Joined: Dec 2002
Posts: 40,898
Likes: 4,350
From: Lakewood Ranch, FL
The breather cap on the valve cover is a Federal emissions no-no, you won't pass a visual inspection.
The line from the valley cover to behind the throttle body is the usual catch can installation, the line from the valve cover to in front of the throttle body is for "make up" air and a Federal requirement.
According to the Feds we have to route all blowby to the intake instead of releasing it to the atmosphere.
The line from the valley cover to behind the throttle body is the usual catch can installation, the line from the valve cover to in front of the throttle body is for "make up" air and a Federal requirement.
According to the Feds we have to route all blowby to the intake instead of releasing it to the atmosphere.
Thread Starter
Pro
Joined: Mar 2006
Posts: 579
Likes: 0
They are essentially the same..In the top picture you are using a oil cap breather to supply fresh air to the crankcase. In the second picture you are using the stock line from in front of the TB to supply the fresh air. Its hard to see where the hoses on the catch can go, but the top hose on the can should be connected to the valley cover line, and the bottom hose connected to the vacuum port on the manifold behind the TB.
If the catch can hoses are hooked up correctly, then either way you are using engine vacuum to vent crankcase vapors into the intake manifold.
You may see some blow by at the oil cap breather at WOT, when manifold vacuum goes to 0.
But as far as an effective system to STOP oil from entering the intake manifold, they are basically the same..
I should have said that the bottom picture is STOCK correct, as far as installing a catch can.
If the catch can hoses are hooked up correctly, then either way you are using engine vacuum to vent crankcase vapors into the intake manifold.
You may see some blow by at the oil cap breather at WOT, when manifold vacuum goes to 0.
But as far as an effective system to STOP oil from entering the intake manifold, they are basically the same..
I should have said that the bottom picture is STOCK correct, as far as installing a catch can.
You are correct, but fortunately for me where I live they do not currently smog test at all.
Last edited by slvr76; Mar 23, 2009 at 06:27 PM.
Le Mans Master
Joined: Apr 2005
Posts: 6,277
Likes: 72
From: Boston's south shore MA
I have a "maggie supercharger and recently put on a oil breather cap. Is it affecting performance? Should I remove it and only put it on when the car is on display at cruise nites/get-togethers, etc.?
Drifting
Joined: Apr 2008
Posts: 1,955
Likes: 22
From: Lehigh Valley Pennsylvania
Of course it's not smog compliant, but neither are my headers with catless mids. Where I live it is OBD scan only, no visual, and anything under 5K miles per year is emissions exempt.
Last edited by NormWild; Mar 23, 2009 at 07:05 PM.
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Thread Starter
Pro
Joined: Mar 2006
Posts: 579
Likes: 0
No you can leave the breather, but you must cap off both nipples on the intake stream. The one before the TB and the top one behind it. I then connected the valley pan nipple (lower one under the TB) to the passenger side valve cover nipple. That way all CC vapors are vented out of the breather. I am also not running a CC. The PCV is basically a metered air leak and a closed system. If you run a catch can you should keep the system closed. If you run a breather and draw vacuum out of the valley pan or valve cover you are drawing in unmetered air through the breather, thereby throwing off A/F ratios.
Of course it's not smog compliant, but neither are my headers with catless mids. Where I live it is OBD scan only, no visual, and anything under 5K miles per year is emissions exempt.
Of course it's not smog compliant, but neither are my headers with catless mids. Where I live it is OBD scan only, no visual, and anything under 5K miles per year is emissions exempt.
Drifting
Joined: Apr 2008
Posts: 1,955
Likes: 22
From: Lehigh Valley Pennsylvania
I think I get how you have your setup laid out, but what would be wrong with running a breather, capping the passenger side valve cover nipple, capping the nipple before the TB, running the top hose on the catch can to the valley nipple, and running the bottom hose on the catch can to the nipple after the TB? I may be a little dense about this, so if this idea won't work how would you run a catch can with a breather, and how would you run one without a breather. Please be specific because I'm just getting more confused
You are pulling vacuum through the top nipple here (bottom is the Valley Pan)
and this nipple here
If you run a Breather, both these must be capped.
If you are running a CC make sure you have the hoses connected correctly. The Valley pan should go to the "inlet" and the "outlet" should go the top nipple above it (to the intake manifold).
Last edited by NormWild; Mar 23, 2009 at 07:28 PM.
Melting Slicks
Joined: May 2004
Posts: 3,017
Likes: 2
If you are running a CC, the bottom picture is correct. There is no way to pull in outside air that has not first gone through your MAF.
If you run a Breather, both these must be capped.
If you are running a CC make sure you have the hoses connected correctly. The Valley pan should go to the "inlet" and the "outlet" should go the top nipple above it (to the intake manifold).
If you run a Breather, both these must be capped.
If you are running a CC make sure you have the hoses connected correctly. The Valley pan should go to the "inlet" and the "outlet" should go the top nipple above it (to the intake manifold).
Correct..I deleted my post.Sorry for the confusion.(next time I will have two cups of coffee before trying to think)
