Dual catch can vs catch can and breather cap

[MSP611]

What is a better option. I thought running one catch can vta with the perm pcv plate and one occ non vta was the best setup previously. I now see people running one catch can and one breather cap on their valve cover.

Does the simple 1 occ and breather cap system solve the excessive crankcase pressures?

This is the setup I thought was to be the best solution:


Any help or info clarifying will be greatly appreciated.

[radbrad]

Just replacing the oil cap for a vented cap is substantially easier than installing a second occ.

But in my case, I get a shit ton of blow by from the valve cover, so the filter would just get covered in oil in my setup. Thus I opted to add another catch can to catch the oil.

[qkrthnu2]

Leaving the valve cover vent connected to the intake is best because it allows for a slight vacuum to be pulled. The vast majority of the blow-by oil produced by these engines is in the part-throttle PCV circuit, not the WOT valve cover circuit.

I'm running a PCV plate with two outlets and two cans. My routing is in my signature; it's probably different than what most people run. I collect a little bit of WOT oil in the #2 can, even though the valve cover connection doesn't go through the can, and I don't have oil in my intake, so it seems to be working the way I envisioned.

[MSP611]

Originally Posted by qkrthnu2 Leaving the valve cover vent connected to the intake is best because it allows for a slight vacuum to be pulled. The vast majority of the blow-by oil produced by these engines is in the part-throttle PCV circuit, not the WOT valve cover circuit. I'm running a PCV plate with two outlets and two cans. My routing is in my signature; it's probably different than what most people run. I collect a little bit of WOT oil in the #2 can, even though the valve cover connection doesn't go through the can, and I don't have oil in my intake, so it seems to be working the way I envisioned.

Ya I think ima run it like my diagram I originally posted to see how it does just picked up another occ vented for this one so I'll have one of each and I should have everything now just need a perm plate.

[jdmage_mx5]

The sp63 oil cap has a float in it so when vacuum is being applied (by intake or where every) the float closes and the vacuum is created.

Just wanted to add a little bit of info to the thread.

[5doorsoffury]

The vent's filter will pull unmetered air in messing with trims slightly when the block is under vacuum during cruising. That is the only issue I see but for most NCE since it will be very minor.

If you want the best of both worlds a check valve built into the vent's filter would solve that like a vented oil cap.

If u run the vent to the connection on the TIP you wont have to worry about that nor the smell that comes with venting a CC.

My setup for the second can has the Valve cover and the post CV hose off of the block going into a TEE then into the can. The cans exit goes to the tip.

[865ms3]

i added two 10AN ports to my valve cover. running them to the ground or a vented can. ill run a standard oil cap and my sealed can between intake manifold and PCV. she will breather and no extra lines to stuff under the manifold.

[MSP611]

Originally Posted by 865ms3 i added two 10AN ports to my valve cover. running them to the ground or a vented can. ill run a standard oil cap and my sealed can between intake manifold and PCV. she will breather and no extra lines to stuff under the manifold.

do u run a modified pcv plate or u don't have to cuz u use the AN fittings fitted on the valve cover?

[865ms3]

Originally Posted by MSP611 do u run a modified pcv plate or u don't have to cuz u use the AN fittings fitted on the valve cover?

Oem plate. Line to sealed can.....can to manifold.

Then the two added breathers up top

[Realgib3]

Originally Posted by 865ms3 Oem plate. Line to sealed can.....can to manifold. Then the two added breathers up top

And I will add that IMO this is the best setup, by a pretty decent margin.

[aviator79]

I was going to add a OCC between VC and intake.
Already have one between OEM plate and IM.
I would do breathers but @Bat-man had said he gets gas smell in his car with just vented OCC or something and I didn't want that. But if no smell than I will just add the breathers in VC. How too?

[865ms3]

If you are to the point of needing extra breathers.....0fg......racecar.

[MSP611]

Originally Posted by Realgib3 And I will add that IMO this is the best setup, by a pretty decent margin.

u really think so @Realgib3; ??? if so I just need to weld on some AN fittings to my valve cover and run a vented can on tht side?

[Realgib3]

Originally Posted by MSP611 u really think so @Realgib3; ??? if so I just need to weld on some AN fittings to my valve cover and run a vented can on tht side?

Yep, I've run many different setups from single can, single can + slash cut pipe, dual pcv plate, etc etc and I this setup has been the best on every car I've seen.

You keep the stock PCV system in tact and add enough venting under boost for anyone on earth.

You just route the breather and your second VC port to your vented can. I should have a pic somewhere.

[MSP611]

Originally Posted by Realgib3 Yep, I've run many different setups from single can, single can + slash cut pipe, dual pcv plate, etc etc and I this setup has been the best on every car I've seen. You keep the stock PCV system in tact and add enough venting under boost for anyone on earth. You just route the breather and your second VC port to your vented can. I should have a pic somewhere.

Ya a pic would help of the valve cover how it's setup with the lines.... What did u mount the second occ to?

[865ms3]

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[Realgib3]

Originally Posted by MSP611 Ya a pic would help of the valve cover how it's setup with the lines.... What did u mount the second occ to?

Here's a pic of my setup last year.

[MSP611]

Originally Posted by Realgib3 Here's a pic of my setup last year.

Does Ur vent on Ur occ clear the hood?? And did u make Tht mount?

[Realgib3]

Originally Posted by MSP611 Does Ur vent on Ur occ clear the hood?? And did u make Tht mount?

Yep it clears the hood and its mounted to a factory mounting spot for AC line bracket I think.

[Voltwings]

I had @HTP; build me a custom 4" intake with 2 5/8" breather nipples that i used with my perm plate. I only ran 1 sealed OCC between my intake and block, the block to IM was left like stock.

My reasoning here was with the 6th port and E85, i wasnt worried about dirty valves, because they never really got a chance to get any carbon build up or anything. So basically, i still maintained my DD vacuum, and then could pull a massive vacuum on the VC and block with my GTx3576 / 4" intake when at WOT and not have to worry about CC pressure.


I understand this is probably beyond what most people would need to, or are willing to, do but really the only people suffering from really bad CC pressure are the ones running good size turbos or boost anyways.

I dont feel the SP63 oil cap is large enough to do anything. I have no proof, i just feel that if your CC pressure is low enough for a vent that small to help, then its not bad enough to worry about.

[MSP611]

Hmmm I think ima try the 2 nipples on the valve cover... Gotta get some welding done anyways for my cutout on my dp, a crash bar, and now the valve cover. Might have a buddy do the welding since I'm out of practice and don't have a welder anymore.

[Realgib3]

Originally Posted by MSP611 Hmmm I think ima try the 2 nipples on the valve cover... Gotta get some welding done anyways for my cutout on my dp, a crash bar, and now the valve cover. Might have a buddy do the welding since I'm out of practice and don't have a welder anymore.

And I just wanna be clear on mine I only added one -10 fitting, the other is just the stock vent on the VC.

[865ms3]

Yea i had to do two bc the stock breather would not clear manfold. Turns out that wasn't true....but oh well.


Removed stock breather...added two .

[HaXiR]

is a second CC really that useful?

[MSP611]

Well one is for cleaning Ur intake mostly and the other in the current setup we are talking about is for venting CC pressures.

[HaXiR]

So basically you use a second CC instead of a breather filter just to not have the filter get coated in oil? But either way aren't fuel trims thrown off like stated above?

[MSP611]

Originally Posted by HaXiR So basically you use a second CC instead of a breather filter just to not have the filter get coated in oil? But either way aren't fuel trims thrown off like stated above?

U use a second vented CC with lines coming from the vent on the valve cover and a custom welded AN fitting or ur choice of fitting to the other side of the CC.. As for the Fuel Trims it is very minimal amount... As for the filter I have no experience with it
(only have experience with a venturi setup) and the point of this setup is for future headroom if wanted and proven success on BT applications.

[Putin 2.3T]

Along with this I'm running a PERM plate with two -10an fittings. One line will be connected to intake where old PCV was connected, the other will run to the tank with a check valve.

[MSP611]

Originally Posted by Putin 2.3T

O u went all fancy... These are for evos right? How are u gunna run this?

[865ms3]

Here is my finished project



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[MSP611]

Hey those plastic zip ties on Ur CC lines next to Ur exh. Mani aren't gettin too hot and melting??