Does a Valve cover breather relieve enough pressure... - Ford Mustang Forum
 
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post #1 of 11 (permalink) Old 07-14-2012 Thread Starter
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Does a Valve cover breather relieve enough pressure...

Does a Valve cover breather relieve enough pressure to keep the PVC from opening and sending oil into the air intake? Or do you still need a catch can?

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post #2 of 11 (permalink) Old 07-14-2012
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There shouldn't be pressure to relieve. That's the whole point of the positive crankcase ventilation system. The intake system pulls the vapors out of the engine and sucks them back through to burn them.

I'm not sure what effect adding a breather might have, just wanted to point out the purpose of the PCV system. Breathers allow fresh, filtered air to be pulled in while the PCV system is pulling vapors out. Not sure how this would affect the 5.0 though.

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post #3 of 11 (permalink) Old 07-14-2012 Thread Starter
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I appreciate the input but the PCV works on pressure created by the blowbye gas from the combustion and relieves the pressure and the crossflow takes the moisture and blowbye out. The breather will affect performance.
The question is will the reduce pressure cause the moisture and blowbye not to be removed?

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post #4 of 11 (permalink) Old 07-14-2012
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Quote:
Originally Posted by Blue Max View Post
,,,the PCV works on pressure created by the blowbye gas from the combustion...
That's not quite how it works. The PCV valve is a one-way valve and a calibrated orifice. The one-way valve blocks flow of air from the intake manifold to the crankcase, should the pressure in the crankcase ever fall below the pressure in the intake manifold. The valve is open whenever the pressure in the manifold is lower than the pressure in the crankcase, which is most of the time when the engine is running.

The calibrated orifice allows air to flow from the crankcase to the intake manifold. This is happening most of the time when the engine is running.

The breather you are talking about adding is actually already there on the Coyote intake - it's the driver's side vent tube. It's wide open and takes air from behind the air filter and flows it into the crankcase to replace the air that's sucked out by the mostly-open PCV valve. If you put a breather (a K&N mushroom type, for instance) on the driver's side vent, it just replaces the main air filter with the breather's filter. Other than that, those who've done it report that nothing else changes.

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post #5 of 11 (permalink) Old 07-14-2012 Thread Starter
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Quote:
Originally Posted by JAJ5Point0 View Post
That's not quite how it works. The PCV valve is a one-way valve and a calibrated orifice. The one-way valve blocks flow of air from the intake manifold to the crankcase, should the pressure in the crankcase ever fall below the pressure in the intake manifold. The valve is open whenever the pressure in the manifold is lower than the pressure in the crankcase, which is most of the time when the engine is running.

The calibrated orifice allows air to flow from the crankcase to the intake manifold. This is happening most of the time when the engine is running.

The breather you are talking about adding is actually already there on the Coyote intake - it's the driver's side vent tube. It's wide open and takes air from behind the air filter and flows it into the crankcase to replace the air that's sucked out by the mostly-open PCV valve. If you put a breather (a K&N mushroom type, for instance) on the driver's side vent, it just replaces the main air filter with the breather's filter. Other than that, those who've done it report that nothing else changes.

RGR that. I realize its the suction from the intake that will open the PCV but it's also the internal pressures from the block that will force it open too.
The aftermarket valve cover breather (CFM) says "This kit is a direct replacement for factory screw-in oil fill cap and allows unwanted crankcase pressure to exit. The proprietary internal baffle substantially reduces oil particle travel without affecting air flow".
So, if anyone is running a breather and a catch can, are you still seeing substantial oil and water in your catch can?

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post #6 of 11 (permalink) Old 07-14-2012
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The wide-open vent tube on the driver's side prevents any pressure build-up in the crankcase - as soon as there's more air in the crankcase than there is room for, it exits via the vent tube (that normally provides filtered fresh air to replace the air lost to the PCV valve operation) into the duct behind the air filter and gets sucked into the engine and burned. So, no pressure build up.

I have a catch can on my PCV valve (which sees crankcase on one side and the vacuum behind the throttle body on the other, so it's not pressurized by my blower) and it picks up about 5-6 ounces of oil and no water every 5,000 mile oil change cycle.

If you remove both the driver's side and pax side vent systems from the engine, a single breather with a catch-can will work ok, or so I've read, and there will be some slop in the catch can, depending on how tight your ring seal is.

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post #7 of 11 (permalink) Old 07-14-2012 Thread Starter
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"If you remove both the driver's side and pax side vent systems from the engine, a single breather with a catch-can will work ok, or so I've read, and there will be some slop in the catch can, depending on how tight your ring seal is."

So, is the breather even worth it?

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post #8 of 11 (permalink) Old 07-15-2012
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In my case, the answer is "no". I looked at breather options and stayed with the factory layout but added a catch can on the PCV valve hose. It's fine, the vent hoses going to the intake duct and intake manifold fittings are clean and dry and oil-free, so it's working for me.

I suppose if you have a lot of blow-by, it might be better to use a different setup, but since I don't have the problem, I can't offer any insight into solving it.

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post #9 of 11 (permalink) Old 01-16-2014
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Sorry to resurrect the dead, but the search function was used.

Quote:
The breather you are talking about adding is actually already there on the Coyote intake - it's the driver's side vent tube. It's wide open and takes air from behind the air filter and flows it into the crankcase to replace the air that's sucked out by the mostly-open PCV valve. If you put a breather (a K&N mushroom type, for instance) on the driver's side vent, it just replaces the main air filter with the breather's filter. Other than that, those who've done it report that nothing else changes.
So if you add a breather on the driver's side and cap the port from the intake, you don't need one on the other side? Would leaving the PCV valve and hose on the passenger side create a vacuum leak? This would allow for say a catch can to be used on the passenger side with a breather on the drivers side? If the driver's side is an inlet already, there should be no leak?

So if you run a breather in place of the PCV or a fill cap breather like this:



CFM Performance Billet Valve Cover Breather Kit for 2005-2013 Mustang GT & V6

you need to cap off all the valves as shown in the photo?

Looking to tidy up my engine bay some and i like the looks of the breathers versus the hoses. Engine is NA and looking at possibilities. Thanks!

Some reference images:




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Uhh...not really what you want to do there.

Breathers are fine right after you put them on there. If you beat on your car, they can spew oil all over your valve covers.

The passenger side pulls from the intake manifold, the driver's pulls from the intake tube. Manifold Vacuum is much higher than intake- intake is really just make-up air. If you leave a catch can on the passenger side, I would think you could pop a breather on the driver's without much consequence, but it would not functionally change anything. Putting a breather on the passenger side effectively deletes the PCV system.

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Quote:
Originally Posted by csamsh View Post
Uhh...not really what you want to do there.

Breathers are fine right after you put them on there. If you beat on your car, they can spew oil all over your valve covers.

The passenger side pulls from the intake manifold, the driver's pulls from the intake tube. Manifold Vacuum is much higher than intake- intake is really just make-up air. If you leave a catch can on the passenger side, I would think you could pop a breather on the driver's without much consequence, but it would not functionally change anything. Putting a breather on the passenger side effectively deletes the PCV system.
Calibrated orifice allows just enough air to leak into the intake track behind the throttle body. any more unmetered un throttled air and it would just become a vacuum leak.

i am worried the drivers side breather will clog up and suck the rear main seal lose. i guess that would be easy to tell by looking at the filter.

w/o a pcv you dont get rid of the oil smoke air in the engine crank case, so you just put baked on soot al over everything. also some say you gain a few HP by having the system spin in a slight vacuum.
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