Civic EG

What is the purpose of a Breather and where does it go? I've seen them on cars all over the site, and I was curious as to what they are.


and, I've noticed that some cars have odd looking air intakes too. ie non-existant ones and ones that come out vertically (like big breathers) What that all about? they look so sick


Any input would be appreciated.

it has to do with the PVC system of these motors. Honda puts it there for a reason. Unless your engine is turbo'd, it would be best to leave that line from the VC to the intake, and just run a sealed catch can inline. That will prevent the blow by from entering back into your throttle body & intake, yet still have the PVC system work as Honda designed it.

When you add a turbo, the PVC system is not able to operate as honda designed it, and you will be forcing air into the valve cover under boost, which is not good for crank case ventilation. Stock motors have a vacuum at all times, after turbo is added there is vacuum sometimes, then a lot of pressure when boost at higher RPM.

Teal? You're awesome. thanks for another good, quick answer.


In the mean time, I'll just nod my head and pretend to actually understand what you said.

haha, let me know if you need me to elaborate on any of that

here's some related topics too:
http://civic-eg.com/viewtopic.php?t=733
http://civic-eg.com/viewtopic.php?t=728
http://civic-eg.com/viewtopic.php?t=495

correct me If I'm wrong.


the little tube running from the intake to the valve cover is there to relieve pressure build up in the valve cover, no?

so when there's a turbo involved, there is loads more pressure involved and so the little tube won't cut it, so people op for a breather/catch can thingy?

what purpose does that catch can serve?


(off of topic)


ITB's are DEAD sexy. but what purpose do they serve?

Breathers are a bad idea because they quickly clog with oil on the inside and then act as a plug.

First you have to understand the "air pressure" inside the intake manifold. When the throttle is closed and the engine is running, the engine is sucking air from the manifold. But only a little bit of air is leaking past the throttle screw and the IACV to keep the engine idling. So vacuum is high. When the throttle is fully open, there is no vacuum. Partial throttle is somewhere between. On a turbo or supercharged car, air is being forced in, but only when the RPMs are high enough to turn the blower or turbo fast enough. At idle and low throttle angles, there is still vacuum.

You already understand blow by gasses causing crankcase pressure. This pressure is relieved through the PCV system, and the blowby and oil vapor go through a tube to the intake manifold to be burned again. That way your car doesn't drip oil, doesn't stink, and doesn't pollute the air. But this only works if the pressure in the intake manifold is lower than the pressure in the crankcase. In other words, when the intake manifold has vacuum. Vacuum not only helps to remove the pressure, it takes a load off the pistons. If you could have vacuum all the time, you'd make more power. They even sell products for domestic engines for this very purpose.

Now it's conceivable that the pressure in the intake manifold could be higher than the crankcase, even on a stock car. To stop the intake manifold from backflowing, there is a PCV valve, which is a one way check valve that closes when pressure is higher on the intake manifold side.

Under high RPMs, the crankcase pressure exceeds the limit that the PCV system can flow. So there is a breather tube on the valve cover. In high RPMs, or when your PCV system is unfortunately clogged

I HAVE TO GO I'LL FINISH THIS WHEN I GET BACK

PCV stands for Positive Crank (or Crankcase) Ventilation btw.

I've got a catch can (two actually, but that's just for the looks), and they take up a whole lot of really filthy/smelly water from the crankcase and valve cover.
All that crap was going into my engine to be burnt again, can you imagine what 12-15yrs of that kind of pollution does to your throttle body, intake manifold, intake ports, and maybe even to the engine itself?

I've set up my catch cans in such a way that both of them breathe into the open air via a small breather filter (one per can).
But I've put stainless steel mesh into both of them, so the moist gasses coming out of the engine kinda 'bang' into the mesh, leaving the moist behind and letting the gasses out, not clogging up the breather filters and not making the engine bay extremely dirty.
That way, on a n/a motor, you could redirect the hoses back to the intake without the risk of getting the crap into your intake.
On a f/i motor the gasses have nowhere else to go than the outside atmosphere due to pressure in stead of a vacuum in the intake system.
I've got breathers on the cans for the mere reason; I wanna boost soon, so why do work twice if one way works for both n/a and f/i...

BTW, when I removed my PCV (did it on two different motors), the check valve was so clogged up it worked like a plug.
Honda might have thought it through, but after a few years it just doesn't work the way it should.

thats sum damn good onfo there stefan!

Under high RPMs, the crankcase pressure exceeds the limit that the PCV system can flow. So there is a baffled breather tube on the valve cover connected directly to the intake tube. In high RPMs, or when your PCV system is unfortunately clogged, excess crankcase pressure is pushed out into your intake tube. They use the intake tube to keep it a closed system, so you're not polluting the air, dripping oil on the ground, and you don't get that funky egg smell in the passenger cabin. Even still, this is not enough breathing for a Honda VTEC motor. So oil gets pushed past the seals and power is slightly diminished. You have the problem of blowing your spark plug wires out of the tubes. People modify the valve cover to increase the breathing capacity of the even further to prevent this problem.

The result of this unfiltered connection to the intake tube is the same as with the intake manifold connection to the PCV: effectively decreased octane, a dirty throttle body, a dirty IACV, and a dirty intake manifold.

On a turbo or supercharged vehicle, you can see there's a problem because under boost, the pressure inside the intake tube and intake manifold is going to be much higher than in the crankcase. In fact, it's going to push into the crankcase and increase the pressure. Below boost a FI car is the same as a N/A car.

So now the problem becomes "how do I re-plumb a stock N/A system when I turbo charge the car". The only way for me to explain this properly is with a diagram; unfortunately I don't have my scanner with me.

Basically you get a couple of brake booster line check valves from the junkyard. These will act as PCV valves (but much more reliably) and only allow air to flow in one direction. That way you can still take advantage of the vacuum present in the intake manifold when you're not under boost.

The pre-turbo intake tube is capable of creating vacuum (when the engine is under boost) if you weld in a slash cut tube. This line can be T'd in to the intake manifold line so that you will always have vacuum removing pressure from your crankcase.

Another option is to use a slash cut in the exhaust, but because of heat issues, this is more difficult.

You absolutely do not want any oil vapor going into the turbo, so you will use a baffled catch can that has an oil-air separator. Both the turbo line and intake manifold line can be T'd off the clean side of the catch can. This eliminates the PCV valve and increases the breathing capacity of the crankcase ventilation system.

The valve cover line should be connected to the dirty side of the catch can.

The engine block side of the PCV line is connected to the bottom of the catch can so that oil can drip back into the crankcase. People who have seen the afterbirth come out of a catchcan are understandably reluctant to have this go back into the oil pan. But there really is no problem as long as you replace your oil and oil filter regularly. It is so much better than frequently draining a catch can on a street car.

and that's why I gave you that title

both of you guys made this a really educational thread

I really appreciate all of your help guys.


I think I get the concept a litlle better now. not completely, but I've got a nice idea. proformance wise, what would be the advatages? a cleaner throttle body?

teal_dx wrote:and that's why I gave you that title

both of you guys made this a really educational thread

I noticed that! I wasn't sure how that came about. Now I know! It's favoritism because we both have green hatches...

Advantages to a breather? None. They don't work properly. Advantages to a properly set up catch can / air-oil separator? A cleaner throttle body, IACV, and intake manifold. Less chance of pre-ignition. On a turbo the advantage is that you'll have your crankcase ventilation system that will work properly instead of blowing oil past your valve cover gasket and shooting your spark plug wires out of their tubes. Slightly more power if you went through the trouble of setting up the vacuum lines with check valves as I explained.

taken from turbod16
http://www.turbod16.com/viewtopic.php?f=3&t=21257



right now that is how I am doing my catch can setup...

I have a plug for the black box freeze hole but I have yet to order AN fittings to set it up without the black box. I already notice alot of oil fumes coming out of the breather filter when I am idling. But when I went to empty my can, the oil inside was brown,milky as if water was in there too. I would imagine the water is from the open filter allowing moisture to can itself. I wouldn't want to drain that back into my oil pan..

good stuff

LowTEC-Derbo wrote:I would imagine the water is from the open filter allowing moisture to can itself. I wouldn't want to drain that back into my oil pan..

It's actually comes from inside your motor. As I mentioned in my long winded post that I could never expect anyone to read, it's fine to cycle that back into the oil system. All makes and models of cars do. It's the oil filters job to catch all the impurities.

You could get a Canton Mecca oil filter if you want to have pristine oil. It's unfortunate but true that a lot of oil bypasses the oil filter hoping to get picked up on the next pass. Especially with the cheap filters.

I'm familiar with that thread on turbo d16. The guy is doing an awesome job, but none of those diagrams are what I described. He's getting close.



http://www.5ccreations.com/pcvart.htm

http://ls1tech.com/forums/showthread.php?p=8917821