If you are really interested in knowing, I will post a full explanation of how to *properly* install breather filters (I see these things mis-installed all the time, especially on Mass Airflow Sensor cars like ours).
But to make a long story short:
--They make no horsepower whatsoever; they are an item of preventative maintenance, kinda like regular maintenance.
--They can help to prevent oil sludging in the intake manifold, if your engine/driving habits are prone to this condition.
--They are illegal as hell. Any smog station that does a visual inspection will put you on your knees and shoot you immediately upon seeing these.
--Aside from the above item, they tend to smell.

 

If you are really interested in knowing, I will post a full explanation of how to *properly* install breather filters

Please Do!!

 

Disclaimer: The following stuff is illegal. If you get caught by the smog police and sold into slavery in Mexico for your crimes, you didn't hear it from me. Seriously, this will significantly increase your car's output of raw, partially combusted, toxic as hell hydrocarbons. You're a bad person for even reading this.

OK, now that I've got that out of the way, here's how to install breather filters:
I am not going to go into a discussion of what the engine's crankcase breather system does, but it is essentially a way of getting rid of the fumes and vapors released by the oil in the pan as well as blowby from the cylinders and the expansion of the air in the crankcase as it gets hot and expands. On cars that have a MAF sensor to meter air, the crankcase system is basically sealed and doesn't allow unmetered air to get into the intake manifold. It is important to maintain this second part. On most Nissans, there are two vents that come off of the valve cover. One is the "fresh air inlet", that goes from the intake piping to the valve cover, and the other is the PCV valve, that goes from the plenum of the intake manifold to the valve cover.

--Take the two hoses off the engine.

--Remove the PCV valve and cut the flange off the end that holds in the check valve--you don't need it anymore and it will just impede the flow of fumes (which is bad). How you do this depends on the design of your particular PCV valve, but it should be obvious. If you screw up, a new valve cost about $2, so don't sweat it. You just want a hollow fitting left over.

--Reinstall the PCV valve.

--Put a breather filter on each of the two vent tubes on the valve cover (one of which should be the PCV valve).

--You now have two holes in your intake tract - one on the intake pipe and one on the manifold. Get some rubber vacuum caps from AutoZone and securely plug these two holes. Make sure they are airtight and not going to fall off. Otherwise, you have a vacuum leak and your car won't idle and will run really lean under throttle.

--Sit back, crack open a cold one, and savor the feeling of spitting in the eye of 35 years of emissions regulations.

 

Hmm..I'll have to think hard before doing this. I'm motivated because I have read that the SR20 intake can get really dirty from this.

 

I'm curious as to any benefit of this.

Just wondering if the vapors caught in the PCV system will cause any deposits in the intake. Also, how much of a problem is oil in the intake due to PCV? I know on some forced induction cars, it's a problem, but I've neevr heard of it being a problem on a N/A car that is maintained.

 

I believe se-r.net has a big write up about deposits in the intake.

 

I'm curious as to any benefit of this.

Just wondering if the vapors caught in the PCV system will cause any deposits in the intake. Also, how much of a problem is oil in the intake due to PCV? I know on some forced induction cars, it's a problem, but I've neevr heard of it being a problem on a N/A car that is maintained.

Legitimate question, cwepruk. I can't speak for recent Nissan engines (QR25DE, QG18DE, B15 version of the SR20DE), but older engines are absolutely notorious for this. The GA16 blows oil like crazy (more on this later), the SR20 does it under hard usage, and the 300ZX turbo engine does it under hard cornering (note that SCC's Project 300ZX totally re-engineered its PCV system to avoid this). My guess is that this is due to somewhat inadequate baffling in the crankcase and valve cover. As you surely know, this is all kinds of bad--oil in the intake fouls the throttle body and the sensors attached to the plenum, causing idle and stalling problems, it gums up the intake valves, and it lowers the effective octane of the fuel which can cause pinging and even detonation under some circumstances (on NA and FI cars both).
My personal experience with this goes way back. My 94 XE had idle/stalling problems almost as soon as I got it, and this was before I knew anything about cars (like, I didn't know what a camshaft was) and before I ever drove the car hard at all. My dad's solution was to blow carb cleaner through the intake, which solved the problem for a while, until it inevitably returned a month or two later. Once I learned more about cars, I figured out what the problem was, so I rerouted my crankcase breathers to a catchcan. No more problems, whatsoever. This past summer, even after a year of having the PCV bypassed, when I took the entire intake manifold off the car, it was CAKED with oil/carbon deposits from earlier in its life. It took many soakings in solvent and a lot of brushing to get it totally clean. I had no clue it was that bad, and I take good care of my car. Now, I am not an Eco-Nazi, but I think emissions standards are a good thing. I don't like running around with the PCV system open to the atmosphere, but I feel it is necessary in my case to keep my car running right--it has 160K on the odo, with bit more blowby than it should have, and so it blows quite a bit of oil through the breathers. I can't afford to rebuild the engine or get a new car just yet. I don't encourage people to do what I have done unless it is absolutely necessary. And, for what its worth, the PCV system of any car is a compromised design by nature. I think a lot of oil leaks on GA16-powered cars are due to crankcase pressurization that is directly caused by a crappy PCV system. Also, if you dig around in the B13/B14 section of this board, you will be amazed at the amount of complaints of idle/stalling problems, most of which are probably due to the PCV system blowing oil.

 

Dude please tell me where you got the catch can and the parts needed to install it. I'm wanting to do this to my new SpecV so bad right now while its got low mileage. I've looked at Nopi and Summit and JC Whitney and can't find something that I know for sure is what I need. Do you happen to have any pictures of what you did?