Alright guys, at the meet I just went to some of the guys pointed out this hose that runs from my intake to my head. They said it is possible to cap it off on the intake, and place a small filter on the head. My question is: what is the specific purpose of this line, and has anyone ever tried or heard of the above suggestion?
Heres what I'm talking about:

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That hose is called the breather hose. When you rev your engine, your intake starts pulling in air, when you let off the gas, any extra air is sent through the breather back into the intake. If you really wanted to cap the intake off, you could... but It's not really going to affect anything.

(Could be wrong about all this, but I'm almost positive.)

Also,

That is a picture of a pretty typical breather filter.
It's really just a cosmetic thing, IMO...

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I believe the filter is also used when you disconnect the breather hose so that you're not spewing used fuel and traces of oil back into your engine compartment along with that air.

Edit: here is a more in depth discussion on the breather hose. (Courtesy of PO.com)

The breather there actually pulls air into the PCV system from your air intake piping (because the air in there has already been filtered), but under some conditions small amounts of oil can get up and through that hose into your intake piping... that's why people disconnect it and then throw the filter on the valve cover. The PCV system still needs to suck in that air... and since it's not hooked into your intake piping anymore, you have to provide a filter for it so that it doesn't suck anything else in =P

Does anyone have any pictures of this? Will this enhance the performance of the engine at all? It seems that if it's spewing hot air back in to the intake, it's defeating the original purpose of the performance intake. Am I wrong?

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It's not spewing air into the intake, it's pulling air from the intake. It's part of your PCV system...

Yeah, my understanding was a bit off XD

Sorry about that!

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Ohhhhhhh ok. That makes sense.

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So thats why there has to be a filter on the vc, but the intake can be capped off. It makes sense now haha.

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*sigh* it sucks air in. you're n/a right? in that case, don't do it. you'll break the vacuum and possibly even lose power in the end. not to mention spewing out gases like that is bad.

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Here is a better discussion on the flow...

It (the direction of air flow) goes like this... Intake Piping ----->Through hose to VC----->down into your crank case------>back up and out pcv valve------>into intake manifold------>back into head to burn off any left over gasses. And it's vacuum operated... the end of the line (inside the head) pulls air from the one-way pcv valve which pulls it from the crank case which pulls it from the hose to your intake piping... get it?

Under some conditions, oil and sludge and what not will go not only out of your pcv valve... but also reverse flow back through that breather hose into your intake piping... however, it's not a huge deal... it's not like it's spraying oil into your intake like crazy....

Also.. I've read the following before (and it makes sense to me... i can't confirm it's true... but it makes sense)... putting a breather element on the valve cover and bypassing the hose that runs to your intake piping is not recommended for the following reason. Notice how that metal tube that connects the VC to the intake piping is tacked directly to a second metal tube and they are touching.... that is like that for a reason. The second metal tube doesn't transport air... it transports coolant, and the reason the two are tacked together is that your crank case isn't supposed to be sucking in ambient temperature open air... that coolant line is touching to warm the air charge before it's pulled into the crank case.

OK, thanks for the info. I'm glad I didn't try to do it yet haha.

That really cleared it up for me, thanks guys.

I was thinking, would it be possible to setup some kind of filter between the intake and the vc, to stop anything from splashing back into the intake, but still allowing the air from the intake to enter the crankcase?

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For a n/a application... completely unnecessary...

Remember... your car was designed this way... the engineers at Honda weren't just guessing =P.

I guess you could use some kind of check valve (like the same idea as the PCV valve... only lets air flow one way, not the other)...

Haha no worries bro, I'd never doubt the honda geniuses haha.

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If you're really worried about it, you could put a small catch can there
Its still really unnecessary though

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yes it is called a breather filter. I have no pics but like said above it helps to prevent oil and unused fuel from entering the intake piping. I recommend a K and N breather filter thats what I got and I love not having to replace that filter every again.

ps from the looks of your hose its really not doing its job since its collapse shut. Could be wrong but from what I see doesnt look like any air is going through that piping anyway.

i had 2 breathers but then i ran a hose

ive had two breathers on my v2 and the head since ive had my car....no problem...here is a pic

Get an oil catch can.
People cap it off to keep oil from getting into the intake manifold under spirited driving. So with that said, by putting a filter on there, you'll get oil all inside of it and you'll be buying them pretty frequently.
Been there, done that.

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I was talking to one of my Honda buddies yesterday about this because we were thinking of free mods to do, I asked him about this and he flipped lol... he said it was dyno proven that it doesnt create more power, by doing this you actually lose some...its only like 2 or 3 ponies but still every little bit counts.

do research on crankcase ventilation.

"ive had two breathers on my v2 and the head since ive had my car....no problem..."

was just wondering if you were satisfied with the V2... i was considering it but havent heard much feedback on that particular one...

^^^yeah im pretty satisfied with the v2...considering it is a short ram intake, and short rams are better for response in acceleration along with the fact of not having to worry about getting water in the engine...sounds great too, and adds a good look to the engine bay... heres a pic for you to check out how it looks...

who said they were better for response?

^^^i do not have experience with a regular cai, but ive read that because the piping in shorter in short ram intakes such as the v2, the air has less piping to travel through going into the manifold making it better for response in acceleration for the car, unlike the regular cai to which the air has to travel through twice the piping to travel through going into the manifold..."this is to my understanding between the reg. cai and short rams, in this case the v2".

Wait now I'm confused. So, neither of them has to be capped off?

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the one on the intake needs to be capped off OR have a filter on it... if it's not capped off it's going to be pulling air into the intake... so a filter will keep any nasties out.

However... it's better to just cap it off. Cuz like I said... if it's not capped off, it's gonna be pullin air through it... and the air that it's pullin through is gonna be HOT as hell right there.

Remember it's all about vacuum. When you have the intake ---> vc tube on there, the vacuum effect in the cylinder head is enough that it is pulling in air... well at idle, your throttle plate is closed, so it pulls in air through the least resistant path... which in this case is that breather tube... kinda like a bypass.

Now... when you take that breather tube off... at idle it's pulling air into the cylinder head through the hole on the VC (which you hopefully have filtered!), and there probably isn't much vacuum effect in your intake tubing since your throttle butterfly is closed. But when you hit the gas and your throttle butterfly opens up, air (obviously) starts rushing into the intake manifold, and pulling air through any opening in your intake tubing that it can (again, it's gonna take the path of least resistance), meaning not only the end of the intake piping like it would on a stock application... but also that new hole you opened up by pulling the breather hose off... so that hole needs to either be plugged or filtered to at least keep the nasties out...

Capped>filtered. I'll take no air through that hole over clean but hot ass air through that hole any day of the week.

My advice (to everyone that isn't running boost at least): Stop ****ing with your PCV systems... it has a higher potential to hurt than it does to help... There is really no advantage to doing this on a n/a application that I can see/understand (other than keeping a trivial ammount of oil out of your intake tubing). If someone can prove otherwise, I'd love to see the explanation. Honda engineers designed your PCV system to work as it was designed... they didn't design it to work with all kinds of hoses unhooked and filters thrown on there... otherwise they would have shipped it to you like that =P

i had always been wondering about this one of my friends with a 5th gen put two on his i didnt know you could do that one on intake and one on vc he said it looked cute i didnt know what to think about it lol

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why are you making it sound like that its the wrong thing to do??? like i said ive had mine of their like that and have had no problems with them at all...and have had no problems with performance

I'm not making it sound like it's a wrong thing to do... I'm making it sound like it's a completely unnecessary thing to do... and my statement was not directed at you, it was directed at mcimo who asked if "neither one of them needs to be capped off", so I gave him a straight forward answer.

yeah i was talking about rus lude00 before he edited his page...my b....but yeah, it pretty much is unnecessary...rather than just connecting the rubber tubing, you replace it with two filters, which i change twice a year....but thats my choice, cuz i like the look and doesnt really hurt anything....