Just curious to as what the rubber hose from the intake pipe to the valve cover on the honda is for? I had replaced it with two lil air filter things but decided to put the hose back on.

My friend kept sayin it's bad to put the hose back on cause he had a problem on his escort that the intake kept sucking oil from the head into the intake...

Just wanted to know what it's really for.

 

It's a PCV system (Positive Crankcase Ventilation).

Basically, when your engine is spinning, you get peaks of high and low pressure in the bottom end of your engine. This is bad - if the pistons are having to fight positive pressure in the bottom end, it robs you of power. The answer is just to open up the bottom end (ie, don't seal it air-tight) so that the pressure doesn't build up. The hole on your valve cover is to vent the bottom end of the engine. Engines have had ventilated crankcases for almost all of history, but up until the 60s/70s, they'd always just be vented into the air with a breather cap.

So why does it go to your intake now? Well you can't vent that into the air any more. There's all kinds of nasty oil fumes and spent crap floating around in there. Very bad for pollution. So for the last 3 decades, the government has required manufacturers to vent all those fumes back into the engine. There it gets burned cleanly.

If you have a poorly designed PCV system (like my POS Mustang), or a bad PCV valve, it can suck oil into the intake, though that's not generally a huge problem on Hondas. Most people remove the PCV valve either (a) for looks, or (b) for engine 'cleanliness'. Passing all those nasty oil fumes into the chambers to be burned hurts power a bit (I must stress a BIT - might rob you of 0.5hp, really not worth worrying). You're fine removing them, just be aware that depending on your local rules, you may or may not pass emissions, and your conscience may have issues with venting all those bad fumes into the air.

I must also stress one other point - do not, repeat, DO NOT put a breather on the intake side of the tube. Put a breather on the valve cover, but solidly PLUG the intake tube. You can do some serious damage from a lean or rich condidtion if that tube isn't air-tight downstream and around the O2 sensor.

 

So if i just put the hose back on there, i should be fine?

Yea my friend said he had a problem with oil being sucked back into the intake from his POS 93 escort..he treats as if his car and my car are of similiar production and quality..

 

Oh yeah, the hose won't hurt anything at all. Your engine will be burning all those oil fumes, so it'll run a bit 'dirtier' inside, but every Honda ever made has had a PCV like that, so clearly reliability is not an issue..... It's SUPPOSED to suck oil vapors back, that's the point. Just not too much vapor. Too much oil is bad, but that only happens with a crappy valve or crappy design (like an Escort or Mustang).

As I said, there's no real need to remove it, unless you (a) just like the looks of the breather, (b) have an *extremely* built, high-performance engine, or (c) are generally fanatical.

Just make sure the intake tube is sealed, either with the hose or by you.

 

Lmao I just noticed you bashing mustangs...but don't you drive one lol..

 

Hey I'll be the first to admit it's a piece of ****. But it goes pretty darn fast (in a straight line, at least), and most important, the ladies like it.

 

Sorry to rehash this old thread like this, but I thought this might be interesting to some people.

Here's what a poorly-implemented PCV can do. This is the upper intake manifold from a 2000 V6 Mustang, which has an extremely over-active PCV system (99 and 2000 were very bad, Ford corrected the issue mid-year in 2000). It pulls significant amounts of vapor into the intake, and deposits oil sludge in the #3 and #6 runners.

Here's the bottom of upper manifold.


Here's a closeup of the #6 long runner. Check out all that wonderful black tar the engine was choking on.


The #6 plug actually wasn't fouled too badly. Suffice it to say I will be removing the PCV system from this car shortly.

Hondas don't much have to worry about this.

 

except for preludes...ive done 2 of my friend's, a 1992 Si and a 1995 S. We had to get breathers for them both

 

So preludes have that problem?

 

True, some of the late model Preludes weren't exactly 'clean', but they're nowhere NEAR as bad as what I posted above. It usually took 100+k miles before it started to accumulate that kind of sludge. That pic from the Mustang I posted above has only 30k miles on it. Nasty.