I just put a breather on my valve cover and then I came across this, and apparently this wasn't the best idea. I want to do what the FAQ below says with a catch can. How exactly does this work? Can I use any 1 way check valve for the PCV valve? I figure I'll run a line off of the valve cover, to the catch can mounted on the firewall, with the breather on that. Will that work or do I have to run the other line back to the IM? The valve goes between the valve cover and can right? Also how does the oil seperator unit on the back of the block work and what does that have to do with the PCV system? And how come on the stock can with the PCV valve on it does it have three lines, one of which goes into the firewall? Car is a 88 CRX Si with a first gen B16a. Thanks.

http://www.team-integra.net/fo...sp#14


Modified by ED9man at 9:03 PM 7/31/2006


Modified by ED9man at 9:17 PM 7/31/2006

 

All you have to do is run a hose from the valve cover to the catch can, and you can either put a breather filter on the return line nipple or route a hose back to the intake tube, I have found both ways work just as well, but it's more common to just run a breather off of the catch can.

 

What is the function of the catch can? Also at the valve cover is it supposed to suck or blow? Which way is the one way valve supposed to work? Thanks

 

anyone?

 

bump

 

Here's what I think the system does, tell me if I'm wrong. There are two seperate breather locations, on on the valve cover, and one on the back of the block. The valve cover breather doesn't have enough suck or blow to make a check valve necessary, which is why it just vents into the intake. The one of the back of the block does, and so to make sure that the pressure from the gases in there only goes one way, out, the PCV valve is used, which is on the charcoal canister, the charcoal canister cleans the vapors and sends it back into the IM to burn off. My question is, Is the vaccuum from the IM on the charcoal canister necessary to suck the vapors out of the block breather from the charcoal canister, or can I vent from the charcoal canister? Let me know if I'm wrong at all. I'm guessing that vaccuum has something to do with charcoal canister, because mine has a third line that goes into the car, which someone told me was probably a vaccuum collector. Thanks.

 

anyone?

 

The charcoal (EVAP) canister is not related to the crankcase vent system. That's for evaporation from the fuel tank.

The PCV valve isn't a simple check valve. It's also a variable restriction depending on how much vacuum it sees. The PCV valve is connected to the intake manifold. When the manifold vacuum is strong the PCV valve is very restrictive, so the flow is relatively small. When the manifold vacuum is weak (WOT) the PCV valve is not very restrictive. The goal is for the flow rate to be sorta constant with widely different manifold vacuum.

The vent line (to the intake) doesn't have a valve. Normally the air flows FROM the intake TO the valve cover, to make up for the air that's sucked out thru the PCV valve.

Under WOT or if the rings aren't real good, the blowby will overwhelm the flow rate of the PCV valve. In that case, the flow reverses thru the vent line. Oily air flows from the valve cover to the intake. In that case the catch can is useful, to trap the oil so your intake doesn't get all messy. You splice the catch can into that line.

I'm not sure why there's 2 on the valve cover and 1 on the block. Usually, there's only 2 total. You might have a newer valve cover because after some year ('97?) Honda eliminated the breather box on the block.

 

I only have one on the valve cover. My PCV valve is on the charcoal canister, but the canister is for the fuel tank? Is that the line that goes into the firewall? I'm guessing the PCV valve is just on top of that for packaging reasons. Does anything run off the breather box that I need to be concerned with? Also, where is the other PCV valve line supposed to go, the one that doesn't go to the intake. Thanks

 

I had to go look up some pictures because I wasn't sure what you were talking about.

The charcoal canister (#11) looks like it's attached to the firewall:

The PCV valve isn't part of that system.

The breather chamber (#6 below) is attached to the engine:

Your PCV valve is #7, it looks like it's just hanging on the hoses and not even attached to the breather chamber.

The vacuum from the intake manifold sucks thru the PCV valve to suck air out from the crankcase. The breather chamber acts like a catch can, separating oil from that oily air.

 

Thanks a lot, I think that clears it up, as long as the stuff is basically the same on my B16a.

 

Well I'm still a bit confused, whats the function of the cannister (#11)? specifically the portion that runs from the gas tank?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by d16_DIM &raquo;</TD></TR><TR><TD CLASS="quote">Well I'm still a bit confused, whats the function of the cannister (#11)? specifically the portion that runs from the gas tank?</TD></TR></TABLE>Cliff notes:
That's to trap evaporating gasoline so it doesn't pollute the air.

Long story:
In the 'OLD days' the gas cap had a small vent in it, so evaporating gasoline didn't cause pressure & burst the tank. Sometime around 30 years ago, the EPA decided that evaporating gasoline would 'count' as unburned hydrocarbon emmissions, so the carmakers had to do something about it.

Now, the gas tank is completely airtight. There's a vapor vent line from the top of the tank to that canister. The evaporating fuel is forced to flow out thru the canister, which is filled with activated charcoal. The gasoline is adsorbed by the charcoal, trapped.

When the engine is running, it sucks a small amount of air IN thru the canister, which evaporates the gasoline back out from the charcoal, & puts it into the intake manifold.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JimBlake &raquo;</TD></TR><TR><TD CLASS="quote">
The PCV valve isn't a simple check valve. It's also a variable restriction depending on how much vacuum it sees. The PCV valve is connected to the intake manifold. When the manifold vacuum is strong the PCV valve is very restrictive, so the flow is relatively small. When the manifold vacuum is weak (WOT) the PCV valve is not very restrictive. The goal is for the flow rate to be sorta constant with widely different manifold vacuum.

The vent line (to the intake) doesn't have a valve. Normally the air flows FROM the intake TO the valve cover, to make up for the air that's sucked out thru the PCV valve.

Under WOT or if the rings aren't real good, the blowby will overwhelm the flow rate of the PCV valve. In that case, the flow reverses thru the vent line. Oily air flows from the valve cover to the intake. In that case the catch can is useful, to trap the oil so your intake doesn't get all messy. You splice the catch can into that line.
</TD></TR></TABLE>

im in 100% agreement with jim. he's got a good understanding of whats going on. i strongly disagree with what the teamintegra blurb has to say about the filter cuasing more blowby. its conclusion is wrong.

i suggest not just leaving a filter on the valve cover. you should add a catch can, route the valvecover line to the catch can then add the filter to the catch can. thats the better way. then plug the nipple on the intake. so its my opinion that you do NOT need to keep the system closed.


Modified by Tyson at 5:27 PM 8/4/2006

 

Thanks everyone

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Tyson &raquo;</TD></TR><TR><TD CLASS="quote">i suggest not just leaving a filter on the valve cover. you should add a catch can, route the valvecover line to the catch can then add the filter to the catch can. thats the better way. then plug the nipple on the intake. so its my opinion that you do NOT need to keep the system closed.

Modified by Tyson at 5:27 PM 8/4/2006</TD></TR></TABLE>That'll work just fine, but technically it's not legal. Especially where there's strict emissions inspections.

 

Thanks that makes more sense. Does the canister require the vacume from the intake or will the pressure buildup be enough to push fumes into the cannister? I'm cleaning up the engine bay and trying to understand how much of this system is necessary...