Conclusion: PCV valve is worthless.

[Bigsyke]

So on about 3 cars so far ive been messing with my PCV valve setup. 4 catch cans and about $300 in hoses and vac blocks and 7 years later ive came to the conclusion.

The PCV valve/system is completely worthless, and is only in place to satisfy emissions.

The OEM or any high flowing 3/8ths PCV valve no matter what will NOT draw vapors from the crankcase. The crankcase is always in positive pressure. even @ idle the vacuum meets the PCV valve, and carries the pressures/vapors that were FORCED past the pcv valve. Most engines with 100+k miles will also have gasket leaks which will NEVER provide vacuum inside the crankcase.

The issue gets worse with ANY aftermarket intake, because the valve cover to intake hose does not have the flow restrictor built into it, which provides resistance to 1 direction.

The reason the PCV valve is in place is because of emissions. It is illegal to VTA, thus they needed to recycle the unburnt fume/vapors along with venting pressure. The only way they could do this in a closed system was having a restrictor to keep the static vacuum leak to a minimum, and to prevent @ 21/hg vac sucking pure oil into the intake manifold. The way it works is the PCV system is always in positive pressure, however the pressure pushes the valve open, where any slight vacuum durring cruising then sucks the vapors from the valve to be reburnt. The vacuum doesnt pull from the crankcase, it pulls before the valve. There is no way the small amount of flow the PCV valve provides can put negative pressure on the crank case when the opposite end (intake-valvecover hose/restrictor) flows about 5x as much.

blowby vapors are minimal durring vac, where the pcv valve is open and your not sucking blowby, but more oil mist. Anything after idle the pressures will force themselves past the valve, where the negative manifold pressure assists removal.

Oil contamination? None. UOA's show no more wear or fuel dilution than running with a closed system. The OEM setup is restricted for a steady idle and to prevent oil from being burned

High HP hondas use the endyn setup. 2x AN fittings in the valve cover for added pressure relief, and tap into a freeze plug on the rear of the block. If were not having the negative vac assist pulling the pressures fast the valve, then we need to have 0 positive pressure in the system.


Here is StevieC (one of the most respected members of BITOG) and a thread I made. Venting PCV and Oil contamination. - Bob Is The Oil Guy (http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1636993&gonew=1#UNREAD)

Heres another thing. The FSM states that under heavy load/high blowby where the OEM pcv cant pass the vapors through, the flow will reverse and go through the intake hose into the TB. However on a newly freshened engine with no leaks, doesnt the PCV valve close when pressure is reversed? thus another flaw clearly meaning the pressure is forced out, thus a freely flowing system is the only way to go here.

Good stuff, I hope to also on the ka24de VTA and do a UOA after 5k miles on some amsoil SSO

Heres an Audi that is venting and here is the UOA

http://pictureposter.audiworld.com/91185/uoa_2009_01-133500.jpg

[Def]

This is pretty obvious if you just look at the things.

I capped my PCV off long ago and just run a single -8 AN line to a catchcan then to a -8 AN welded bung on my intake pipe that's situated at a ~45 deg angle to the flow. Seems to be fine, and seals things up under load way better than the factory setup that breathes through a little tiny ~1/8" hole restrictor to the intake tract.

[Bigsyke]

On a FI setup it should be pretty obvious, but on an NA the myth was you needed negative vacuum in the crankcase, which is impossible.

Thanks for sharing Def, hope others share their setups or experiences.

[Def]

The vac on cruise is thought by some to "seal the rings," but like you said, it's doubtful an engine is really air tight through all the gaskets and whatnot. So you end up with a small bit of leakage that probably keeps up with the puny amount of flow the PCV valve can handle.

The flow area of a PCV valve is probably more like 3/16-1/4" in diameter at most as well, not an actual 3/8" valve.

[Bigsyke]

The vac on cruise is thought by some to "seal the rings," but like you said, it's doubtful an engine is really air tight through all the gaskets and whatnot. So you end up with a small bit of leakage that probably keeps up with the puny amount of flow the PCV valve can handle.

The flow area of a PCV valve is probably more like 3/16-1/4" in diameter at most as well, not an actual 3/8" valve.

Right, I meant the OE KA PCV valve has a 3/8ths MNPT fitting if I recall, (3/8ths for sure).

And ive tried other 3/8ths PCV valves, I think a corvette valve is a 3/8ths fitting.

[Matej]

How would you recommend to remove it?

There were a lot of arguments about it on KA-T.org.
www.ka-t.org :: View topic - HOW TO: *Properly* disconnect your PCV ... (http://www.ka-t.org/forums/viewtopic.php?t=27437&postdays=0&postorder=asc&highlight=pcv&start=0)

[projectRDM]

I do the same thing on any engine I clean up, but I weld the holes closed instead of plugging them, and just leave the valve vented to atmosphere. NA or turbo, there's a dozen or so of them running around without issue.

[Bigsyke]

I do the same thing on any engine I clean up, but I weld the holes closed instead of plugging them, and just leave the valve vented to atmosphere. NA or turbo, there's a dozen or so of them running around without issue.


Good to hear you chime in russ.

[ixfxi]

can you guys (russ or def) post pics? ide like to see the config

[S14DB]

So, you are VTA with a MAF?

[Renelovesnike]

all i have to say is DUH!!

[Johny5]

s13.4 ma motorsports valvecover with rear passenger side pcv valve in the valvecover but open vented. never a single drop or even the slightest amount of vapor has come from it. the rear driver side vent goes down to bloc kas per oem and the front driver vent goes to baffled modified kazama catch can then intake. overall this is the most successful blowby/pcv system i've seen to date for a drift car which is probably one of the most abusive cars when it comes to blowby period.

[g6civcx]

The only problem I have with VTA the PCV system is the odor. That's the only reason I recirculate.

[slidewaysmn]

Thank you, I'm sick of seeing people spend $300 plus, on them...or catch can threads

[ixfxi]

i wanna see pics guys

[EchaKqulo]

^^ Me Too....

[slider2828]

Yeah PCV's are basically junk at idle or cruising... I don't even think at high load it would make a difference at all either.... But with proper catch can setup, you can decrease crank pressure by using the negative pressure caused by the turbo. Otherwise, yeah turbo and exhaust are the biggest neg pressure you can get a car internally. Now you can always get a belt driven vac pump like nascar which pulls ridiculous amount of neg pressure based on pulley size etc...

[Jakob]

to get things right, because i think there is a lot of confustion. the crankcase pressure just gets pushed out through the valve cover to intake tube connection, beause the pcv valve on the valve cover to intake manifold connection is way to small and its just venting through the easier route?
so what i can do is just cap off the connection on the intake manifold, leave the pcv valve open and just run a catch tank from the valve cover to the intake pipe where my turbo sucks air in and so itll suck the crankcase vents in, right?
so basically i could weld the hole where the pcv valve sits on the valve cover shut and just vent it through the intake tube.

correct me if i misunderstood something. oh and pictures would be a lot more helpful then any further explanations :)

[projectRDM]

to get things right, because i think there is a lot of confustion. the crankcase pressure just gets pushed out through the valve cover to intake tube connection, beause the pcv valve on the valve cover to intake manifold connection is way to small and its just venting through the easier route?
so what i can do is just cap off the connection on the intake manifold, leave the pcv valve open and just run a catch tank from the valve cover to the intake pipe where my turbo sucks air in and so itll suck the crankcase vents in, right?
so basically i could weld the hole where the pcv valve sits on the valve cover shut and just vent it through the intake tube.

correct me if i misunderstood something. oh and pictures would be a lot more helpful then any further explanations :)

On a KA there is no PCV on the valve cover. It's just an open port, there's a bottleneck in it and people assume it's a valve. It's not. Gasses are vacuumed out on a NA application back into the intake and reburned. The problem is you're sucking that junk out and gumming up the intake manifold. I leave that port open, on older/rougher engines there is no some blowby, I've seen cars that spray a mist out the port after a hard run, but on a capable engine it's not an issue.
My main reason for deleting the PCV system is a cleaner intake manifold, you can remove the manifold after a year and it's still cleaned and shiny inside instead of being tar like.

[clark]

man i'd love to see pictures of what you guys are talking about..

also...are we talking about racing here? or should i be doing this on my SR20..

i'm a daily guy, with occasional spirited runs..

if it's only a problem when racing, then i'm not gonna do it,but if you are saying that it's negatively affecting my engine, i'll change it.

[Jakob]

On a KA there is no PCV on the valve cover. It's just an open port, there's a bottleneck in it and people assume it's a valve. It's not. Gasses are vacuumed out on a NA application back into the intake and reburned. The problem is you're sucking that junk out and gumming up the intake manifold. I leave that port open, on older/rougher engines there is no some blowby, I've seen cars that spray a mist out the port after a hard run, but on a capable engine it's not an issue.
My main reason for deleting the PCV system is a cleaner intake manifold, you can remove the manifold after a year and it's still cleaned and shiny inside instead of being tar like.
yup mine looks exactly the same , like tar that is :(

that makes total sense, the ka is N/A so there is no pressure entering the valve cover under boost through the intake manifold, thats the reason the sr has check valve in there. ok now i understand it and ill just leave the valve open or cap it off and let the other side of the valve cover ( on the turbo side) do the breathing, with a catch can connected to it. just like johny5 did, or ill just remove the pcv valve completely and block that port of and give that a try.

man i'd love to see pictures of what you guys are talking about..

also...are we talking about racing here? or should i be doing this on my SR20..

i'm a daily guy, with occasional spirited runs..

if it's only a problem when racing, then i'm not gonna do it,but if you are saying that it's negatively affecting my engine, i'll change it.

have you ever looked inside your intake manifold? its full of oil sludge and black dirt, which enters your combustion chamber sooner or later and reduces the airflow of your intake manifold because just for better emissions. the idea is to keep the intake manifold clean and still relief the crankcase pressure.

[Bigsyke]

On a FI setup you can just install barbed or AN fittings on where the OEM oil seperator is, and route the biggest line to the preturbo. Same thing with the valve cover.

FI has the easiest setup because the preturbo will have negative pressure and its easier to install a slash cut.

My problem with the PCV valve on an NA car is the restriction durring any kind of accelleration.

Or maybe the simple fact there is no negative pressure in the crank case ever, so if venting to air would get your oil dirty, so would the OEM setup. Either way the pressure forces the vapors through the valve, where the IM then sucks them up.

I already have a 5/8ths barb (3/8ths mnpt fitting) where my OEM oil seperator box is. Im going to run this to a modified greddy can behind the exhaust mani and vent there.

S14DB how would the maf readings change when your not sucking in any unmetered air? If you leave the valve cover hose connected then the readings will change but the idea is you need to vent both. Then cap or plug the TB port, along with capping the PCV tree

[s14unimog]

^That does make sense. Its senseless to have both ports when the larger one, is most likely going to vent 99% of blow by gasses. Besides under boost the valve is shut so any blow by gases would exit through your VC vent; of course referring to an SR. If you did have excess blow by at idle, where the valve would be open due to vacuum pull from the IM, then your turbo would pull that out as well. If it were excessive then you have bigger problems internally. Good discussion!

[irritatedmax]

so on a ka-t setup:

valve cover port = put a small filter on it and let it vent

pcv = hose from pcv to catch can then to the pre-turbo piping. (or you could replace the pcv with an -an fitting and run a line to a catch can then to the pre-turbo piping)

am i understanding this correctly?

[Bigsyke]

Make sure the preturbo is a slash cut, and use the largest lines possible to prevent vapor. I dont like filters on the valve cover, id run the valve cover to a seperate vented catch can. And personally I wouldnt even put a filter on it since its a restriction after a few hundred miles. Instead of a filter on the can, id run a curved hose pointing down, similar to the OEM transmission vent.

I would like to get rid of that OE black seperator box, and run a fitting directly in there, but Ive never pulled that box out to see if there is a press fit, or its even circular.

http://www.honda-tech.com/showthread.php?t=1674798&highlight=venting+atmosphere

Most of these guys arent even going to the preturbo, just vented cans.

Good read

[GSXRJJordan]

Awesome thread, bookmarked to read at home. Thanks Big for getting all the info together, I know you've been working on this for a while!

[projectRDM]

yup mine looks exactly the same , like tar that is :(

that makes total sense, the ka is N/A so there is no pressure entering the valve cover under boost through the intake manifold, thats the reason the sr has check valve in there. ok now i understand it and ill just leave the valve open or cap it off and let the other side of the valve cover ( on the turbo side) do the breathing, with a catch can connected to it. just like johny5 did, or ill just remove the pcv valve completely and block that port of and give that a try.
have you ever looked inside your intake manifold? its full of oil sludge and black dirt, which enters your combustion chamber sooner or later and reduces the airflow of your intake manifold because just for better emissions. the idea is to keep the intake manifold clean and still relief the crankcase pressure.

Don't cap it, there's still pressure on it in an NA application, a filter is fine or just turn it around backwards (the fitting is pressed in, turns easily) and run a hose out the back of the engine to dump to in case anything comes out.

Make sure the preturbo is a slash cut, and use the largest lines possible to prevent vapor. I dont like filters on the valve cover, id run the valve cover to a seperate vented catch can. And personally I wouldnt even put a filter on it since its a restriction after a few hundred miles. Instead of a filter on the can, id run a curved hose pointing down, similar to the OEM transmission vent.

That's how I do it, leave it vented or dumped into a large hose.

I hot tanked my intake manifold after welding everything closed and then swapped it to my new engine nearly two years later. It looked exactly like the day I got it back from the machine shop, still clean. I stand by the belief that if the engine is breathing cleaner air, the emissions output is therefore cleaner. If you have to reburn fuel vapor, oil vapor, and other impurities within the engine over and over, then the exhaust is that much nastier. So in theory, you're not making the emissions worse by removing those control systems because the overall output is less anyway, venting it to the atmosphere is no worse than burning it a dozen times then venting it through the exhaust.

[S14DB]

How do you account for this major vacuum leak you are installing on your car on a MAF based system?

[Bigsyke]

How do you account for this major vacuum leak you are installing on your car on a MAF based system?

So were sealing/capping off all PCV vacuum sources (ka24de = vacuum tree under the IM runners), and closing up the TB 5/8ths fitting (NA ka-24de) If anything you need to readjust the IACV and bump the idle up. Where is the vacuum leak?

[S14DB]

So were sealing/capping off all PCV vacuum sources (ka24de = vacuum tree under the IM runners), and closing up the TB 5/8ths fitting (NA ka-24de) If anything you need to readjust the IACV and bump the idle up. Where is the vacuum leak?

Out the valve cover.

[Bigsyke]

May I ask how that causes a vacuum leak if all the nipples/fittings on the intake arm/throttlebody coupler are capped off? Im talking NA ka24de here in its stock form.

[projectRDM]

How do you account for this major vacuum leak you are installing on your car on a MAF based system?

Well, since the leak is on the engine, after combustion, it doesn't matter. It's not like you have the intake side open and venting to the air.

I don't understand your thinking here. The MAF measures the airflow into the intake pipe, once that air is drawn in it only goes into the cylinder to be ignited with the fuel, it doesn't travel through the head and out the valve cover, or out the PCV.

[bejota180sx]

i would love to see pictures of a setup on a SR and a KA... great info from everyone here, another worthwhile thread on zilvia

[Bigsyke]

The only thing I need to figure out is how to prevent condensation on the colder temps. Does having a longer hose, using breather filters or having the hoses angled downwards help?

[dnguye22]

Everyone seems to have very creative approaches on figuring out the issue of the PCV "positive crankcase ventilation" valve but one thing I don"t agree with are the people who say the PCV valve is useless. The PCV valve is the reason cars today are lasting longer than cars of yesterday. Back when there was no PCV system, the blowboys would contaiminate the oil and that would reduce the oil's ability to protect the engine. Gasoline in the blowby does not mix well with oil. The PCV reduces the chance of this happening. I know the purpose of the PCV valve may seem as just for emission purposes but it also protects our engines. I learned this in my automotive class.

[mxexux]

The reliability of cars today has very little to do with pvc. Blow by is still contaminating the oil even with pvc systems. Gas does mix with oil very well thinning it out and becoming the main reseason why oil changes are needed.

[fos240]

wow. there are a lot of people with misconceptions about the pvc system.

the port on the valve cover is to allow fresh air to go into the engine. it's on the front side of the throttle plate. there is no vacuum there, ever. the pvc valve is connected to the intake manifold behind the throttle plate. as long as the throttle is closed, i.e. idle, the pvc has vacuum on it and is sucked open. it draws air through the engine from the vc port. the idea is to suck the oil vapors out of the engine.

even during cruising there is some vacuum on the intake manifold making the pvc system work. boosted engines can still benefit from pvc system. as for the vc having vapors sucked out of it, that's not possible. when the engine is pressurized from blow by, that will push vapors out of the valve cover port into the intake tube. if you put a vacuum gauge on the intake tube going to the vc, you will never see vacuum on it.

frankie

[Spring Break '92]

This has always been a big debate on KA-T.org. The SR PCV system is much more ideal for turbo, for obvious reasons. For the turbo KA the general consensus is to replace the PCV valve with a 3/8x3/8 fitting (which is precisely the same part as the PCV valve, minus the valve part), run a hose from fitting to catch can, and from catch can to pre turbo intake pipe. As for the valve cover, VTA. Thats about the best you can do short of redesigning it on your own.

[dnguye22]

The reliability of cars today has very little to do with pvc. Blow by is still contaminating the oil even with pvc systems. Gas does mix with oil very well thinning it out and becoming the main reseason why oil changes are needed.
That is very interesting. Can you shed some light on what the main purpose behind the PCV system is? Wouldn't you also think if there is a ventilation system for blowby, the gas would want to escape through the PCV which sucks the air fouled with gas vapors out? Changing the oil is part of one of the maintenance so is changing the PCV valve. Don't you think there is a correlation to the PCV valve reducing the "wear" on the oil? If you need more concrete evidence I would be happy to accomodate that request. As a word of advice, "Automotive Service" by Tim Gilles is a very helpful book when one is not too familiar with cars.


the port on the valve cover is to allow fresh air to go into the engine. it's on the front side of the throttle plate. there is no vacuum there, ever. the pvc valve is connected to the intake manifold behind the throttle plate. as long as the throttle is closed, i.e. idle, the pvc has vacuum on it and is sucked open. it draws air through the engine from the vc port. the idea is to suck the oil vapors out of the engine.
frankie
I agree with what fos240 has to say and that has been what I have been trying to point out. He stated above "the idea is to suck the oil vapors out of the engine". It lets the engine breath as well as taking out the foul air that can quickly render the oil useless. Overall, the PCV valve does have some value to it although it may seem as an emission control device. I have been taking some automotive classes last year and the PCV valve was one of the most basic yet effective implementations car manufactures have included and there is a reason. Cars manufactures are very stingy when it comes to cost, therefore if they can remove a PCV valve from every car to save them a few bucks they will. But their decision to keep it definitely should not be underestimated. There is a reason for everything on your car.

[Bigsyke]

Everyone seems to have very creative approaches on figuring out the issue of the PCV "positive crankcase ventilation" valve but one thing I don"t agree with are the people who say the PCV valve is useless. The PCV valve is the reason cars today are lasting longer than cars of yesterday. Back when there was no PCV system, the blowboys would contaiminate the oil and that would reduce the oil's ability to protect the engine. Gasoline in the blowby does not mix well with oil. The PCV reduces the chance of this happening. I know the purpose of the PCV valve may seem as just for emission purposes but it also protects our engines. I learned this in my automotive class.

The reason cars last longer are advancements in engineering and oil designs, not emission standars (actually decrease reliability with the reduction in ZDDP in our oils)

How can blowby contaminate oil? There are high detergency oils of the oil days that were suseptible to acid, and there are synthetics which blowby acids will have no affect on the TAN due to most good synthetic oils outstanding multiadditive package. Condensation is the only thing of concern, and you can easily combat that by bringing the oil up to 212*f every week or so. Fuel dilution is by idling for excassive periods, and last time I checked fuel had a much lower flash point than oil. The PCV system protects the engine by allowing pressures to excape legally, but not optimally.

The reliability of cars today has very little to do with pvc. Blow by is still contaminating the oil even with pvc systems. Gas does mix with oil very well thinning it out and becoming the main reseason why oil changes are needed.

I dont think the very very small amount of vapors would even have any affect on the oils viscrosity.

wow. there are a lot of people with misconceptions about the pvc system.

the port on the valve cover is to allow fresh air to go into the engine. it's on the front side of the throttle plate. there is no vacuum there, ever. the pvc valve is connected to the intake manifold behind the throttle plate. as long as the throttle is closed, i.e. idle, the pvc has vacuum on it and is sucked open. it draws air through the engine from the vc port. the idea is to suck the oil vapors out of the engine.

even during cruising there is some vacuum on the intake manifold making the pvc system work. boosted engines can still benefit from pvc system. as for the vc having vapors sucked out of it, that's not possible. when the engine is pressurized from blow by, that will push vapors out of the valve cover port into the intake tube. if you put a vacuum gauge on the intake tube going to the vc, you will never see vacuum on it.

Boosted engines will never ever benifit from a PCV system. that 5/8ths port on the Valve cover couldnt ever keep up. With a decent oil like redline/amsoil Im sure you could go 5-10k miles without a PCV system before changing. Redline uses moly and esters, which will coat a surface before any oil/fuel vapors would. @212*f, any moisture, fuel vapors will be flashed.


frankie

That is very interesting. Can you shed some light on what the main purpose behind the PCV system is? Wouldn't you also think if there is a ventilation system for blowby, the gas would want to escape through the PCV which sucks the air fouled with gas vapors out? Changing the oil is part of one of the maintenance so is changing the PCV valve. Don't you think there is a correlation to the PCV valve reducing the "wear" on the oil? If you need more concrete evidence I would be happy to accomodate that request. As a word of advice, "Automotive Service" by Tim Gilles is a very helpful book when one is not too familiar with cars.

I agree with what fos240 has to say and that has been what I have been trying to point out. He stated above "the idea is to suck the oil vapors out of the engine". It lets the engine breath as well as taking out the foul air that can quickly render the oil useless. Overall, the PCV valve does have some value to it although it may seem as an emission control device. I have been taking some automotive classes last year and the PCV valve was one of the most basic yet effective implementations car manufactures have included and there is a reason. Cars manufactures are very stingy when it comes to cost, therefore if they can remove a PCV valve from every car to save them a few bucks they will. But their decision to keep it definitely should not be underestimated. There is a reason for everything on your car.

Now, oil vapors. When does your oil get above 500*f? Fuel vapors. Why do people seem to think we are flooding the engine with fuel? If your leaking fuel past the rings then you need a rebuild, because either way if your leaking fuel past the rings, the fuel will mix with the oil perminately. The PCV system wouldnt even start being effective (start pulling vapors) untill your oil is above 212*f, which is about 10-20 minutes of driving.

The PCV system keeping your oil clean theory was made back when engine oil had to be changed @ 1500 miles anyway. Its another story nowdays, and your oil will lose its TBN at the same rate with or without the PCV valve, see above.


If you do decide to keep the PCV valve, it is only effective if you have a complete seal inside your crankcase (valve covers, sparkplug gaskets, PCV Orings) Or else you will have absolutely no vacuum inside the engine block, none.

[CommandoMNky]

Now,...

Blow by pressurizes the crank case. Which is bad, because excessive pressure there will blow out seals, make the engine work harder etc.

In the old days, it was vented to the atmosphere, usually just plopped out under the car. PCV valves were implemented to clean up the roads, and thusly the environment, by eliminating essentially a big oil vapor leak. Nothing more,...

If you can vent it to the atmosphere, without getting stuff in your engine, and mucking up the bottom of your car, awesome. As long as its vented in some way, nothing to worry about.

This seems like a bunch of overcomplicating a simple system IMO. And a bunch of theories. Which,...are theories.

[93superHICAS]

This has always been a big debate on KA-T.org. The SR PCV system is much more ideal for turbo, for obvious reasons. For the turbo KA the general consensus is to replace the PCV valve with a 3/8x3/8 fitting (which is precisely the same part as the PCV valve, minus the valve part), run a hose from fitting to catch can, and from catch can to pre turbo intake pipe. As for the valve cover, VTA. Thats about the best you can do short of redesigning it on your own.
pretty much bottom line right here.
all i needed to know.

[j20accord00]

i deleted the pcv on my ka-t by plugging the intake and running the hose to a catch can and just dumping it back into the intake. cleans the air and puts it right back into the motor.

I have an 03 f250 with a 6.0L diesel. its a loud, dirty ass engine. The problem i was having the most with the pcv was that i was blowing the same intercooler pipe off almost everyday during normal driving. when it came off it would through oil EVERYTHING under the hood.

I was finding oil all in the pipes, I vented it right under the truck with a 3/4 inch hose and the truck ran better, cleaner, and i havent had an spot of oil in the intercooler.

imo it seems to do more harm then good. all that blow by oil and gunk was literally caking up in the pipes, turbo, motor and was making the truck run like shit.

[mxexux]

As a word of advice, "Automotive Service" by Tim Gilles is a very helpful book when one is not too familiar with cars.

I actually already read that book like 5 years ago...Just because you are a UTI student doesn't mean you are an expert. PVC system's only purpose is for emissions.

[dnguye22]

I actually already read that book like 5 years ago...Just because you are a UTI student doesn't mean you are an expert. PVC system's only purpose is for emissions.

What defines an expert? Doesn't every expert have to start somewhere, for example by start reading books. I may not be an expert, but I am a good student and I follow the book. From what I have learned, the pcv valve has that benefit I have stated in my earlier posts.

[Bigsyke]

It has its benifits for Federal Emissions, and the tiny valve is just about the only option possible to make the system emissions friendly.

* vacuum leaks - The valve has to be restrictive enough on 99% of cars to prevent a vacuum leak.

Here is how it works on our KA24de's;

The PCV valve is on the black box connecting to the crankcase. Valve restricts enough flow to prevent vacuum leak. The opposing end of the PCV system is on the Valve cover where there is an Oriface that restricts flow for 2 reasons;

To prevent oil/blowby from being sucked into the TB at WOT
To assist at creating suction on inside the engine.

The only question is, all of the volume the pistons are displacing needs to move somewhere freely. Can this displacement of volume escape the small PCV valve opening, along with the 1/4th restrictor valve in the Valve cover hose? At any time if there is pressure build up it will leak out somewhere like your valve cover gaskets or into your sparkplug wires.

Now you can remove the Oriface in the TB coupler to assist pressure release, and replace it with a 5/8ths barbed fitting- but then you just killed the suction effect inside the engine, and now have mostly positive pressure durring idle, with only 1 effective escape via the Valve covers. The PCV valve cant vent pressure well if the Crankcase goes positive, it relies mostly on vacuum.

think about it this way or try this;

Your in a bathroom with the door shut, you smoke about 5 ciggs and the smoke fills the room. You have a decently powerful fan vent. Now seal the door off except for a small opening. The smoke will quickly move to the vent. If you did the same thing but opened the door, the smoke would not go towards the vent.

This is why having a completlely sealed engine is most important if your going to keep the PCV valve. But can the OE PCV system really vent the displacement?

[Spring Break '92]

The only question is, all of the volume the pistons are displacing needs to move somewhere freely.

THIS. By capping off the PCV rail on my IM and running a hose from a fitting to a catch can I noticed a big difference in power when in boost. The car was set up like a stock PCV system when I got it, I bought my car with a KA-T. Aside from the oil vapors escaping and emissions and all that jazz, if you have a KA-T hooked up to work like the stock system with the PCV in place, the boosted air in the IM will fight against the PCV valve and block vapors that should be escaping, not allowing any of the pressure in the crankcase escape. Every time I clean my catch can I have a build up of Yoo Hoo colored sludge on the baffle material (home HVAC filter media) and plenty of water in the bottom. Im not arguing anyone's point, I am just stating what I have found in my setup. As a matter of fact, when I have more time to be on the internet this weekend I will post the diagram I made of a design I came up on KA-T.org that would allow the IM to pull from crankcase during idle and cruising in vacuum, but also allow the turbo to suck the pressure and vapors from the crankcase under boost while using an open fitting instead of a regular PCV valve. I post there as Chozen, if anyone else is on that forum please feel free to beat me to it and post the diagram. Im busy with work up until tomorrow night.

[Bigsyke]

Ive read that thread a while back; If you could post that UOA you did, we could anaylize it - that would seriously help out alot.

Personally I dont know if I would have the PCV vent durring winter, I noticed on my pathfinder I got alot of moisture in the oil due to shutting down the vehicle, would draw in cooler vapor filled air - and would not burn it off because the oil temps wouldnt ever reach 212*f.

[fos240]

wow. you have a lot of misconceptions here.

It has its benifits for Federal Emissions, and the tiny valve is just about the only option possible to make the system emissions friendly.

* vacuum leaks - The valve has to be restrictive enough on 99% of cars to prevent a vacuum leak.

Here is how it works on our KA24de's;

The PCV valve is on the black box connecting to the crankcase. Valve restricts enough flow to prevent vacuum leak. The opposing end of the PCV system is on the Valve cover where there is an Oriface that restricts flow for 2 reasons;

To prevent oil/blowby from being sucked into the TB at WOT
To assist at creating suction on inside the engine.



this is almost absolutely incorrect. yes the pvc is on the black box you mentioned. it is restrictive by design. not to "prevent" a vacuum leak. again, the valve cover port is the not restrictive either. it allows for fresh air to enter the engine. the fresh air comes from the intake track. this same air is metered by the mafs. so if the air goes through into the valve cover, into the engine, through the pcv valve into the intake runner and gets burned up, it doesn't matter because the air was metered to begin with. the pcv valve is basically a check valve. there is a ball inside. when there is vacuum on the pcv valve, the ball gets sucked away from the orifice allowing air flow. when the throttle plate is opened to where there is no vacuum in the manifold, the ball in the pcv valve closes off the orifice. if there is any blow buy from the combustion cycle past the rings, the positive pressure will revert back out the valve cover port and go through the throttle body.

The only question is, all of the volume the pistons are displacing needs to move somewhere freely. Can this displacement of volume escape the small PCV valve opening, along with the 1/4th restrictor valve in the Valve cover hose? At any time if there is pressure build up it will leak out somewhere like your valve cover gaskets or into your sparkplug wires.



again there is no restrictor in the pvc nor the vc port.

Now you can remove the Oriface in the TB coupler to assist pressure release, and replace it with a 5/8ths barbed fitting- but then you just killed the suction effect inside the engine, and now have mostly positive pressure durring idle, with only 1 effective escape via the Valve covers. The PCV valve cant vent pressure well if the Crankcase goes positive, it relies mostly on vacuum.

this is completely wrong. there is no vacuum on the front side of the throttle body. if you don't believe this, put a vaccum gauge on the port where the vc ties in. you won't register any vacuum. there is NEVER any vacuum on the front side of the throttle body.

think about it this way or try this;

Your in a bathroom with the door shut, you smoke about 5 ciggs and the smoke fills the room. You have a decently powerful fan vent. Now seal the door off except for a small opening. The smoke will quickly move to the vent. If you did the same thing but opened the door, the smoke would not go towards the vent.

This is why having a completlely sealed engine is most important if your going to keep the PCV valve. But can the OE PCV system really vent the displacement?

again, completely sealing the engine has nothing to do with it.

but to touch on the turbo setups, the valve cover vent can't be tied to the intercooler lines cause it will pressurize the block. it can be run to the intake pipe to the turbo, but this will not put vacuum on the engine. the only thing it will do is give the pressure from blow by a place to go. also pressure from the intake manifold during boost would actually seal the pvc valve even more. people get leaks going TO the pvc because of the hoses tied under the im to the pvc. they were never designed to have positive pressure and they are old and can leak.

i don't know if many of you guys ever owned an old 70's model car or truck. but if you did, or knew someone who did, if they didn't keep up with pvc changes, the engine would sludge up. my first car was a 75 chevelle malibu. when i was 16 i replaced the 2 barrel carb with a 4 barrel carb and intake manifold. when i took the manifold off, the whole underside was caked with 1/2 of hard dried sludge. now granted it wasn't only the pvc valve. back then the oil wasn't as advanced as it is now. but if the pvc valve had been kept up with, it wouldn't have been so bad.

frankie

[Bigsyke]

wow. you have a lot of misconceptions here.



this is almost absolutely incorrect. yes the pvc is on the black box you mentioned. it is restrictive by design. not to "prevent" a vacuum leak. again, the valve cover port is the not restrictive either. it allows for fresh air to enter the engine. the fresh air comes from the intake track. this same air is metered by the mafs. so if the air goes through into the valve cover, into the engine, through the pcv valve into the intake runner and gets burned up, it doesn't matter because the air was metered to begin with. the pcv valve is basically a check valve. there is a ball inside. when there is vacuum on the pcv valve, the ball gets sucked away from the orifice allowing air flow. when the throttle plate is opened to where there is no vacuum in the manifold, the ball in the pcv valve closes off the orifice. if there is any blow buy from the combustion cycle past the rings, the positive pressure will revert back out the valve cover port and go through the throttle body.
You must have mixed up our engines with a different sort. The PCV is restrictive by design - I will not waste my time to show you why. I take it you havent installed a 3/8ths barbed fitting and ran it directly to the manifold to see what happens.....Our Nissans just have the luxury of having a MAF to meter the air, however most other vehicles are unmetered thus the reason almost all PCV valves are controlled vacuum leaks.

http://i52.photobucket.com/albums/g37/cbuettner84/1005092235.jpg

So when I was running 2 PCV valves to up the vacuum in the crankcase, I wasnt creating a vacuum leak? Indeed I was. I had to put a restriction in the IACV.

THere is not a ball in there - its a plunger, I have disected plenty, almost none have a ball in the PCV valve. Read the FSM on PCV valve operation durring idle/WOT and backfire conditions.

There is a restrictor on the OEM intake TB boot, I have one sitting 10 feet away. You probably dont know this because Ebay intakes dont have this slashcut-restrictor, which is champered specifically and offset to induce vacuum durring WOT from air rushing past the fitting. Its 5/8ths in size.

http://i52.photobucket.com/albums/g37/cbuettner84/1005092235b.jpg


again there is no restrictor in the pvc nor the vc port. Did I not just post a picture of it? The left end of the fitting is different then the right side, there is a small 1/4 in hole drilled in the center of it, and is offset and designed to create a restriction on the vacuum the IM will pull in the crankcase, prevent oil from being sucked into the TB and create a vacuum effect when on high throttle operations when the flow reverses.


this is completely wrong. there is no vacuum on the front side of the throttle body. if you don't believe this, put a vaccum gauge on the port where the vc ties in. you won't register any vacuum. there is NEVER any vacuum on the front side of the throttle body.
But wait, there is though durring high loads, its on almost EVERY FSM IVE READ. The flow reverses, thats why the fitting is angled towards the Throttle body.


again, completely sealing the engine has nothing to do with it. im going to ignore this

but to touch on the turbo setups, the valve cover vent can't be tied to the intercooler lines cause it will pressurize the block. it can be run to the intake pipe to the turbo, but this will not put vacuum on the engine. the only thing it will do is give the pressure from blow by a place to go. also pressure from the intake manifold during boost would actually seal the pvc valve even more. people get leaks going TO the pvc because of the hoses tied under the im to the pvc. they were never designed to have positive pressure and they are old and can leak.

i don't know if many of you guys ever owned an old 70's model car or truck. but if you did, or knew someone who did, if they didn't keep up with pvc changes, the engine would sludge up. my first car was a 75 chevelle malibu. when i was 16 i replaced the 2 barrel carb with a 4 barrel carb and intake manifold. when i took the manifold off, the whole underside was caked with 1/2 of hard dried sludge. now granted it wasn't only the pvc valve. back then the oil wasn't as advanced as it is now. but if the pvc valve had been kept up with, it wouldn't have been so bad.

frankie
PCV valves dont get clogged up any more with synthetics, the springs wear out, on some models the plastic becomes brittle and crumbles, but they clog up less often now with synthetic due to the higher flash point. Fuel, moisture and exhaust gases will pass with ease.

The positive pressure inside the crankcase isnt necessarily from blowby. Its the movement of the pistons displacing air. It becomes pressurized if the air can not easily move in and out of the sealed crankcase. Severe blow by is caused from rings not sealing against the walls of the cylinders. Take the amount of displacing air at one givin time, and that amount of air needs to be able to move through your hoses. I doubt anybody has come up with the formula. The air will pulsate in and out from a open venting crankcase, it will not be completely in a positive state.

In the closing statements, you didnt even put up an argument.

[PoorMans180SX]

I stand by the belief that if the engine is breathing cleaner air, the emissions output is therefore cleaner. If you have to reburn fuel vapor, oil vapor, and other impurities within the engine over and over, then the exhaust is that much nastier. So in theory, you're not making the emissions worse by removing those control systems because the overall output is less anyway, venting it to the atmosphere is no worse than burning it a dozen times then venting it through the exhaust.

That's what a catalytic converter is for. Venting crankcase gases to the air is worse than burning them and sending them to the cat.

Here's the thing guys. On a KA, you should merely run a catch-can system from the valve cover vent, then back to the intake. This will keep all the oily crap out while still letting the gases be re-burned in the intake manifold. Believe it or not, but your engine will actually make a little more power (versus venting to atmosphere) this way, as it will draw the gases out of the crankcase under acceleration.

On an SR, it's a bit more complicated, but there is a whole thread on the proper catch can setup with an S13 valve cover, and S14's you can just run catch cans from the stock vents. Always route the catch can back to your turbo, as turbo's can really suck the gases out of the crankase. This will make more power than a vented catch can.

Venting to atmosphere is really pointless.

[roboticnissan]

I knew it!!! All along

[D1S13]

I knew it!!! All along

is that so?...:drama:

VERY INFORMATIVE THREAD here. thx for info. has anybody for a thread to match the stock PCV thread for the ka?

or do you just cut and hone the pcv value and weld on a AN fitting. My local AN store could not match the exact thread pitch.

[Spring Break '92]

^^Its 3/8x3/8, if you have a thread gauge as part of a tap and dye set in SAE, you can use it to see how many threads per inch it is. I assume you want to tun SS braided hose to your catch can from the oil separator. In that case you would be needing a 3/8x3/8 fitting with thread on both ends, but I am sure that the pitch of such a fitting will not match anything AN.

[Bigsyke]

Talking to some guys and reading alot about evac systems and differentials, It seems as if Any type of Evac system wont technically vent positive pressures any better. The higher the vacuum in the block could actually mean more positive pressure inside of the engine. The evac systems are good for circulating air to aid in additional cooling, however to create "vacuum" (vs "Airflow") there would have to be a significant restriction in place on the opposite side of the vacuum source, restricted enough to put a suction on the inside of the engine block, vs just cycling air across.. This would cancel itself out, because the displacement of just 1 piston traveling downward at an unknown speed would Displace X CFM like a syringe. If the PCV valve cant move all X CFM @ unknown speed through the small oriface, the positive pressure then vents at the Valve cover. The Valve Cover oriface is restricted to 1/4" and if the total CFM of piston cant displace all of the air through both restrictions then you have a build up of pressure that is slowly vented once the rpms drop back down to normal.

It would seem like the fresh inlet would have to flow about 1/2 as much as the vacuum source/PCV valve just to create suction in the crankcase to have any effect on removing HC's. Since the sets of restrictions are in place on the KA24DE, I doubt they can displace the amount of CFM.

The Idea and goal is to get enough airflow to flow through the engine block to effectivly cycle HC's out, cool the block, Allow X CFM in or out per piston, and not have a vacuum leak.

Stock PCV;

Airflow through the engine block to cycle HC's = Yes (on OE TB boot feat. Slashcut and 5/8ths restrictor)
Cool the Block = (Yes on an OEM airbox)
Allow X CFM in or out = NO
Not have a vacuum leak = Yes.
Emissions friendly = Yes
Combustion friendly = NO
Helps Pistons rings seal = NO
Turbo friendly = NO

Header EVac

Airflow through the block to cycle HC's = Yes
Cool the Block = No (unless you run a hose to a cool location)
Allow X CFM in or out = NO
Not have a vacuum leak = Yes
Emissions friendly = No
Combustion friendly = Yes
Helps Pistons rings seal = Yes/NO (avg of 3-5" max of vac when measured on inlet end of system, possibly unable to displace X CFM due to check valve restriction)
Turbo friendly = YES

VTA

Airflow through the block to cycle HC's = No
Cool the Block = No
Allow X CFM in or out = Yes
Not have a vacuum leak = Yes
Emissions friendly = No
Combustion friendly = Yes
Helps Pistons rings seal = Yes (rings dont flutter durring displacement if Venting is sufficient)
Turbo friendly = YES

[fos240]

the cylinders are paired inners and outers. as the inside pistons go up, the outside pistons go down. the volume of block remains the same. there may be slight pulsation of the air inside the block, but it's going to be slight and just from the movement of the pistons, not from the displacing of volume from them. there is going to be more displacement of air due to blow by. rings don't seal completely. hence the reason for leak down tests.

since reading this thread and doing some more research, i have changed my mind on what i'm going to do with my built turbo engine. but i still don't think the pcv system is a waste. just not ideal on a turbo setup. if i were staying na, i'd leave the system alone.

frankie

[babowc]

So...
thread ressurection, but:

on a KA,

PCV (connected to the crankcase)= VTA
Line coming from front of the valvecover to the throttle body boot = also VTA?

[Bigsyke]

Remove PCV valve. Install 3/8ths NPT fitting in place. Run hose to ground or vented can.

Valve cover fitting. Turn it counter clockwise and run 5/8ths hose to back of engine bay and down towards tranny case...Or to a vented can.

Plug Throttle body boot fitting with 5/8ths Cap.

And obviously cap the the Vacuum tree that the PCV was connected to.

[p0onsta]

Mirrored post from Club Spirited Drive • View topic - PCV System Configuration (http://www.clubsdx.com/forums/viewtopic.php?f=6&t=831)

The main point is that the system needs to be either completely sealed or completely open, from valve cover all the way to the PCV valve ports on the intake manifold runners. Any other way would translate into a hole after the MAFS, aka loss of metered air or entry of unmetered air.

So yes, venting PCV valve without the valve and the valve cover port to atmosphere would be a proper way to do it.

Alternatively, in order to be more considerate when sitting in city traffic with pedestrians around you by avoiding foul smelling vapors, keep the OEM PCV system properly maintained, i.e. not leaking and proper valve operation.
--> If you're turbo, install a catch can between valve cover and intake tract before turbo, after MAFS.

Once the intake manifold is pressured from high load or turbo, the PCV valve shuts. The top and bottom of the crankcase are actually 1 single chamber, considering that whole timing chain area. There will be pulsating air turbulence from the movement inside the engine. This air will come out of the valve cover vent. This is by design.
--> The valve cover vent is baffled. This will separate the air from the vapors to be plumbed back. On most N/A KA applications, a catch can is not needed since the baffles will take care of the vapors.

On boost and other high intake velocity applications, a catch can is needed and can be placed between the valve cover vent and intake tract before turbo, after MAFS. The volume of air making it past the throttle body is divided amongst the various possible paths. If enough of a volume is demanded from the small valve cover opening, it will create enough pressure (vacuum in the tube) to suck in these vapors before the baffle (designed for N/A) has a chance to condense the vapors.

At the very least, the SR PCV system is set up this way. Hope this helps :)

[Bigsyke]

Ive had my system vented all summer. After switching oil grades to rotella T6, you couldnt smell any blow by if you stuck the hose up your nose.

Its clear the whole system has to be sealed when using a PCV valve. The only problem is usually the system isnt fully sealed. If oil can leak from any part of the engine, air can be sucked in, along with dirt.

I believe oil life and engine wear decreases when venting fully to the atmosphere. I have a 5/8ths hose running from the valve cover port (which is twisted towards the fuel rail) down between intake runners 2 and 3, towards the engine mount. The OEM pcv valve has a 3/8ths fitting installed, and a 1/2" hose is routed towards the clutch slave cylinder. No oil leaks out, no dirt can be sucked in, the hoses are long enough to prevent dirt, and big enough to allow pressure to travel freely both directions. The nissan PCV valve can not flow more than the oriface installed in the TB boot, along with the naturally positive state of the crankcase - therefor its impossible for there to ever be vaccum inside the crankcase.

[Walperstyle]

so, what would you recommend on a ka24det on a Map sensor plugged into the back of the intake?

[StryfeS13]

Could it go like this?
Remove PCV vacuum tree from intake, plug up the holes, run PCV tube to a catch can, and then run the valve cover breather to the other fitting of the catch can?

[Spring Break '92]

Could it go like this?
Remove PCV vacuum tree from intake, plug up the holes, run PCV tube to a catch can, and then run the valve cover breather to the other fitting of the catch can?
Fresh air needs to be introduced into the valve cover port. You would be recirculating air/vapors from the crankcase like that. The main goal is to alleviate the pressure from the crankcase and draw out the oily vapors, in which the fresh air coming into the engine from the valve cover port assists the process. At the very least, you need to vent the crankcase and vent the valve cover. But since this pollutes the oil quickly, you want to incorporate a catch can to trap the oily vapor from the crankcase and filter it out before it circulates back into your intake air/turbine inlet.

[GeneStarWindGSW]

i'll be doing this to my car soon then