Stupid PCV question

[FORMONTOYA]

I've gone through 2 OEM PCV (read boost leak) valves in 1500 miles since the car came off jack stands December 05. I'm tired of buying and replacing them even though they are not that expensive. I was going to pull the nipple out of the intake and put a 1/8 BSPT plug in that location and use the nipple from the intake and replace the PCV valve, however, the nipple is a press-in fit so that's out of the question. I just capped off the nipple and used the PCV valve as my nipple to "T" into the vent line going to the intake before a G-2 gas filter (catch can).

My question is why do I have to hog out the PCV valve internals? There shouldn't be a differential pressure type of thing going on, therefore the PCV valve should remain open, shouldn't it?

Below is a half-a$$ drawing of what I propose and if someone can give me a legitimate reason why it should be hogged out, I'll just order a nipple for it.

 

[chico904]

No idea man... once things go back together, I'll probably try a different method of mounting the Husky heads on a better CC, just because I like fabricating stuff and I'm cheap

I've heard of people getting good results with an off-the-shelf CC stuffed with steel wool (scotch pads) to help separate the oil.

Scotch pads...hmm never thought of that one...

 

[RipperXX]

Whats wrong with this? Keeps oily residue out of the engine and intake, while at the same time still letting the system doing it's job. I personally am going to buy one of the square shaped Greddy catch can's and open it up to try to install a filter element down the middle of it, so the below drawing is my plan. I see no reason why it wont work well.

 

[chico904]

Whats wrong with this? Keeps oily residue out of the engine and intake, while at the same time still letting the system doing it's job. I personally am going to buy one of the square shaped Greddy catch can's and open it up to try to install a filter element down the middle of it, so the below drawing is my plan. I see no reason why it wont work well.

Because of where you have the valve cover vented on the left hand side. You do not want that vented due to, blowby containing the oily residue is now going to the atmosphere, i.e. covering your engine. Connect a line form that port to the intake with some sort of filter inbetween to trap that residue. Plus, the intake helps to pull some of that blowby out, even if only a little bit.

 

[RipperXX]

In that drawing the crank case vent (left nipple on valve cover) is vented to the atmosphere so it can draw in fresh air when the PCV is open. If I had that routed to a filter and the intake manifold then it would not be possible for it to suck in fresh air and only increase the vacume under the valve cover. Possibly resulting in a similar situation as the OP.






The system has to get fresh air to work, or at least thats my understanding. I am also not worried about that line being vented because I have a hose running from it to underneath the engine. So at WOT it can vent the crank case fumes to the atmosphere that way insted of pulling them into the intake like the factory setup. Again from my understanding at idle or off throttle I think is the only time the PCV should be open, and thats when it needs to be able to pull in fresh air.

The only problem I see there is that, that air is not metered. vs stock setup, it's drawing fresh air in from the intake pipe behinde the MAS which has been counted.... hmm so thats the only problem I see with it there, which I supose with DSMLink you could compensate for.

 

[Dsmj89]

I suggest trying out my setup that i have. It's been done and i don't see a flaw or any reason why it wouldn't function good. It's been tried and tested on high hp cars that i have seen and they work good.
I don't know what husky model you are using that went bad but i bought myself a husky air compressor inline filter, 2-1/4" npt fittings and goodyear hose and ran my system from the pcv to the catch can to the intake mani.
I took off the filter from inside so the intake manifold can suck in without creating idle problems and hooked it up. I have yet to try it but i am waiting to put my turbo on and test out the new catch can. Best part is it all ran me $20 !
Link to the catch can i made:
http://www.dsmtuners.com/forums/hangout/318310-new-95-gst-5.html

 

[RipperXX]

Isn't the point of the brass piece to act as a metal filter? Otherwise thats basicly like what I am talking about, except for then what do you do with the vent on the valve cover that in stock config. goes to the intake pipe?











Seems like the dual catch can setup is the only way to not negatively effect anything. And then I still say you have to mod the catch cans so there is some type of filter in them to catch the vapor.

 

[Dsmj89]

I don't have the vc hose connected to my intake, it's vented and my car idles perfect with it like that. I have it running down to the bottom, about 2 feet from the vc port. Cleaner intake and it gets fresher air. If the idle ever starts acting up funny i'll add another catch can there. As for the metal filter, i don't think it should be that bad running with out it.

 

[RipperXX]

Well your doing the same thing as me then on the VC vent, you didn't happen to notice a slightly lower vac reading by any chance did you?

 

[Dsmj89]

Not at all. Vacuum reads the same, how about you ?

 

[RipperXX]

Can't say for sure if that's why the vac readings are lower because of that or not as there all sorts of things done at the same time. But I am going to test this to find out soon.

 

[DSMtaco]

I read through this thread a while back but decided to brush up on it, and after reading it again i caught some flaws i didn't in the past. Below is a poor illustration of a closed loop pcv system with 2 catch cans, but bear with me.

If i'm correct, the system is supposed to draw air out of the VC via intake pipe vacuum while under boost. While during idle the airflow direction changes, and it flows towards the IM.

I think we can all agree that in order for the blow by and other contaminants to be drawn out, a inlet source of fresh air has to be available. Otherwise its like sucking on a sealed container, and it does nothing other than create a vacuum.

When air is drawn out through the PCV, its source of fresh air is the breather port...this works. When under boost, airflow is flowing out the breather. On a stock setup the pcv leaks which is bad since it is a boost leak, but in terms of ventilation it is the fresh air supply. But when we introduce a check valve the PCV port can no longer supply airflow...at which point there is no flow besides the inadequate crankcase pressure.

Its almost as if another port needs to be drilled and tapped in order to supply airflow, unless i'm missing something. WTF

The blue arrows in the drawing represent airflow, which might help explain my confusion if what i'm saying doesnt make sense.

 

[steve]

If i'm correct, the system is supposed to draw air out of the VC via intake pipe vacuum while under boost. While during idle the airflow direction changes, and it flows towards the IM.

I think we can all agree that in order for the blow by and other contaminants to be drawn out, a inlet source of fresh air has to be available. Otherwise its like sucking on a sealed container, and it does nothing other than create a vacuum.

When air is drawn out through the PCV, its source of fresh air is the breather port...this works. When under boost, airflow is flowing out the breather. On a stock setup the pcv leaks which is bad since it is a boost leak, but in terms of ventilation it is the fresh air supply. But when we introduce a check valve the PCV port can no longer supply airflow...at which point there is no flow besides the inadequate crankcase pressure.

Anytime the Intake Manifold pressure is lower than the Rocker Cover/Crankcase pressure the PCV opens and the flow is from the intake to the RC to the IM.

On the stock setup the PCV doesn't leak, well it's not intended to. It's designed to open as described above and seal the rest of the time.

Anytime the pressure in the RC is higher than the pressure in the intake pipe there will be flow into the intake pipe. The source is whatever is causing the pressure in the crankcase/rocket cover.

The PCV is shouldn't ever be the source of airflow into the RC so the check valve isn't causing a problem.

Other than keep the IM clean what's the point of the catch can between the PCV and IM?

 

[DSMtaco]

Other than keep the IM clean what's the point of the catch can between the PCV and IM?

Exactly that, i figure it couldn't hurt. I know many are content with G2 filters but they have to be replaced often from the sounds of it.

 

[DSMtaco]

Another thought...Romeen, Anthony, Calan, and others have looked into the differences between intake vacuum and atmospheric pressure. I've searched for the results, but have found nothing.

Reason i bring it up, is cause lets say you have your boost set to 20psi. If your pulling air from ground zero(atmospheric pressure) than 20psi is 20psi. But if your drawing air through an intake pipe which has a vacuum of -.05 or -1psi, in order to create and hold 20psi of boost your turbo is actually pulling 21psi. Thus working harder trying to compensate for the vacuum. Now what if you introduce a sealed air box, which would fill with air when up to speed. Although minimal, the positive pressure created by the air box would level the negative pressure in the intake pipe. Theoretically making the turbo work less to obtain full boost.

These are purely conjectures. In no way am i trying to spread misinformation within this community, i'm just curious.

Now back to the subject of this thread...the pressure in the VC will flow towards the vacuum, whether it be in the IM or intake pipe. If an air box would truly eliminate the vacuum in the intake pipe, that half of the system would seize to function properly.

Am i correct in thinking this or am i messed in the head?

 

[DSMunknown]

I know many are content with G2 filters but they have to be replaced often from the sounds of it.

Oooooo. And what's that, 2 bucks every couple months or so? Scawy.

 

[DSMtaco]

yea yea yea I'd much rather pay 60 bucks for a catch can

 

[RipperXX]

As mentioned earlier though since it's a paper filter, when it gets oily its flow is seriously reduced.











I am going to do the duel catch can setup. Greddy or copy of catch can with a K&N style filter down the middle of it so the gas's and oily vapor of the rocker arm cover (valve cover to most people) has to go threw the filter to reach the intake manifold.

 

[Slippi84]

I can't believe there are so many pages about something as simple as a catch can setup . All good info though. What's even more amazing is the guy that started a thread "Dumb pcv question" is now a wiseman

 

[DSMtaco]

Can anyone shed some knowledge pertaining to post #264?

 

[Achelea]

Um, which part? His Sealed airbox idea?

Which people already do, ever see drag racing DSMs with their Right headlight out? Or on the Sheppard's 7 Second I beleive the hole on the front bumper is right into his Intake filter.

Personally, I've thought of building a heat shield around my box and putting a Naca inlet, or reversed Vents on the fender and routing the air to the back of the box. That way the Heat sheild area would be protected from engine heat, and if I'm driving in the rain, the water would get sent against the back of the air box and the rest of the air would build slight pressure in the Filter's box.

Now that I think about it, wouldn't that by definition be a RAM Air intake?

About the other part, I'm rather clueless.

 

[Empyrials]

ok i've read a lot on this Oil catch can stuff, but i can't seem to find one answer.

I'm running Blow through setup, so where do i tap the line for the VC breather? it goes VC to catch can to intake normally but since my GM MAF is right before the TB elbow what can i do? if i tap it into the elbow it'll be pressurized, i thought the whole idea was so it would NOT be pressurized.

If i run the line to the intake pipe then wont i be re-metering air that has already been metered? or am i wrong on that?

 

[2gangel90]

I have been reading as many threads as i can find about this and im just wondering if what i did is ok!
I simple bought a Fram g2 fuel filter and put between the vc and the intake pipe and it works perfectly fine I have a pic. in my profile. But what im wondering is if its correct the only thing i notice is that there is this clear moisture/lubricant like substance on my engine bay i did nothing to the PCV but i am thinking about it. Just cant decide whats right!

 

[frankenstein406]

My pcv vavle was bad so i swapped it with my donor car and its good now, cleaning the other one. Will the oil be bad cause he told me he was running it for 1000 miles.

 

[chico904]

My pcv vavle was bad so i swapped it with my donor car and its good now, cleaning the other one. Will the oil be bad cause he told me he was running it for 1000 miles.

No, the oil will not be bad. Will it be slightly dirtier than oil in an engine with a properly functioning PCV system? Yes. No need to change the oil any sooner than your next interval.

 

[#40Fan]

Sorry, guys, but I couldn't read the whole 10 pages to find out if anyone had mentioned this.

A vacuum pump can be installed on an engine, eliminating the PCV. Power can be gained from it too.

If already mentioned, sorry.