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.

 

[Calan]

Isn't it amazing how "in the wrong direction" we can make a simple PCV setup? Little did I know that this thread would turn into 7+ pages. But I sure have seen some great ideas from it.

yeah... but through all of this, I've learned that our PCV system isn't quite as simple as a lot of people seem to think, especially once you introduce a blow-through setup and higher boost. I still see 43628746234 threads on different forums about erratic idle and screwed LTFT's... and I'd bet a large percentage of them have hacked up PCV/catch-can setups.

I think I've figured out an easy fix for mine though, while keeping the general idea. I'm going to put a vertical baffle in the can between the two filter heads, that stops just below the drain level... essentially leaving about 1/2" of oil always in the bottom. Since both sides see basically the same pressure under both boost and vacuum, this should hydraulically isolate the two sides due to air's nature to take the path of least resistance... in theory anyway.

We'll see...besides, I like tinkering and fabbing up stuff

EDIT:

Here's a cross-section diagram:

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[DSMunknown]

It was much cheaper than buying one, and you get the benefit of the filters.

I don't see the benefit of the filters. I just took both of mine off.

 

[turbosax2]

I don't see the benefit of the filters. I just took both of mine off.

To promote better filtration/settlement in an empty catch can therfore minimizing amount of oil passing right through the can.

Quote taken from here.

 

[Calan]

I haven't run it long enough to actually prove it one way or the other, but it seems logical that they would help separate oil. If they were useless, I would think all of these filters would come off the shelf as just empty bowls with a couple of fittings.

As long as they don't impede the flow... which I see no evidence of.

 

[smellmyface686]

wow man that is one sweet diy catch can. Definitely going to look into something like that here shortly. I guess it's safe to say i would need 2 for each dsm?

 

[DSMunknown]

I'm more concerned about it/them getting clogged. Have you seen the amount of shit that goes through the Husky catch cans without the filter on?! Let's just say quite a bit in a minimal amount of time.

Something similar to the photo below.

 

[turbosax2]

I'm more concerned about it/them getting clogged. Have you seen the amount of shit that goes through the Husky catch cans without the filter on?! Let's just say quite a bit in a minimal amount of time.

I'm confused on what you're saying. Do you mean that with the filter taken out, the catch can is no longer collecting crap? Then what's the purpose of the catch can?

 

[DSMunknown]

I'm confused on what you're saying. Do you mean that with the filter taken out, the catch can is no longer collecting crap? Then what's the purpose of the catch can?

My concern is the excess pressure (aka blow-by) in the crankcase not being relieved due to a clogged filter in the catch can. But we're talking about the PCV system. Still, I would rather have no filter than a completely clogged one.

 

[Calan]

My concern is the excess pressure (aka blow-by) in the crankcase not being relieved due to a clogged filter in the catch can. But we're talking about the PCV system. Still, I would rather have no filter than a clogged one.

I see your point, but the filters are sintered bronze and (I believe) around 5 micron in size. Since we are filtering air with particles small enough to remain suspended, I don't think clogging would be an issue. (especially if you blow them out every now and then).

If you have actually had them clog, by all means please correct me

And... What Eric said. If you aren't filtering the air, what's the point? (Although I guess you'd see some of the heavier particles separate due to gravity).

 

[2DSMs]

I installed the US plastics #64175 check valve between the VC and IM on both my DSM's and didn't bother with installing a catchcan. This pcv leak fix works *very* well I must say.

I noticed on Dejon's website that he offers up two check valves. The second one goes on the valve cover vent. I already have one of those sealed fuel filter catchcans like in the vfaq already installed there. Seeing that I have a couple of extra check valves I was wondering if installing another check valve inline with the valve cover vent is really necessary?

 

[GRAVEDIGGER]

I installed the US plastics #64175 check valve between the VC and IM on both my DSM's and didn't bother with installing a catchcan. This pcv leak fix works *very* well I must say.

I noticed on Dejon's website that he offers up two check valves. The second one goes on the valve cover vent. I already have one of those sealed fuel filter catchcans like in the vfaq already installed there. Seeing that I have a couple of extra check valves I was wondering if installing another check valve inline with the valve cover vent is really necessary?

I'm not understanding how a checkvalve would work on the valve cover vent. A check valve is used to let air flow one way and then "check up" and not let air flow back the other way. A check valve is a must on the pcv side, but on the vent side the air needs to be able to flow both ways. The air gets sucked into the valve cover during idle/vaccuum and gets blown out of the valve cover when under boost. So how could a check valve possibly work on the vent side.

 

[steve]

So how could a check valve possibly work on the vent side.

Badly since it would cause the crankcase to pressurize until it exceeded the manifold pressure or the dipstick popped out.

 

[2DSMs]

According to Dejon's website the purpose of the VC vent check valve is to block pressure from the intake flowing into the VC *under boost*. Can't hurt. I'm going to go ahead and install one there.

 

[steve]

According to Dejon's website the purpose of the VC vent check valve is to block pressure from the intake flowing into the VC *under boost*. Can't hurt. I'm going to go ahead and install one there.

Sure it can hurt, thats the same direction as air flows when your running under vacuum. The PVC needs to have a source to draw from to purge the vapors from the rocker cover. The Dejon setup uses the valves to try and create a vacuum in the crankcase all the time to assist the rings sealing rather than vent the bypass.

 

[romeen]

According to Dejon's website the purpose of the VC vent check valve is to block pressure from the intake flowing into the VC *under boost*. Can't hurt. I'm going to go ahead and install one there.

That really doesn't make sense if I am understanding you correctly. Under boost the high velocity air in the intake pipe (meaning pre-compressor) actually creates vacuum relative to the crankcase thus sucking air (blowby vapors) out.

Like others said, bad idea.

 

[kenamond]

Heh...I saw those check valves on their site a month or so ago and was like WTF
Kind of like the "undivided housing mod" they sell.

And in case anyone didn't catch the "this is not a good idea" coming from everyone, don't put a check valve between the VC breather and intake pipe. And if you want one between the PCV valve and IM, USPlastics sells check valves for A LOT cheaper.

Since this *is* the "Stupid PCV question" thread, I figured I'd point out that I just picked up an OEM PCV valve assuming mine was leaking after 12k miles, got home, swapped the PCV valve, let the old one cool while I did the BLT, held as good as ever, then I check the old valve, and it's still good. I dunno, but 12k for a valve isn't bad, and who knows how long it would've lasted. Maybe I'm just lucky. Atleast I have a spare now. Still don't understand why I'm getting 15mpg city and 30mpg highway (and I'm not driving it any harder than usual which isn't very hard). Could've sworn it was a boost leak. 3" turboback is in the mail

EDIT: Just realized I can't do mental math. My PCV valve was only 8k miles old.

 

[2DSMs]

I didn't bother installing it. The consensus that "it's a bad idea" is unanimous.

 

[DSMunknown]

Mack, it sounds like you're pretty lucky. Jim was complaining of the valve sticking open after 750 miles (or so). Getting 8 thousand out of yours is pretty damn good. (Jim probably wouldn't have started this thread if that was the case for him. ) And if you are thinking about throwing away the old PCV valve away, don't. Just use some Gunk Engine Brite and it'll clean it right out.

 

[kenamond]

Mack, it sounds like you're pretty lucky. Jim was complaining of the valve sticking open after 750 miles (or so). Getting 8 thousand out of yours is pretty damn good. (Jim probably wouldn't have started this thread if that was the case for him. ) And if you are thinking about throwing away the old PCV valve away, don't. Just use some Gunk Engine Brite and it'll clean it right out.

I've been daydreaming about a little "hotbox" for my PCV valve. Hook it up in some sort of solvent bath and let some weak-ass electric motor cycle fluid through it all night. Lol...all for an $8 valve. But it's fun to invent things in the brain.

My mileage issue at least got me under the hood. I've been meaning to clean the air filter and do a BLT, and I happened to be down in Santa Fe with my son a week ago, so I popped in the Mitsu dealership, picked up a PCV valve, and showed my 3-year-old the new Evo. Can't even see the damned turbo... Anyway, it got me under the hood for the first time since the last oil change. I even spent 2 hours cleaning the engine bay...it's a Zen thing...mixed in with some OCD.

 

[turboglenn]

I found this during a search, and i'm glad to see it's still alive! The one link that had the 100+ dollar check valve in it got me to thinking. Has anyone tried a "halman style" ball and spring check valve in their PCV system?

I've built a few of that style and all it really consists of is a check valve with an adjustable amount of pressure on it. So say we use a ball point ben size spring with very little resistance to let the PCV open, and then the ball closes it so that when boost comes on the ball is in the right spot to start to seal. Similar to teh regular one, but with a heavier duty spring and maybe a filter or seal that's easy to clean.

Just a thought, as i blew my dipstick once today, and then after putting it back in i spewed oil from the oil fill cap gasket, so i know it's time for a new PCV or to build something. I'm thinking i want to build something since i haven't gotten to test my no fmic w/ meth theory yet due to weather issues.

I met up with one of our other members that just moved into town,(i forget his screen name, but Dan from indiana if that helps) We had to drill out his TB because one of the plate screws stripped while he was working on putting new seals in it, but we got it done. We were in my car and everytime i tried getting on it a little, i would lose the boost guage reading, which tells me that the AFPR line is unhooked since they are together. So i was trying not to beat it once that happened, but i still had oil on the VC If i would have only had a ONE zip tie i could have layed into it real good a few times

 

[kenamond]

I found this during a search, and i'm glad to see it's still alive! The one link that had the 100+ dollar check valve in it got me to thinking. Has anyone tried a "halman style" ball and spring check valve in their PCV system?

I've built a few of that style and all it really consists of is a check valve with an adjustable amount of pressure on it. So say we use a ball point ben size spring with very little resistance to let the PCV open, and then the ball closes it so that when boost comes on the ball is in the right spot to start to seal. Similar to teh regular one, but with a heavier duty spring and maybe a filter or seal that's easy to clean.

Just a thought, as i blew my dipstick once today, and then after putting it back in i spewed oil from the oil fill cap gasket, so i know it's time for a new PCV or to build something. I'm thinking i want to build something since i haven't gotten to test my no fmic w/ meth theory yet due to weather issues.

I met up with one of our other members that just moved into town,(i forget his screen name, but Dan from indiana if that helps) We had to drill out his TB because one of the plate screws stripped while he was working on putting new seals in it, but we got it done. We were in my car and everytime i tried getting on it a little, i would lose the boost guage reading, which tells me that the AFPR line is unhooked since they are together. So i was trying not to beat it once that happened, but i still had oil on the VC If i would have only had a ONE zip tie i could have layed into it real good a few times

I don't know if that style of check valve would work or not. The PCV valve is also a metering orifice when it's open (flowing from the VC to the IM) during idle. If you change this restriction, it might tinker with the idle characteristics...or maybe it'd work fine...dunno.

 

[DSMunknown]

So me and Craig have discussed his couple of posts on page 7, and we both agree that the single collective catch can system is crap. As I have told him, I would never recommend a single can setup. After some persuasion, he concurred. Either him or I will post back on our findings with the dual catch can setup that we have in the works.

The reason why I'm looking for two other cans is because my Huskies are leaking air at the bottom nozzle and knob. I tried capping off the end with a vacuum cap and zip tie, but the gunk still seems to find its way around it. And besides attempting JB Weld or Permatex Ultra Black RTV, there's not too many options to stop the leak at the knob.

I also noticed that when I used Teflon tape on the brass barb fitting threads, the oil, fuel and crud just ate away at it. It wasn't too long before I had boost leaks at those points. So I found that Teflon paste works much better.

 

[98eclipsekidd08]

After reading this I have a dumb question but, can you remove the OEM pcv and just put a brass fitting in there and then run the catch can with a pcv check valve from that usplastics site, or is it neccesary to run the OEM pcv valve? I kind of got the "that will work" "that wont work" out of reading this thread.

 

[turbosax2]

You could use a brass fitting instead of the pcv valve but it's not ideal. Here is a good explanation why you should keep the oem pcv valve.

The reason that you should keep the stock PCV valve is because it isn't just an Off/On check valve. It has intermidate Open/Closed position as well. And the ECU incorporates that idea that in certain situations, it may be only partially open. The 2nd check valve is just meant to assist the PCV in holding back that pressure while your boosting, and also reduces the amount of pressure the catch can is seeing. It is simple on or off. So by just using that one check valve, you may experience a worse idle because it's output doesn't vary like the ecu is expecting it to.

http://www.dsmtuners.com/forums/new...hamber-catch-can-3d-design.html#post151448853

 

[98eclipsekidd08]

thanks, I will read up on that