pcv vs. open vent questions
Thread Starter
On The Tree
Joined: Dec 2008
Posts: 125
Likes: 0
From: Pittsburgh
pcv vs. open vent questions Okay so to start this is my setup.
Fast 102mm
Nick Williams 102mm Tb
Valley cover with no vent
Pass valve cover has no vent
Driver valve cover has vent in the rear
I had the stock pcv hooked up when the motor was built, but I was having major oil consumption problems, and it kept blowing the hoses off the driver valve cover and at the pcv valve.
I now have a breather filter on the rear of the driver valve cover, and a breather replacing the oil cap on pass valve cover.
That left the port on the left side of the intake where the pcv valve was, and the port on the throttle body.
I left the pcv on the intake, and put a breather on the pcv. I also put a breather on the throttle body port.
I have had absolutely 0 oil consumption since. Problem is, on cold start it tries to rev back and fourth between 3k and idle for usually 30 seconds or so, and it high idles while I'm moving and idles normal when I come to a stop.
If I have a buddy plug the Tb vent with his finger, it doesn't try to cold start like that as bad.
So should I have the intake and Tb blocked off? Or just the Tb?
Ive done my searching and I've seen tons of setups and tons of ppl arguing them.
My goal is no oil in the intake while still having ventilation.
Are there any real problems with it being just vented over being drawn out by the pcv system?
Any thoughts are appreciated. Thanks guys
Fast 102mm
Nick Williams 102mm Tb
Valley cover with no vent
Pass valve cover has no vent
Driver valve cover has vent in the rear
I had the stock pcv hooked up when the motor was built, but I was having major oil consumption problems, and it kept blowing the hoses off the driver valve cover and at the pcv valve.
I now have a breather filter on the rear of the driver valve cover, and a breather replacing the oil cap on pass valve cover.
That left the port on the left side of the intake where the pcv valve was, and the port on the throttle body.
I left the pcv on the intake, and put a breather on the pcv. I also put a breather on the throttle body port.
I have had absolutely 0 oil consumption since. Problem is, on cold start it tries to rev back and fourth between 3k and idle for usually 30 seconds or so, and it high idles while I'm moving and idles normal when I come to a stop.
If I have a buddy plug the Tb vent with his finger, it doesn't try to cold start like that as bad.
So should I have the intake and Tb blocked off? Or just the Tb?
Ive done my searching and I've seen tons of setups and tons of ppl arguing them.
My goal is no oil in the intake while still having ventilation.
Are there any real problems with it being just vented over being drawn out by the pcv system?
Any thoughts are appreciated. Thanks guys
PCV is there for a reason; I suggest you try to get it right to let it do its job. I suspect what you have now is unmetered air into the intake tract(at the intake and/or throttle body) and that's basically a vacuum leak. This will cause funny idle issues at very least. PCV should apply intake manifold(read: behind the throttle blade; the port on the intake) vacuum to the PCV system resulting in vacuum in the engine. The vent side that allows fresh air back into the engine(to keep nasty blow-by crap from building up) should come from a source between the throttle blade and the MAF(likely the port on the TB but blow into it and verify). This way the additional air going into the intake has to go through the MAF to be metered and the PCM has an accurate accounting of how much air is coming into the engine. Otherwise like I said, it's basically a vacuum leak and the PCM will try to compensate but that results in idle issues.
Did you try a proper catch can? I assumed you are still running a MAF. Are you?
It occurs to me that if you set up the PCV correctly as indicated above with a catch can, you should keep your engine clean and not have oil in your intake. If you are building so much crankcase pressure that you are blowing the PCV system apart, something is plumbed wrong or you have excessive blow-by..or boost but I don't see that in your sig.
Now if you can get PCV hooked up right with a catch and such, it seems that to overcome the excessive pressure issue you could T off the PCV line or the vent line and put some type of one-way valve there(a PCV of sorts?) that would vent during times of excessive pressure but close up during times of vacuum in the PCV system. Maybe even a different PCV valve with a weaker spring. Haven't thought that all the way though but it would basically be a tiny blow off valve.
Did you try a proper catch can? I assumed you are still running a MAF. Are you?
It occurs to me that if you set up the PCV correctly as indicated above with a catch can, you should keep your engine clean and not have oil in your intake. If you are building so much crankcase pressure that you are blowing the PCV system apart, something is plumbed wrong or you have excessive blow-by..or boost but I don't see that in your sig.
Now if you can get PCV hooked up right with a catch and such, it seems that to overcome the excessive pressure issue you could T off the PCV line or the vent line and put some type of one-way valve there(a PCV of sorts?) that would vent during times of excessive pressure but close up during times of vacuum in the PCV system. Maybe even a different PCV valve with a weaker spring. Haven't thought that all the way though but it would basically be a tiny blow off valve.
Thread Starter
On The Tree
Joined: Dec 2008
Posts: 125
Likes: 0
From: Pittsburgh
I'm assuming it is due to excessive blowby, even though there's only 2k on the build. I have not ran anything but the stock pcv system and open vent. The port that WOULD be maf metered (yes I still run a maf) was moved to a breather on the side of my air box as I have a Volant cai. I also forgot to mention when the pcv was still on the car, anything over half open throttle, it would blow a puff of greyish blueish smoke from the exhaust when I'd let out to shift. This also was completely eliminated when I went open ventilation. I just tried pluggin both the manifold and the Tb, I didn't drive it, but it sure seemed to cold start a lot happier.
So have you tried a catch can in the PCV vacuum line? Should separate the oil vapor out and keep your intake clean/er. My old intake would drip oil all over my garage floor when I removed it..got a decent(http://catchcans.com/) catch can and seems to be keeping my intake clean.
IMO, it sound like your issue is way too much blow by. Furthermore by just vent the pressure a lot of the blow-by contaminates will remain in the crank case and build up in short order drastically shorting engine bearing life. IMO, either fix the blow-by issue or plan on doing oil changes every 500 miles if you want any engine life.
IMO, it sound like your issue is way too much blow by. Furthermore by just vent the pressure a lot of the blow-by contaminates will remain in the crank case and build up in short order drastically shorting engine bearing life. IMO, either fix the blow-by issue or plan on doing oil changes every 500 miles if you want any engine life.
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Thread Starter
On The Tree
Joined: Dec 2008
Posts: 125
Likes: 0
From: Pittsburgh
It doesn't go anywhere very often. I've done oil changes every 500-1000 miles since the build. Closer to 500 if its seen track or street abuse in those miles. The oil always looks great with or without pcv lol
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Verdad Gallardo Fixing the blow-by is definitely the *right* way but what do you think of the idea of some sort of small blow-off in the PCV vent line(with PCV hooked up right) as a band-aid until a re-ring? Or are you picturing some other way to fix the blow-by without tearing the engine down? Is it worth trying thicker oil or does that even affect ring seal at all?
Mighty Mouse and RX both already have 1way valve/breather solution, or DIY .
Thread Starter
On The Tree
Joined: Dec 2008
Posts: 125
Likes: 0
From: Pittsburgh
Imo, I'd recommend a one way valve inline with a breathe filter even a N.A. engine that doesn't have excessive blow-by, since you'll still get a little momentary positive crank case pressure like when taking your foot off the gas pedal while in 4th gear at the end of a 1/4 mile run in a M6 transmission car.
Mighty Mouse and RX both already have 1way valve/breather solution, or DIY .
Mighty Mouse and RX both already have 1way valve/breather solution, or DIY .
You'll have to go to MightMouse Solution website fro his breather/1 way valve or contact the WS6store since they carry his products.
http://www.ws6project.com/user_stor/..._find_part.php
http://www.ws6project.com/user_stor/...cturers_id=353
You can get the RX Performance breather/1 way valve at Colorado Speed.
http://www.coloradospeed.com/rx-perf...7qu1bt93sc8op2
http://www.ws6project.com/user_stor/..._find_part.php
http://www.ws6project.com/user_stor/...cturers_id=353
You can get the RX Performance breather/1 way valve at Colorado Speed.
http://www.coloradospeed.com/rx-perf...7qu1bt93sc8op2
Between the dirty air outlet (valve cover or LS6 valley cover port) and intake manifold passenger side inlet when using a MM catch can that has the breathe/1 way valve on his catch cans, or mounted in the oil fill cap location as a breathe /1 way valve combo. Otherwise almost the same as stock routing. FYI, when under vacuum the valve is closed.
Think I'm goin the rx setup even though the M.M. Looks cooler lol