Connecting the PCV valve to an air/oil separator catch-can

[Talamascan]

Considering my history of problems with carbon buildup around my valves and resultant significant and unacceptable detonation, I'm considering eliminating further venting of crankcase gases and oil into my intake manifold by hooking my PCV valve to a catch-can to separate out the waste oil and vent air to the atmosphere via a filter.

I know the catch-can will need to be emptied fairly often and that the procedure can incease underhood stink if not done correctly, but does anyone have any other negative or positive experiences to relay as to this idea?

[Talamascan]

Just figured out that we have one valve per bank. How annoying, but I'm still interested in blocking both from spewing further crap into my intake manifold. It's also interesting that the ecu does not appear to monitor either one, since there is no provision for either a CEL or code if one goes MIA.

[J30tChumpCar]

I have 12 cyl j30/300z heads just pulled from 6 engines (of very different lifestyles from racecar to DD to turbo to blown up 2 different ways), carbon on the valves was present but a non issue on all of them, the only place I found odd deposits were 2 of the passenger side pistons of a couple engines still not a issue but noteworthy.
Unless you have bad compression rings(unlikely) or are running on a high G-force track with hard right handers the PCV system works decently enough, replace the PCV valves and be done otherwise the lack of a PCV system can cause moisture/sludge/acidic changes to the oil which in the long term cause other more serious issues like hard to fix oil leaks or plugged oil pump inlet screens.

Sounds like you need to romp this thing a little more often

[yodawill2000]

Indeed ^^^^
I read a post from Q45TECH and he said going to redline a few times a week is good for blowing crude out.
I have a long stretch of nothing on the way home and I leave it in second and bounce off the redline a few times.
I can smell the crap its burning off every time.
If your oil is due for a change I wouldn't suggest it though.

[Talamascan]

I think that both of you have some good advice. The catch-can seems like a problematic "solution." I bought this car from the original, little old man owner, who probably never once floored it in 98,000 miles and, living on Oahu, I also rarely have an opportunity to floor it these days.

I like the idea of holding it in 2nd and pouncing off red line a few times to clear things out and I'll give it a try on a nice stretch of road near Sandy Beach/Koko Crater that used to be a popular scene for street racing back in the day when none of us had any sense.

[riaazfr1]

I don't think there is anything negative about it. I have a 2010 sentra Spec V and just bought an air breather. pretty much what it is, is a small air filter that connects to the end of your PCV hose. so instead of feeding it back into my intake manifold, it just releases the crankcase fumes back into the air. Just clean the back of the throttle body of all carbon build up and floor every now and then like j30t said.

[Talamascan]

Perhaps it is because you have a fairly new car with low milage, but if you only have a filter attached to the hose, I'm curious as to where the excess oil goes, because in my experience, there can be a significant amount of both gases and oil venting from the crankcases of most cars.

[J30tChumpCar]

I think that both of you have some good advice. The catch-can seems like a problematic "solution." I bought this car from the original, little old man owner, who probably never once floored it in 98,000 miles and, living on Oahu, I also rarely have an opportunity to floor it these days.

Based on this info you are definitely doing a disservice to the engine and yourself with your PCV delete proposal, heck I race a J30, it gets oil changes every 1300 miles and only deleted the system because it could not work properly in right hand turns under extreme G.
Between races I do see some moisture accumulate on the underside of the oil cap when driving short trips where the engine was not fully warmed, a side effect of no PCV, long term and with longer oil change intervals is where things go south.

[riaazfr1]

Perhaps it is because you have a fairly new car with low milage, but if you only have a filter attached to the hose, I'm curious as to where the excess oil goes, because in my experience, there can be a significant amount of both gases and oil venting from the crankcases of most cars.

Perhaps. But you do pose a good question about where the excess oil goes. Maybe it is hot enough that most of the oil is pretty much vapor????? idk for sure.

Here is what mine looks like:

Based on this info you are definitely doing a disservice to the engine and yourself with your PCV delete proposal, heck I race a J30, it gets oil changes every 1300 miles and only deleted the system because it could not work properly in right hand turns under extreme G.
Between races I do see some moisture accumulate on the underside of the oil cap when driving short trips where the engine was not fully warmed, a side effect of no PCV, long term and with longer oil change intervals is where things go south.

I understand that it will cause problems in the long run if there is no ventilation. But isn't there normally a small port in the engine block that the hose is connected to? so if you were to remove the hose altogether, it will still be ventilated unless that hole is blocked. is that right or am I misunderstanding your statement?

[J30tChumpCar]

There are only 4 ports all in the valve covers, 2 draw vapors out via the PCV valves and 2 allow fresh air in the block, removing the PCV eliminates the evacuation of moisture and such, the 2 inlet "vents" are in the intake bellows right at the throttle bodys where they get filtered metered air or in moments of excess crankase pressure they vent the overage to be burned rather then to atmosphere.

In my situation the 2 vents are left in place to deal with excess pressures generated in competition and the 2 PCV valves are welded closed and all plumbing removed/plugged

You are looking in the wrong place to solve this problem, its very likely you are simply a victim of putting around with what is essentially a hot rod engine from a 300z . Blow it out every once in a while and use Techron (by chevron) fuel additive every oil change.

[riaazfr1]

Ah, ok. That makes sense. Thanks!

[swimshark]

i am using the 300zx covers now so the intake vents under the plenum. i have lines that run to a catch can mounted in the bumper and now venting it to atmosphere via a small air filter with check valve.

[J30tChumpCar]

I looked at doing that last week but for my purposes there is no need to e pretty/tuck although there was evidence of some oil being ingested with my setup, everything is clean now so perhaps another couple races I can reevaluate the use of catch cans.