Actually, the more I think about it, the two valves have to be the same. With no vacuum, they are closed because of a spring inside pushing them to a closed position. With some vacuum, the flow is metered.

So with the hose in the filter end, there is probably no vacuum at idle, and I'd expect no vacuum at any condition since the filter is free flowing. With no vacuum the valve is closed unless for some reason there is enough crankcase pressure to push the valve open. The difference between this setup and the stock setup is that the valves act more as simple check valves with the ATI configuration.

 

Garyk, I agree with you that the use of two PCV valves does even it out more. The thing that really got me thinking about it mainly was the fact that my idle is horrible and if the PCV was seeing NO vacuum at the end of that air filter (uh oh, I'm using it again ) and not venting any crankcase pressure it could've been a cause of my symptoms. I had a similar symptom in an old VW where the guy I bought the engine from did not put any kind of oil breather on the engine, it idled like crap. Since I'm apparently the only one seeing this problem I do need to go check for vacuum leaks.

 

Jesse, just saw your post with the diagrams. Our pcv valves should work like those diagrams suggest, which is to say they are a modified check valve. They serve another function in metering flow based on vacuum. With the ATI, they essentially turn into plain old check valves, as SVTkid alluded to. One thing I don't agree with though is the valve position at idle. On stock system, the valve is open but metered for low flow. On ATI system, the valve is completely closed (its not exposed to the vacuum in the intake plenum).

BTW, how bad is your idle? I think mine might hunt a little bit now, but not much. Don't know if it ever did it before...

 

Garyk, regarding your post before last. That's exactly my point. How do we know that the crankcase pressures can overcome the spring tension to vent the gasses? The fact is... we don't especially at idle. If no gasses are being vented then we run the risk of leaving contaminants in the engine. Maybe it works fine though, I'm just trying to stir up a theoretical discussion with a problem. I'd like to avoid all problems if possible. Personally, I'm thinking of relocating the PCV line to the metal elbow after the air filter. Just to see what happens.

 

My idle is not terrible, but I had an almost perfect idle before. NOW, maybe every 10-15 seconds it will drop for a little bit then go back to normal. I was thinking that was over pressurization finally overcoming PCV spring tension.

 

Another thing that happens to me is that as if I'm driving like normal and then I let completely off of the accelerator pedal, the idle drops even lower 400-500 RPM and then the engine compensates. The first couple times it happened, I thought the engine was going to stall, but now I'm kinda used to it.

 

Wow... this is really getting to be a lot of reading!!!

Anyway Jesse... I want to bring up one more point before I pretty much step ot of this conversation. You say there isn't any vacuum on the ATI set up. I beg to differ on this one. Since the compressort is actually a fan, doesn't it stand to reason that pulling air through a tube is indeed a vacuum? The compressor turns a vacuum into positive pressure. Am I wrong?

And check valves aren't entirely old school yet. The LS1's (Vettes, Camaros) still use the check valve style set up. You can rattle it around and here it flopping back and forth. No point really here, just a bit of info.

Thanks for the good info and reading. I still am learning a lot about the 350's.

 

The Spring rate on the passanger side valve cover is very very very weak. So a very small amount of crank case pressure would be able to blow it open, even if not connected onto the intake of a blower or turbo.

On the installation of the end of the filter. I have placed them on the rubber connector that goes between the metal 45 and the plastic intake. It looks cleaner in my opinion, and would also add more longevity to the ait filter, since no oil mist would be getting into the filter. Well maybe some would still due to reverberation, but that would be minimal. You could also drill a hole in the metal or plastic if you wanted, but thats more work then poking a small hole.

The spring in the PCV valve is not really for metering. It is so that as soon as o" of vacuum is achived, there is a little extra help sealing it shut. Some PCV valves you literaly a "ball" some use a spring and plunger. The Z/G35 use the spring stile. The drivers side valve cover doesn't even have a valve in it at all. Just a big tube that is attached to the backside of the valve cover. So there would be no metering ability at all with that.

Like I said before, I am not saying any of this to be mean. But I don't want anyone to every be scared of forced induction of anyform. And lastly not because of a PCV concern, that is so simple.

EA

 

EA, I agree that nobody should be concerned or scared of forced induction because of the pcv system. I really don't think there is a problem, I'm just in here because I'd like to know exactly how it works. I figured there must be something different with the driver's side because of where it hooks up normally. If that is true that it has no valve in the drivers side, then it doesn't matter too much what the other side is doing. I was going to recommend running without a valve anyway if anyone is really worried about crankcase vapors. If I get some spare time, I might check my system out to double check you on that drivers side though

 

Garyk, Sounds like a plan. The "stock" system uses that drivers side as a vent intake. So that if for some strange reason the motor needed air in the crank case. (this would be odd) then there would be a place for the motor to take a deep breath so to speak.

There are three reasons why this is connected to the intake air, and not just open to the air.

1. Emissions, the good old gov. likes things to be nice and contained.
2. Smell, when it's discharging a burn oil smell is present. (like when you pull the oil cap off when running)
3. Filtered air, incase it needs to suck in air, it would be filtered air.

EA

 

Well, I hope this thread hasn't scared anyone away from forced induction. I don't want to say 7psi is harmless, but pretty damn close to it. I appreciate your guys input on this. I never actually saw the location of the other valve, I just assumed it would be similar to the passenger side. I feel much better now.

 

Just an update on my crappy idle:

I pulled the vacuum tee off of the plenum connection where the stock PCV hose would go. I blew into it to see if I had a vacuum leak and I had a bad one. Put some loctite on the threads and tightened it back up and now it idles near perfect.

 

I recently had engine oil gushing out of the crankcase gasket and oil filler cover gasket?

Anyone, had a similar experience?

Thanks
G

 

yes "had' being the key word fotunetely. Leak Down/Compression test time! GL!

LOL,

So now we have come full circle, cue the ELTON JOHN Music for Circle of Life because I have a secret too Neener



My car is dialed and it was done without help from the Installer, Vendor or Manafacturer and although costly, it feels d@mn good.

 

Explain gushing.

Here's me hoping that it's just a loose valve cover. Some of the valve cover bolts came loose from the factory. I don't know of anyone who had it coming from the valve cover gasket and oil filler gasket.

 

The oil was leaking out from the valve cover gasket area, and I lost 2 pints over.

I drove 20 miles, boosting obviously, and when I arrived at my destination puffs of bluish smoke appeared from both sides of the engine. When I look beneath the engine, I noted that the oil was all over and dripping.

The oil filler cover was still screwed on and the car was drivable. Took it back to Nissan workshop and some kind of dye was used and with blacklight and special glasses, the Nissan technician traced the source of the leaks.

The Nissan technician did speak to ATI tech support in correcting the problem.

The valve cover and filler cap gasket were replaced and the problem did not resurface.

The engine was fine when I dynoed and tuned the car later that week, with a group of over 35 drivers at XXTuning. The car did have multi cylinder misfire until the sparks plugs were renewed.

G

 

Whew, that's good it was just loose valve covers. Those are especially important for boosted Z's because of the increased crankcase pressures. The way you posted, I thought this was a new problem.

 

You can imagine the pictures flashing through my mind when I saw the smoke balloning from each side of the engine compartment......Oh Shoot

It was a close call, could have been worst; in addition to the possibilities of a loose valve cover; the rerouting of the blow out valve was also suspect. However, ATI insisted that they never had a problem with the PVC valve. It could also have been a pinched line or the bypass valve, which could have diminished the necessary vacuum required to vent the crankcase positive pressure; plus the blow-by gasses are at a maximum under heavy load.…….ka-boom the weakest link fails…in my case the crankcase seal.

I consider myself pretty, pretty fortunate that the valve cover wasn’t seated properly; or else something more critical could have gone, not just ka-boom…….but ka-put

If I could improve on the PCV and Bypass valve....I would

Thanks

G

 

In most cases blowing oil from the oil fill cap or the valve cover seals is a sure sign of PCV restriction issues.

My personal opinion.

G