I have a 2008 350z with admin tuning intakes that do not have the PCV port. I’m looking to run a dual catch can setup but I’m trying to figure out the best setup to run and so far, I’ve been getting mixed answers. Should I run two VTA cans on both sides or should I run one VTA can on the intake/inlet side and one closed/“vent to engine” catch can on the vacuum/pcv side?

Thanks!

 

The more I've read up on PCV systems and their purpose/function, the more I realize that VTA systems are not such a good idea for a daily driver.

Since there's no active vacuum pulled with a pure VTA setup, unburnt fuel vapors and blow-by gases will start to build up in your crankcase and mix with the oil. This can lead to sludge, especially if you don't adhere to frequent oil changes. Venting to atmo ensures you don't have positive pressure buildup in the crankcase causing blown oil seals and other bad things to happen, but it doesn't give the benefits of a vacuum to assist with removing those contaminants.

That being said, in your situation I would go with a mini crankcase filter on the inlet side cylinder bank (where the factory PCV hose would connect to the intake tube before the throttle body) and closed catch can on the vacuum PCV side (where the factory PCV hose would connect to the intake plenum after the throttle body). Not as ideal as a fully closed loop system, but the next best thing.
Cheers!
-Icer

 

Can confirm Icer's advice as that's the setup I'm running on my HR. I have a small crankcase filter on the driver's side outlet where it used to connect to the factory intake hose, and a non-vented catch can connected to the PCV valve. The catch can outlet is connected to the stock port on the back of my intake manifold. Full disclosure, I'm not sure if this is even the optimal setup since this is my first oil catch can, but it seems to be working okay for my boosted Z. Excuse the filthy engine bay, but here's a quick mock-up.

 

Already gave my 2 cents, the breather on the port is not a good idea because it leads to oil misting everywhere.

 

that is a boost leak waiting to happen, and it's not a good way to route it.

 

Yea it’s just annoying since I’ve been getting VARIOUS different answers from people that are very experienced with this platform. I’ve heard people tell me two VTA cans are the best since one closed can on the breather port will cause a vacuum leak (I’ve heard this from like 2-3 people).

So right now, I have no clue what setup to go for with the different answer I’m getting lol, that’s why I came here

 

Ok, but out of all the people giving you opinions, how many of them besides me fit this criteria:
1. Owned the platform for 17+ years
2. ASE certified master mechanic
Not only do I know how this stuff works from school, I have experience AND knowledge on my side.

Also, I did tell you that a fully closed system is better regardless, there is always a compromise.
What would I do? Have nipples welded onto the pipes and run it like Nissan designed it, but I am VERY **** with stuff like that, I rather not change the way something is designed, unless I know 100% it's for the better.

 

Got it, but why would people say running the one VTA can on the vent side and one closed can on the vacuum side cause a vacuum leak? I’ve asked the guy at RS-Enthalpy and RZG Motorsports and they said the same thing about running two VTA cans so there’s no pull back/leak between them. These are also guys very experienced with the platform

 

What exactly is the boost leak waiting for? I also don't have any "oil misting everywhere" from my breather. How would you recommend routing the catch can(s)?

 

No offense to those guys, I wouldn't let them touch my car.
every tuner on the planet is going to tell you to VTA, that doesn't make it the right answer, I'm sorry.
Look at the diagram I'm going to put up and think about it logically, tell me where the vacuum leak is going to come from? As an exercise, imagine the the intake tubes are the blue catch can and the filters are the breather. It's THE same thing minus the occasional vacuum assist.

 

If you look at how the boosted guy has it, its basically a short version without a can, same premise.

 

ok, so if this is the way you have it, every time you hit boost, EVERYTHING outlined in yellow is getting pressurized with whatever psi you are running. This is also, forcing the PCV valve closed when it shouldn't be.

Also, not every car will mist, it depends on driving behavior and engine condition.

 

Increase size, eliminate PVC valve and aspirate both side using the turbo, if you look at most OG FI kits they will have a port in the intake before the turbo/blower that will go to the head on the vent side.

 

Since there's no active vacuum pulled with a pure VTA setup, unburnt fuel vapors and blow-by gases will start to build up in your crankcase and mix with the oil. This can lead to sludge, especially if you don't adhere to frequent oil changes. Venting to atmo ensures you don't have positive pressure buildup in the crankcase causing blown oil seals and other bad things to happen, but it doesn't give the benefits of a vacuum to assist with removing those contaminants.