V1 PCV For Boosted N/A Engines

[jirwin]

Hey guys, I've finally gotten around to turboing my little 2.2L and I need help figuring out a PCV system for it. When it was supercharged I vented everything to atmosphere, but with the TVS that started to become a problem when I got into higher boost. It was pushing oil out seals from too high of crank case pressure.

So... I'm switching back to a full PCV system and I need help designing it.

I believe this is the stock 2.2L (or any Ecotec NA) setup:

This is how I have mine currently. The LSJ intake manifold does not line up with the PCV hole in the head of the 2.2L LAP, so its effectively blocked.

This seems to work ok, but I'm not sure how well it works under cruising conditions. I was thinking about adding another line and a check valve like so:

I'm thinking that this would work, but I'm not 100% sure since technically its bypassing the throttle body. It is metered air since its post-MAF (I think that's how that works). The idea would be that under cruise/idle conditions the intake manifold connection would have higher vacuum and pull air thru the check valve and thru the breather. It might bypass the turbo and charge pipe but that shouldn't matter because its still metered air post-MAF. Then, under boost the intake manifold would pressurize and the check valve would close. The crankcase would begin to pressurize and the existing route from the breather to the turbo inlet would pull any pressurized crank case gases out, and back into the turbo, intake, and eventually engine. Does this make sense? I think it would work.

P.S. In my diagrams I have left out the catch can for simplicity.

P.P.S. If anyone knows how the PCV system works on the stock LNF I would love to see a diagram.

 

[Rauq]

Ooh boy, I love this stuff.

Let me start off by saying, I haven't tried looking it up again, but I believe I'd read somewhere once upon a time that ZZP's phenolic intake manifold spacer could be used to connect an LSJ intake manifold PCV valve to the PCV port on a non-LSJ head. If this seems viable to you, well there's your solution.

Regarding your proposal in the last graphic, you'd need a check valve between the breather and intake tube to ensure you're not just pulling air from the intake tube into the intake, bypassing the throttle body.

The thing you're missing, I think, is pulling fresh air into and through the crankcase. In a stock LSJ, with manifold vacuum, fresh air is pulled in through the valve cover breather, through the crankcase, and into the intake manifold. With the PCV valve closed (boost), there is no fresh air circulation through the crankcase. Without an intake manifold PCV valve or any other secondary crankcase ventilation port, you can't get circulation through the crankcase. I don't know how undesirable this is. I also don't know how much more crankcase fumes you're going to get out of the motor by pulling on it with intake vacuum versus intake tube airflow, but in any case, you should be doing a decent job of preempting crankcase pressurization.

If you can't get the manifold PCV valve to do anything, I'd think the best you could do is piping the valve cover breather to the intake pre-turbo, and that'd probably be fine.

I'll add too, my LSJ never seemed to care too much about pulling unmetered air through the PCV valve.

edit: to be clear I have no LNF PCV experience, but from my limited understanding of what I've read, there is an additional valve cover port that pipes directly down into the crankcase. I don't think that or any other significant difference in configuration has any relevance to your setup.

 

[jirwin]

Haha I'm glad you chimed in since you have one of the more complicated setups being twincharged

Let me start off by saying, I haven't tried looking it up again, but I believe I'd read somewhere once upon a time that ZZP's phenolic intake manifold spacer could be used to connect an LSJ intake manifold PCV valve to the PCV port on a non-LSJ head. If this seems viable to you, well there's your solution.

Yes I saw this too and I'm considering it since I do have the phenolic spacer. Without the supercharger its a bit less of a headache to take off the intake manifold.

Regarding your proposal in the last graphic, you'd need a check valve between the breather and intake tube to ensure you're not just pulling air from the intake tube into the intake, bypassing the throttle body.

So let me think this through. If I'm cruise/idle then the intake manifold check valve would be open and pulling air. Then another check valve would be on the turbo inlet one, only allowing air to flow TO the turbo, not FROM it. This would flip under boost. Makes sense I guess.

The thing you're missing, I think, is pulling fresh air into and through the crankcase. In a stock LSJ, with manifold vacuum, fresh air is pulled in through the valve cover breather, through the crankcase, and into the intake manifold. With the PCV valve closed (boost), there is no fresh air circulation through the crankcase. Without an intake manifold PCV valve or any other secondary crankcase ventilation port, you can't get circulation through the crankcase. I don't know how undesirable this is. I also don't know how much more crankcase fumes you're going to get out of the motor by pulling on it with intake vacuum versus intake tube airflow, but in any case, you should be doing a decent job of preempting crankcase pressurization.

I guess I didn't realize that it was flowing thru the crankcase in that manner.

 

[Rauq]

So let me think this through. If I'm cruise/idle then the intake manifold check valve would be open and pulling air. Then another check valve would be on the turbo inlet one, only allowing air to flow TO the turbo, not FROM it. This would flip under boost. Makes sense I guess.

If you can get the intake manifold check valve to work, then all you need is to pipe the valve cover breather to the intake tube*

If you can't, and you want to pipe the valve cover port to the intake tube AND the intake manifold, then you would need a check valve between the intake manifold and valve cover to ensure you're not blowing boost into the crankcase, and between the valve cover and intake tube to ensure you're not just sucking past the throttle body.

But yeah, flowing through the crankcase was the hardest thing for me to wrap my mind around at first. Also makes fitting a catch can a little wonky because depending on state the flow through the line between the valve cover and intake tube reverses.

*I just ran a breather filter on the valve cover port for a long time, so it was pulling unmetered but filtered air through the crankcase in vacuum, and allowing boost crankcase pressure to vent out otherwise. Never seemed to bother the tune and stayed pretty clean, never had any oil dipstick problems either.

 

[jirwin]

Thinking about it more the problem with my original solutionis the size of the line really. An 8AN "PCV" bypassing the throttle body flows a TON more than the stock PCV I imagine

 

[Dsteinhorst]

Josh, sorry I haven't replied to your message. I was trying to find pictures of the hole I drilled, but I'll look later. Essentially, I drilled an 1/8" hole in the aluminum of the head right in the middle of where the LSJ gasket PCV hole is. The LAP head still has a void inside and allows crankcase gasses to flow through.

This setup works exactly like the LSJ PCV.

 

[jirwin]

Thanks @Dsteinhorst, appreciate it. Thoughts on doing that with the head still on the engine? Metal shavings?

 

[Dsteinhorst]

I did it head on. There's 110k on my stock motor, so I don't have as much invested as your built motor. There is a passage where you can see the area. There were a couple shavings I pulled out with a dab of grease on the tip of a screwdriver.

I saw somewhere, maybe FB group you can also just cut out the LSJ gasket between where the LAP hole is and the LSJ hole is and that will flow enough. That's likely the easiest as well.

 

[jirwin]

The latter is what I think I'm going to try first. Thanks for your help, appreciate it

 

[Dsteinhorst]

Yeah when I saw that post, my response was, "I wish someone told me that before I got the drill out!"

 

[jirwin]

We'll see how well this works

 

[Dsteinhorst]

That's going to be perfect.

After I did mine, I noticed the throttle is a bit touchier. I dialed way back light throttle response in HPTuners to combat it.