OK, the stock PCV system is 2 nipples on the oil fill neck. The one that points to the side goes to the PCV valve (grey/black plastic valve) that then connects to the large nipple on the front side of the upper intake manifold. The PCV opens at vacuum and closes under boost.

The nipple on the oil fill neck that points down goes to the metal hard lines on top of the engine and eventually goes to the primary turbo inlet duct. This is NOT a source of vacuum, it's a filtered atmospheric air source.

In 95 Mazda removed the PCV totally and just capped the side-facing nipple and the large nipple on the UIM.

When I do a catch can setup I run 2 hoses from the oil fill neck to 2 nipples on the catch can and the can has a breather filter up top. The PCV system will pressurize and has to vent, this lets it vent and any oily mess goes into the catch can and not into my intake tract to gum up the intercooler.

This is not a piston engine that needs the crankcase to be under vacuum or whatever. Rotaries just need the "crankcase" to be able to vent since it will build pressure as things heat up. The oil pan should be at atmospheric pressure.

Dale

 

So that being said, considering that I've got a single turbo setup, if I want to install the PCV valve, where should i connect that bottom nipple (on the oil filler neck)?

 

The only reason it goes to the turbo inlet duct stock is emissions reasons. Any potential emission source, and evaporative emissions is part of that, has to be burned by the engine and cleaned by the cat. The gas tank and oil pan can have fumes coming off and that has to be burned.

Since you are modified, you typically do a catch can. I think you said you have a Jaz catch can, that's what I have. Small catch can with a breather filter on top and 2 nipples. Run 2 hoses from the 2 oil fill neck ports to the can and you are done.

If you for some reason wanted to do it OEM-style you would have to have a nipple on the inlet to your turbo. Again, this is just atmospheric pressure, it will draw those fumes into the engine but it is not a hard vacuum.

Dale

 

It is clearly portrayed in the very diagram you posted. The bottom nipple should be routed to your intake. It doesn't have to be fancy just functional. If your problem disappears then you can focus on a clean install. I say this because you are just testing. Your problem indeed may persist even with the pvc installed. We're merely hunting down the culprit.

 

I think the OP is having a hard time with this since he is single turbo. He no longer has the nipple on the intake side to hook up the filler neck connection. Either way, since he has completed the tests outlined by Dale this has eliminated the PCV having any relation to his smoke issue.

If you are not confident about the pre mixed gas I would drain the tank and start fresh with a known properly mixed fuel.

 

He hasn't completed my test. My test cuts the PVC out of the picture. He did mention that the smoke seemingly lessened with cap open. It may not be enough, especially in a turbo setup.

You'd be surprised how much air those two lines will displace. And according to popular belief there is enough pressure that builds up in a rotary, that's why Mazda installed a PVC valve in the first place. His build might need vacuum assistance.

Now there's only one way to KNOW. To OP, the line can go anywhere. Pick a place on the UIM and you're done.

Again, to someone who knows what they're doing this should take 10 minutes, not days weeks or months.

 

If it was a 2nd gen you would have to route to the proper location but since the 3rd gen meters air differently you can literally plug it where you want(anywhere on the intake path).

 

Alright.

Oil catch can installed or not, PCV valve installed or not, it still smokes. And something seems to be so wrong with the timing. When I press the throttle, there's a small but noticeable delay before the RPM goes up.

 

That really isn't much smoke man. Not enough to worry about. I would agree with Dale that you simply need to drive the car. If it is your oil seals then just drive it til she blows and aim to do better next time. Just enjoy it the car. If your temps are good, you're not loosing coolant and you're not guzzling oil then drive it. You've spent so much time on the car, it's almost mid July and in Quebec you got 3 months of dry roads left lol.

Just GIVE 'ER!