Yeap. As he said, good news is by blocking PCV the only thing coming out of the breather is whatever leaks past the rings. My motor in the car right now currently does NOT have broken ring lands and has fresh rings, so basically nothing comes out of the breather. On my last motor when I broke a ring land at 31 PSI, there was a ton of blowby pouring out of the breather at IDLE. Rev it and it was comical.

I don't know if PCV is actually better for your oil or not (maybe?) but it definitely lets 10,000 more oil into the engine than the breather does. Even if you put a catch can on the PCV side still some is going to go in the engine, and then you have a catch can to drain/clean. I've run without PCV for 8 years so far and have not had a problem that I know of, never had blowby problems, I run all the boost.

If your oil strongly smells like fuel I'm guessing you have a mechanical problem.

You have the two lines on your valve cover going to one catch can with a breather, am I right? Look at that setup, look at it long and hard. How it it ever supposed to do anything, air does not move on it's own.

Any time you are not in boost, the PCV is sucking air out of your block and into the intake manifold. It gets this air through a breather on the exhaust side. We don't like this garbage being burned, so we install a catch can between the PCV valve and intake manifold. We don't use fine steel wool, because that's dumb and kills the airflow that actually rids our oil of fuel.

I can't explain any better than this. Auto manufacturers have known since the beginning of time that even brand new rings leak and that ridding the block or even pulling a slight vacuum to help them seal is a good idea. The only reason PCV exists is because the epa won't let them dump straight to the air with drag vac tubes any more, and they don't care enough to buy a catch can when they can turn the timing down.

So why is it when I was running a breather on the exhaust side and then a can between the passanger's side of the cover to the intake manifold I was FILLING it with oil within 100 miles? Was I missing a PCV somewhere?

Because your motor is probably junk, you have an unmodified valve cover or plenty of other reasons...

Motor is at 2000 miles on the build and runs good. Should I check leakdown?

What do I need to modify about the valve cover? It's confusing because on page 2 of this people said that the setup I had was fine.

In case this isn't clear to anyone reading this, PCV is an emissions device, and it's not pulling a vacuum on the block/improving ring sealing. The amount of airflow going through a PCV valve is very very small, like REALLY small. You could install 10 of them and I bet you still couldn't measure more than a few kPa of vacuum.

Sure why not? Rule that out would be nice.

I have not modified my 99' or 01 valve covers, and never had problems but again, I don't run PCV.

My setup:

Block PCV valve/don't use it.

Pipe breather tube upstream of turbo/sc/air filter. Install catch can here if you wish, but not required in my experience.

Done.

So if I was to run a can between the intake manifold and the intake side of the valve cover, would I use a PCV or drill it out and make it just a tube?

this is another setup I had. Why did this fill with oil so fast? Was it because we were pulling from the wrong side of the cover?

https://www.miataturbo.net/attachmen...ine=1428527446

This is the difference I am seeing so far. Everyone else has it between the intake side of the motor and the intake manifold, not the exhaust and intake manifold.

The one thing I thought was happening is that the pressure in the manifold was actually causing enough suction to just suck air out of the valve cover and into the can. That's why I disconnected the can from the intake manifold completely. I didn't know the different sides of the cover had different functions.

If you turn right hard, like with slicks, you gonna pool oil right where the pcv picks up and suck a whole bunch out. I blocked mine with a cutoff wheel stud shoved into the rubber grommet. My air/oil separator does what its name implies and I dont get any oil into my intake unless I fill the drain up and siphon it out of the separator. I dont mean "like no oil" I mean, you touch the inside of the intake tube and the inside of the turbo and your finger doesnt come back greasy feeling. And no you cant buy my a/o separator, too much of a pain in the ass to make the first one to make it worth making a 2nd.

If you have gas smelling oil you've either got toasted rings or you're running way too rich.

I'm not much of a detective...but I might have found your problem

I doubt i have toasted rings since they were filed about 2000 miles ago for a freshly honed bore.

Rich is a concern. I do want to get my can setup in order as well. As I said, I get black clouds if I do a hard pull to redline, and I am using SOME oil, but as my tuner said, a high power turbo car will use oil. I am not adding enough to be concerned about it, had to add .5qt after my tuner had it for 3 weeks but since then its been pretty solid level (till we just changed it). Rich I mean I am running 11.5:1 at WOT.

I am not shitting any bricks until Blackstone tells me to but when my mechanic said that it would lead to much quicker bearing wear, I pooped a little.

Running 17psi from an EFR and making 311whp is more than the tiny volume of the crankcase, the chambers of the valve cover, and the little lines going to your little catch can can handle. You are at roughly three times the stock power with the same size expansion volume in your crankcase and wee tiny openings to let it out. The velocity of the gasses trying to get through those little ports is going to be in excess of the design parameters of the system.
It would be advantageous to do any or all of the following:
1. increase crankcase volume
2. increase the opening sizes that the vapors pass through in the valve cover
3. increase the diameter of the evacuation lines
4. increase the volume of the catch can

The #1 above would decrease the pressure rise with each pulse by allowing a larger expansion volume. The #2 above would allow the gasses to travel more slowly and allow the oil to settle out of the gasses better. #3 is the same as #2 in that slower moving gasses aren't going to carry as much liquid to the catch can. #4 allows the vapor to slow and the liquids to fall out of suspension. If the can has too small a volume then the filter will puke oil regularly. A large set of lines hooked to large passages and a large can will emulate a larger crankcase volume as well.

If you can see black smoke in your rear view mirror under acceleration and you aren't running diesel, you have a shitty tune and a shitty tuner.

Running excessively rich will wash down the cylinders and cause excess ring wear which means more blowby. 2000 miles of shit tune is more than enough to junk a set of rings and necessitate a rehone/rering.

Thank you for the very detailed and helpful answer, among some of the more smart-ass replies this really is great! I've barely driven the car in 7 months and have not worked on it in almost a year and have had other priorities so I kind of forgot how everything works. Looks like I need to do some valve cover modding. Will search more.

Thanks again Sixshooter!
The tuner I use is actually quite liked and experienced tuning Miatas. We do have some adjustments to do however. 2000 miles on the motor but I have not really been beating on it, just open it up time to time (I've learned to respect the power) so hopefully everything is still good.

Something is messed up if you can see the black smoke yourself and your wideband says 11.5:1. Probably the wideband not reading accurately for <insert long list of reasons here that cause widebands to read lean>.

Agreed. I had this problem way back, by the time I "fixed" the tune it was slower and black smoking. Then a few weeks later the sensor died completely. New sensor, and aww shucks it was pig rich. Retuned back to 11:1 AFR and no more smoke. But as you say could very well be a leak in the exhaust system.

Hell the motor in my car now I ran in the high 9's (racing with bad intercooler setup, 170F* AITs) and no cat and it didn't smoke! But it's 10.5:1 comp and was a new motor. My lower comp motors of the past smoked at that AFR. Both were obviously down on power/too rich/not good for motor but too rich is better than detonation for that night of drag racing. Now maybe soviet can tell me 9:1 is rich again.

I will work on the rich issues with my tuner, it is quite possible that my WBo2 sensor is out of wack, its pretty old.

However, on the catch-can, does it make sense that the can would be collecting oil at a rapid rate because I had the hose hooked to the wrong side of the valve cover, or should it not be collecting oil that fast no matter which side of the valve cover I am connected to? I do not understand how the baffles there work but I do remember that the OEM configuration is from the intake side of the engine right to the manifold (with pcv), and then the stock catch-can was connected to the exhaust side of the valve cover and then eventually went back to the pre-turbo intake and had a return line to the oil pan for overflow. The setup I had that collected excess oil was a can between the exhaust side of the cover and to the intake manifold

I will try to change the setup and run the can between the intake and intake manifold, vs the exhaust side and intake manifold like before, and see if anything changes. Does it matter if I have a PCV in the intake side of the valve cover?

Yes use PCV valve, yes install PCV system on intake side. That may be why you're having problems.

On a street car I would certainly want a pcv valve on the passengers side and maybe have a catch can on it. The main purpose of the PCV valve is to regulate the amount of vacuum being pulled on the crank case so that you dont pull the full 20inHG ish manifold vacuum that you do in overrun, or even pull the full vacuum of idle. On a racecar with slicks I'd pass on it.

So if I understand correctly. Leave the PCV in it's spot, run a hose from it to a catch-can, then run the return hose to the barb on the intake manifold, and done?

Seems simple, and what we had before, except pulling from the wrong cover side.