So I've decided to dig into my PCV system and basically add an air/oil separator between the 90* above the oil filter and the rear of the intake side valve cover. I've been told you can use the SR20 separator assembly but instead of trying to source one, I first would like to ask if anyone knows how they "work" so to speak. What is the internal design that separates the air from the oil?

I went through a couple different Nissan model cars and noticed a lot of them have a separator assembly in the crankcase ventilation system so why the left the CA18DET out is beyond me. I was thinking of building a baffled separator but want to make sure any design I would think to create would do what the SR20 separator is doing. Catch my drift?

Thanks for the help in advance.

Why not just do a crank scraper?

After reading a little bit about crank scraper's, I'm unsure if that would actually fix the problem of blow-by...I mean, I did notice the hose from that 90* bend above the oil filter did collapse so maybe that could have caused me some access crank pressure. After looking at the SR20, KA24, CA18DE (USDM), CA18ET, and other engines, most of the Nissan engines have a "breather separator assy" located on them.

What compression numbers do you show sjb? You should be able to drive the car HARD all day (at a drift/track day) with a catch can plumbed straight off the block fitting at the oil filter and not blow much oil at all.

Also, what turbo and how much boost?

I don't buy it when people say CA's are blowby machines. (I know i'm repeating myself here) When the intake and exhaust systems are designed properly they hardly puke at all in my experience. It definitely shouldn't be a "problem".

On the hose that connects the 90* above to oil filter to the pipe that reduces and goes to the back of the intake valve cover, that hose had collapsed. I wouldn't say I spray HUGE amounts of blow-by. I only empty my exhaust side can once every year or two and my intake side maybe once every two or three oil changes. I blew my dipstick a couple times at the drag strip last year (shifting at 8K MAX). I wouldn't say my PCV system is "hella dirty".

As for compression numbers, I haven't checked in awhile. last time I checked them was on a cold engine and I don't think I had the throttle body opened, also with an "Advance Auto Rent-a-Tool" Compression tester. I think it was like 100psi or so like this and it was within a couple PSI per cylinder.

Compression numbers seem pretty low.

How full is your intake side can when you empty it?

not very.