Guys,

What does the line that goes directly downwards from the oil filler neck do?

IIRC it connects to a meal pipe that runs across the top of the engine, and then goes into the primary turbo intake elbow right by the turbo. Am i right?

The reason i ask is because im installing an oil catch tank and i want to block it off. That should be ok right, providing i have a catch tank?

Thanks

Bob

 

Yes, you are correct as to where it goes. You'll need to have it vented somewhere. The line on the primary intake elbow is a vacuum source. Some people have just blocked it off, run the line to a catch tank and then vented the catch tank. IMO, I would keep the line venting to the primary intake elbow and then put your catch tank inline before it goes to to the intake elbow.

 

Why will i need to have it vented to somewhere?

I thought the line just went from primary intake elbow (before turbo) and straight into the oil filler neck, allowing intake of gases from the sump?

Surely if i just block this off at both ends and run the second line from the oil filler neck (the one that normally goes through the PCV valve and into the intake) to the catch tank and vent the catch tank either back into the UIM where the line used to plug to, or block the UIM port and vent the catch tank to atmosphere this will be ok?

sorry dont mean to ask a question then tell you your answers wrong ( i hate it when people do that!) but the answer youve provided denys the logic of my question?

 

The reason I would still vent it to the primary intake elbow is that is a constant vacuum source (i.e. it constantly pulling the gases/fumes). The line to the UIM only draws the fumes when the manifold is at vacuum which is why the check valve is there (to not pressurize the oil system on where the UIM sees boost).

Like I said, you could just vent the catch can, but that will release the fumes/gas just out into the open. Some tracks here in the USA don't like that. Releasing it back into the intake will just send it through the intake and out the exhaust so you don't incur any additional odors coming from the car. That oil can smell like gas after a little while as you'll note when changing the oil. Imagine that smell being vented out under your hood just into the open.

 

ahh i see what you mean, the vacuum created from the inlet keeps sucking the fumes out of the sump and back into the intake when your on the throttle, and the other line with the PCV sucks them out when your off the throttle.

Ill come up with something, thanks very much for the help dude!

 

Apparently Mazda removed the PCV line in 95. Here's some info on it and catch tanks:

http://www.robrobinette.com/pcv.htm

 

Yes, they removed the passage to the UIM, but kept the one to the intake elbow. I never really saw the point in that one if you already have the constant vacuum source from the primary intake as it would be doing most of the work.

 

Yeah I wondered about that too.

 

Another reason to place the catch-tank in-line with the line running to the primary intake elbow, instead of just plugging it - if your catch-tank fills up with oil, the excess will get sucked into the intake and end up in the bottom of your intercooler instead of all over your car or the track. While its a drag to have to clean out the intercooler, it beats the alternative.