Crankcase ventilation?

[MidnightOwl]

Okay, I have an 87 TII engine in my vert. I have the emissions removed, so the charcoal canister is gone. I've been doing a little research into crankcase ventilation, and needed a little bit of clarification.

I read that improper ventilation could lead to oil problems, such as blow-by in the turbo, and other phenomena. On my engine, on the intermediate iron, there is a nipple below the oil filler neck, which is capped. The nipple on the oil filler neck is open.

From what I understand, the nipples are used for crankcase ventilation. Air is sucked in from the lower nipple, through the engine, and the upper nipple is used to vent the gases/whatever. Now, from what I understand, the oil catch can is what you use to collect the vapors and oil residue if you have removed the stock systems.

The set ups that I have seen have a breather on the lower nipple, and the catch can attached to the upper nipple. I've also seen a breather on the lower nipple, and the upper nipple attached to a PCV valve which is connected to the intake manifold. I've also seen the lower and upper nipples connected to a vented catch can!

My question is, what can I do? From what I've gathered, I should be able to just attach a breather to the lower nipple to allow airflow in, then attach some sort of canister to the upper nipple to collect the misc stuff coming out.

[djmtsu]

I have the lower nipple capped and the upper is just left open. I have NEVER found any oil spray in the engine bay. I know alot of guys running this way.

[Ender]

I have the lower capped and the upper connected to a breather filter, BUT I didn't do a ton of research before doing it. I haven't, however, noticed ANY problems whatsoever, and that includes doing an oil change, redlining and boosting frequently, and an autocross meet.

[Smoken']

In order to keep dirt and stuff out there needs to be a filter of some type. Capping the lower will be fine, but i would run the upper nipple to a catch can or something. That way it can vent, but still keep dirt and grime out.

[MidnightOwl]

Cool, I've been real paranoid about it for some reason. I just want to double check. I'm still gonna put a catch can on the top nipple, but I guess leaving the bottom capped is what I'll do. Thanks.

[Ender]

I figured that a filter should catch stuff just as well. Is there really that much one way airflow through the crankcase?

[classicauto]

I have my crank vent (lower nipple) ran into a catch can directly (no PCV) and use a nipple on my filler cap to feed the other inlet on the catch can. You *could* use the existing nipple but i still have a charcoal canister.

I get about 1/8 pint of moisture (1 pint can) every 1000kms of street driving. Hard driving should produce a little more.

[FerociousP]

i have both mine open, and i'm getting a little moisture in my system, i may try a catch can and see if it makes a difference..

[MidnightOwl]

Originally Posted by classicauto

I have my crank vent (lower nipple) ran into a catch can directly (no PCV) and use a nipple on my filler cap to feed the other inlet on the catch can. You *could* use the existing nipple but i still have a charcoal canister.

I get about 1/8 pint of moisture (1 pint can) every 1000kms of street driving. Hard driving should produce a little more.

That's the set up I saw on some FDs over on the other forum. Do you need a vacuum source on the catch can, or does it have it's own ventilation or what?

[classicauto]

Sorry should've mentioned.

Its a vented catch can, I'm not using any vaccum on it.

[FC3S Murray]

This is what I have on my 2 nipple E-bay catch can. (picture)

Filter is the type from checker/schucks that is spectre brand.

No pcv valve.


I hope this is approved, I collect only about MAYBE 2 TBSP's of moisture after a cruise. I simply just lower the long hose from the lower nipple to let the collected fluid in the hose bend drian to the catch can after shut down(hose sags a little from lower nipple to the plastic "T").

**My only concern is if we get a huge amount of oil "crank blow by" in the oil filler tube it WILL never get out that upper nipple due to the incline of the filler tube.....it will just run back down into the motor. Crank case "sludge" is horrible for oil, internals and seals in piston motors and I am sure it is the same for our motors. Am I thinking right???

[RETed]

You really only need one.
You're not flowing gobs of liquid through the fittings / hoses, and you're technically only venting vapors from the "crankcase".
Mazda complicates everything due to emissions. :P

If you're going to TRACK the car, cap the lower fitting!
Oil can climb up the passage and actually dump out of the lower fitting.
This is a good reason to always use the top fitting as a rule of thumb.


-Ted

[FC3S Murray]

thanks Ted.

[88turboii]

and a lot of air does move out of the crankcase. i had mine incorrectly vented and it built up enough pressure to pop teh oil filler tube off. i now have the upper capped and the lower going to a port on the TID with no problems

[MazdaMike]

Its not air, its Positive Pressure in the crankcase. If not properly vented can easily pop out seals like your front main or rear main, or just make every seal leak.
Though most of you may already know the point of the PCV system is to vent that pressure and recirculate it for combustion, not only do oil vapours contribute to airborne HC emissions, I believe they also form a particulate in the air which is also harmful to humans. For the life of me I can't remember why theres positive pressure, all I can remember is the vapors and mist are from the oil sloshing around the crankcase.