Looking for some ideas on venting the oil system on an engine with removed emissions.
I have seen people use a nice oil catch can, or even drill a hole in the oil cap.
Lets see what you guys have done.

 

I recently posted this same topic. I have a S4 TII and I'll be running a catch can from my crank case vent and oil fill tube vent. I am hoping this will help cut down on some of the smoking issues I'm having with my project.

 

Leave the purge valve in place. Or install a generic PCV valve from the parts store.

Plumb the upper nipple on the oil filler through the purge/PCV valve to a vacuum port on the intake.

Connect the lower nipple on the middle iron to a line running to the catch can. If you have as standalone, just stick a filter on the catch can and be done with it. Stock ECU, you'll need to run the vent line for the catch can to after the AFM on the TID/intake tube.

Done and done.

 

Bone stock system. Just re-plumbed with silicon hoses. Never had any issues whatsoever. Unless you are running 10psi of boost or more i have found the stock system to work just fine. If you track the car regularly, get a baffled, oil pan.

 

great idea

 

I get that part. Makes sense, really. Manifold vacuum draws vapors out of the "crankcase."

Doesn't make sense.... I trust you've done the research, but I don't get why it'd work. If one nipple was open to manifold vacuum and the other is open to atmosphere (even through a filter) that's still a vacuum leak, right? Standalone or not... hell even taking the air from after the AFM will still be a vacuum leak. It's bypassing the throttle body, right?


Any explanation?

 

The lower nipple leads to a passage that ends down deep in the center iron by the eccentric shaft. In the stock setup, air is sucked into that passage, circulated around the crankcase, then drawn from the upper nipple. This is what should be done when rebuilding the system.

Air from after the AFM is not a vacuum leak because it is metered air. The stock setup draws air for the purge system from this location. All air is accounted for by the AFM and thus won't effect the fuel mixture.

Except Mazda complicates things a little by also tying the evap system into the PCV, which is annoying.

 

Right, I guess "vacuum leak" wouldn't be the correct term for it, but it's still air bypassing the throttle body, effectively doing what the idle adjust screw does on the S4 NA engine, or turning the screw on the BAC on a TII engine. It's all metered, but it's air getting around the butterflies that will raise the idle, right?

Good info here. I was wondering about that. I found this drawing a while ago and thought that it'd be kind of stupid if there was no passage or baffle to aid in drawing fresh air. Otherwise, it'd just be sucking air from the lower nipple straight through the filler neck to the intake, and that wouldn't do a damn thing for removing vapors.

 

Original message: AGreen, can you post a more visible jpeg? I'd like to see that catchcan set-up.

Nevermind. Searched "crankcase ventilation" and found it.

I've realized there's TONS of crankcase ventilation information.

 

here's what I did.

 

A tiny little flow of air may raise the idle a touch. But you can just turn it down if necessary. Also, remember that the stock purge valve opened under intake manifold vacuum and the stock system circulated air this way, so it's likely the idle adjustments have already compensated for it.

That's a good diagram. Most PCV valves are internally regulated to control the amount of air to just at trickle. They also often allow reverse flow, so that boost pressure can reverse the flow of air through the crankcase and blow contaminates out into the catch can/TID/filter/whatever. Personally I just have a check valve between the upper nipple and my manifold vacuum source, not a PCV. But my car is a bridgeport idling about 1400 RPM so a little extra air is of little consequence.

 

My setup is just like AmT-T.

Helps with the smoking!!

 

I used to have mine routed the wat Aaron Cake suggests, but I found that it actually made my car smoke. No doubt my pcv valve was shot or something. So I just capped the hole that leads into the intake to prevent a vac leak and let the line that used to go there just hang. I now have no smoke, and I had a solid Idle. Also no oil ever came out of that line so I never put in a catch can.

I changed my vac line setup when I did this btw. Now the vent from the center iron and the oil neck t together and just lead over toward the intake and vent to atmosphere. still no oil comes out and my car doesnt smoke... super simple