catch can in place of ccv?

[haaken675]

Hey guys, trying to figure this one out but haven't been able to confirm my thoughts yet. I am swapping an m52b28 into my car and throwing a turbo on it while I'm at it. I obviously do not want positive crank case pressure, and from what I can tell, I would be creating just that. My thought was to vent from the valve cover into a catch can with either a vent to atmosphere (with filter of course), vent to atmosphere with the other line going into the dipstick tube (not sure if this would help or hurt), or vent from the valve cover into a catch can with a good quality one way valve into the intake like the old ccv would to help create some negative pressure in the crank case until boost comes on.

Thoughts on what would make the most sense? Not worried about throwing codes as a) I have to tune for the turbo anyways, and b) I think I am going to go with he new MSpnp Pro coming out for the m50/52 motors so I can tune it however I like anyways/

[haaken675]

Did some thinking. Would a setup were I ran a catch can from the valve cover vent into a baffled catch can and then to a line running to the turbo intake work in my benefit? I am inclined to think yes, but I wasn't sure if this would in turn create too much vacuum...

Also, anyone know where the clean air intake is in regards to crankcase ventilation? Can't find it on diagrams.

[Northern]

Three ways to pull vacuum on a turbo setup:

1. Compressor inlet.
Pros: Easiest solution that pulls vacuum. Poke a hole, run a hose, plug the manifold(or M50).
Cons: Oil in intake seems unavoidable even with E36 CCV/E39 CCV/Catch can inline. Would mostly worry about fouling a MAF if you have one.

2. Exhaust scavenger.
Pros: Fairly cheap.
Cons: More stuff to buy. Need to weld bung onto exhaust. Not sure how much vacuum it pulls; probably varies a lot setup to setup.

3. Vac pump + Hobbs switch
Pros: ???
Cons: Cost/effort/space requirements

4. Vent to atmosphere
Pros: Easy as hell.
Cons: No vacuum.


With any setup, you can choose to try to recover oil by the dipstick return, or you can plug it. Personal preference.

Tried #1 with an MANN Provent, but still had oil blowing through (I have a MAF) so I switched to 4 with the largest hose I could find.

I'm planning to add a big catch can with a breather at some point, but since I'm not pulling vacuum I want to restrict airflow as little as possible.


Also, I'm not sure what you mean by "Clean air intake."
If you're asking where the CCV air vents back into the intake, it's on the manifold for OBD2 cars.
If you're asking where the air enters the crankcase, it comes in as blow-by through the rings, gaskets, etc.

[ak-]

Option #3 and #4 will 100% work without worry.
#3 is documented on someone's build on bimmerforums f/i section and works amazingly. The same guy also tried option #2 with multiple different bung angles, and it still wouldn't work.

Nobody seems to have successfully done option #1 and #2 and documented it.
For whatever reason, not enough vac is pulled by the exhaust and crank pressurization still occurs. As for option #1, the cons mentioned by Northern exist plus oils introduced into the cylinders start leaning out mixtures/detonating especially over time.

I don't know what is it with these motors because I would LOVE to have my breather go into my intake without any ill effect like 2jz's and OEM manufactures.

[haaken675]

So even with a baffled catch can, I am likely to get oil in my intake going with option #1? I wonder if that is a result of just having a ton of vacuum...From what I understand, I could get a PCV valve that would limit the amount of vacuum pulled. I wonder if that would solve that problem?

I purchased a baffled catch can that an either be vented to atmosphere or ran inline to pull vacuum through. I might try running an inline PCV valve initially and see how that works, and if I notice oil in the intake piping, intercooler, etc. just vent it to atmosphere.

[ak-]

Limiting the amount of vac would just pressurize the crank case seeing that there is no where for it to travel when blocked/limited.

If the car is already tuned and you're adding the can inline after, pay attention to your AFR's since you're now introducing oil vapors to your combustion depending how good of a job the baffling does.
Or even better log the data.

[haaken675]

I don't see how limiting vacuum would create pressure vs simply venting to atmosphere. From what I can gather, this is how most turbo OEM cars do their pcv systems. From all the diagrams and documents related to various pcv valves, it looks like most of them have the ability to start limiting vacuum to reasonable amount in a high vacuum scenario, and then allow more flow when the car is idling. By virtue of being under vacuum, you cannot be creating pressure.

[Red_liner740]

I vent my turbo LS to atmosphere. Two 10an lines, one from each valve cover to a catch can with breather on top. 17 psi, 654whp.