Thread: Confused with oil separator system

No more like this:



BTW just saw your Members Ride page, nice and clean car! Great job

I must have lost you with my description. Yes the pcv valve sucks in air from the valvecover at idle right? Well imagine if you have your oil cap off. You are basically making a vacuum leak. Air is pulled in from oil cap and through the pcv valve and into the intake mani.

Adding a pcv valve to the hose that goes before the turbo won't work. Even though the pcv valve is a one way valve, it simply cannot flow enough. Adding a one way valve, like an air pump check valve, would flow substantially more and keep the pcv from sucking in unmetered air at idle.

Understand? It is confusing to type but hopefully you can pick up from my description a lil better.

Any leak at the valvecover can potentially cause the car to run a lil lean, so having any unmetered air enter the valvecover can cause a lean condition.

This is exactly what I was talking about. Great job with the visual aid. As you can see here, this is the ideal setup. Adding a check valve in-line to the hose that goes from the catch can to the intake pipe will fix the lean idle condition. It may cause a slight hunt for idle occasionally, but it is rare.

So are you saying that by venting the blow by (that has no direct, pre ignition chamber connection, with metered intake manifold/intake pipe air) it is doing the same thing as a vacuum leak? If so I think then I get what you are saying.

The picture in my head has blow by always blowing out of the motor with combustion, unless the car is in boost, in which case the blow by can't properly vent through the PVC valve. At this point, because of the boost the valve is entirely closed.

Anyway if that's not right I think I give up I do agree on that last post by Vadim as being the best option too

This is EXACTLY how I have my setup.

So in order to run this setup, I would need a catch can with 2 ports on top and one on bottom, correct?

no, you need a catch can with two barbs on it. They should be on the side either next to each other, or opposite each other.


Also, the line from the VC to the IM should be run to the catch can, or eliminated completely, as under boost it will just create more pressure in the crankcase, and cause MORE oil to get trapped in the catch can, unless I'm totally missing the fact that it's not connected to the VC as a pcv hose...

EDIT: here's an acceptable catch can.

Look at Vadim's pictures. He shows that he has the return to the crankcase T'd. That's how you see that picture.

absolutely. At idle the pcv valve sucks in air from the vc. The vacuum in the manifold sucks in air through the pcv valve. Now imagine if your pcv valve were not inserted into the valve cover. At idle, the pcv valve will let unmetered air into the intake mani. This is the same as a vacuum leak.

But yes you are on the right track. Perhaps I could draw a picture.

Ok I get what you are talking about. I capped the line on the IM to get rid of that vacuum leak and vented the PVC valve.

I guess the best scenario would be to run the PVC valve to the separator line, and cap off intake manifold port.