Oil Catch Cans

[Husky65]

So I have a catch can I am about to install, and I was going to tee it into the pcv to manifold line.
However after a bit more thinking, this line is only under vacuum during normal driving right? At WOT, the valve in the pcv basically shuts yeah?

At WOT, the crankcase is venting through the valve cover to throttle body line yeah? Normally this is the crankcase fresh air inlet, but at WOT it reverses if I'm not mistaken.

So in a perfect world do you want 2 catchcans, one for the pcv to manifold, and one for the valve cover to intake?

I'm assuming the pcv to manifold is the one you should connect first, as most driving won't be done at WOT

[boofhead]

There are multiple strategies with a catch can. You are right normally you would have the catch can on the vacuum line from the manifold to the PCV valve. This will stop oil from entering the intake. The other side is a vent to allow air in to offset the vacuum. I see no need to have a catch can on that side.

[Husky65]

Yeah but at WOT the fresh air reverses, and the intake is actually sucking in from the valve cover, as opposed to the valve cover sucking in air from the intake under normal throttle.
I would imagine under WOT there would be a fair bit of oil fumes in the crankcase being sucked into the intake.

[hybrid]

I've always just vented the other side. Never had it connected to the intake (filter box?).

[Husky65]

The ford efi that I'm running has a vent nipple on the oil filler, which connects to a nipple on the throttle body. It has to be connected post MAF sensor if you are running one. That way when it sucks fresh air in through the PCV into the manifold, it is already metered.

In your case by having the fresh air being just a vent, it's not metered by the MAF, so wouldn't be the best way to go in my case with a MAF, as it's basically a big vacuum leak.

[hybrid]

Yeah forgot you're using MAF.
My Nissan was the same when it was MAF'd.

[Pinto-Pete]

Hmm Nissan, another word comes to mind for those that ends in d......

[nassi]

Hmm Nissan, another word comes to mind for those that ends in d......

Ah, you mean GOOD?

[Pinto-Pete]

Hmm Nissan, another word comes to mind for those that ends in d......

Ah, you mean GOOD?

Ahh no...