Thread: Finding a way to Reduce Oily Blow By Gases

If your drawthrough then having the VC blow by gasses be sucked in by the turbo seems to be the best. And no other modifications should be needed.

If blowthrough, you can have the turbo suck in the blowby, but you might need to get rid of the PCV valve.

This is the most consolidated spot for PCV info I've found yet:

DIYEFI.org Forum - View topic - Crank Case Ventilation

That's a pretty good article, and it goes back to what I've been basically saying.

Best setup is:


Now I do not agree with this setup for a few reasons:


1. Turbo helps suck out the pressure
2. If you vent the breather, unmetered air will get sucked into manifold via PCV

Vadim, you're right about the second setup you posted. Fred (the guy who wrote the article) did not have MAF cars in mind when writing it. He is deep in the world of engine management and has MAP sensors on the brain.

Additionally, the second setup you posted is also inferior to the first because like you said, you can maybe get some vacuum on the turbo inlet pipe to help with crankcase ventilation as in the first picture. If I remember correctly Fred recommends the first setup over the second, but he could have edited the post since I saw it last (or I could be remembering it incorrectly).

Neverless, I'm happy that the information that we gathered here locally (on this forum), is the same/very similar to what it actually is

So next step is a checkvalve oil cap

Glad I could help out

Another thing to consider about blowby is the lifespan of your oil. Blowby degrades oil faster by thinning it out. A bit of fuel vapor is part of the blowby. There are tons of reasons why you want to keep the crankcase pressure low: Helps rings seal better, increases mileage, decreases emissions, better oil life-span, reduced windage, reduced pumping losses, more power!

Say what?! You're chittin' me... I thought we were saying before that this setup is acceptable... Now you're telling me I have it backwards, and I need to remove that damn PCV at all costs?

It won't be much, will make your car run a little richer, so power wise you shouldn't have a problem. But when your trying to get down to efficiency and gas mileage, that's where you will see the difference.

I would remove my PCV, but then I would have to vent the breather, so then I would have to find another way for blow by gasses to be sucked out. At least currently the turbo does that. Now this is because I'm drawthough.

If your blow through you should be able to have the PCV disconnected and let the turbo suck in the blowby and then your blowby wont be metered .

Also corrected the PVC to PCV, I dunno how i got those mixed up

Tekkie, I understand your concern and am confused as well. You sure about that Vadim? The only problem I see with venting the breather to atmosphere is that you don't get the advantage of slight vacuum in the crank case at WOT or in boost. Also you're adding to your emissions, and in MAF equipped cars you will allow a small amount of metered air to leave the system.

I don't see how un-metered air will get sucked into the manifold ever.

Well the way I see it happening is, if your breather is vented, it may suck in some air from the outside, that will then get sucked into PCV into Intake Mani.

Now that would vary on how much blow by is present and how much vacuum is present.

I personally would love to cap off the PCV because of the oil that it brings into my manifold. But if it has some vapors with fuel then that should help with gas millage a bit. Once I figure finish some more stuff, I will be playing with blowby gases again