Thread: Are Blow By Gasses Metered Air?

Are PCV and other Blow By gases metered air?

Blow by is not, and in the PCV system only the ventilation air from the intake is

Doesn't this belong in your other thread haha.

Haha and yes it does belong, but I was hoping someone else would contribute to the quick question because I doubt anyone will just read through 3 pages of the other thread

The air was metered at some point (when it was first drawn through the MAF sensor) but after it blows by the piston rings it isn't metered again if that's what you mean.

Yep thats pretty much what I was wondering.

I'll say this. On my car (1994) the blow-by air is not metered (re-enters the intake system after the MAF). On the Mustang in this PDF file, their blow-by air is metered. You need to check to see if the hose carrying the blow-by enters back into the intake system after/downstream the MAF (un-metered) or before/upstream the MAF (metered).

Normally, the blow by enters into the intake manifold, thus it is unmetered. In extreme conditions of large crankcase pressure, it travels back through the ventilation hose into the intake arm post maf, also unmetered. The only problem arises when the PCV valve is open and air is flowing through the engine in which can cause air that has been metered through the maf to flow through the ventilation hose and out the PCV valve (if is open to the atmosphere as mine was and not connected to manifold)

I think my Intake Mani is constantly pulling gas from the PCV valve, I guess that takes me back to the Vacuum leaks thread

Manifold vacuum on an NA engine is always drawing air through the engine as long as it's running. All a PCV valve does is 1) meters the amount of air being drawn through the engine, so as NOT to create a vacuum leak, and 2) prevents reverse flow in case of an intake backfire. Blow by gases WILL burn, and if exposed to backfire can blow the v/c, oil pan, etc. off the engine, as well as screw up a lot of other stuff. Plus, eventually these gases will go through the engine past the o2 sensor, affecting the a/f ratio, and therefore are metered.

If it is unmetered, can we put a filter on the valve cover T and call it a day?