Thread: Crank Case Ventilation fully explained. (Naturally aspirated edition.)

I have been keeping an eye on this thread for a while now. It had me searching other forums for more info. Cant wait until that proper Det diagram is finally done(very interested).
I have one question though, if your running an aftermarket can, do you run the pcv line to the can with the valve still in place? can you see any vacuum without the valve with the can also being connected to inlet pipe of the compressor housing?

I know it's been a while and the turbo edition needs more examples. I'll try to get to it soon.

I'm not sure what line you're talking about adding an aftermarket catch can to? Do you mean the smaller PCV line (not the WOT line)? If that is the case, then yes you absolutely want to leave the PCV valve in place if you do that. If you don't run the valve on an N/A car you could have situation where too much vacuum is placed on the engine. That valve controls flow and restricts flow during high vacuum situations. On a turbo or ram-air car obviously you need to to stop pressurizing the crankcase.
Your last question is better suited to the turbo edition. I'll post the answer over there.

Perfect example of how not to promote ring seal.

Ben, because of the breather filter coming off of the drivers side part of the valve cover rather than a hose with restrictor (old guys called them hogs tails and they are there to strap excess blow0by oils and gases, not to slow down air) being plumbed back into the intake on the metered air side of things?

Are you talking about what I've labeled the "fire suppressor" in my diagrams? It looks like a section of large metal pipe cleaner...

That's completely different from the restrictor in the diagram. Pictures of the actual restrictor can be seen in post #27: http://www.sr20-forum.com/448066-post27.html

Are we on the same page?




Also, reading your post again, you have a question mark at the end of the sentence, but I couldn't piece together a question from all the words. :o

Yes, "hogs tail". We were on the same volume, different chapter though.




"Perfect example of how not to promote ring seal"

What is the reason? Is the reason because of the breather filter coming off of the valve cover?

Yah, the breather is the reason for the lack of ring seal. No vacuum at all at high loads. However the real killer is removing the restrictor on that end. Without the restrictor, the small PCV line can't really build any vacuum in the crankcase either. So there's not going to be any vacuum at low loads either.

That's the epiphany I'm coming to. I'm finally realizing all of the reasons for those damn restrictors!

The smaller hose used on the WOT side (notice it fits inside the stock hoses) is also hurting flow out of the crankcase. The removal of the stock catch can doesn't hurt ring seal, but is just the icing on the cake.

This is a great example we can all learn from.

On a VE+T, when I ran somewhat similar setup as the picture (Valve cover went to a breather), I would end up with the passenger side of the engine full of oil. The dip stick would blow out and blow oil, and the valve cover gasket would start spraying oil. Basically higher RPM's of a VE like for no crank pressure. Once I attached the Valve Cover breather to the turbo intake, all problems where solved.

Another improper way to reroute the breather lines should be posted. This method was posted on the old forum, I ran it myself too, until Ben and I looked closer to the ventilation diagrams. He pointed out that I was basically negating the measures that Nissan implemented to reduce blow by.

Once again this is not the proper way to route the hoses!

Vadim, I wish I remember what we talked about when we decided that was not a good idea. All things considered, it is actually not that bad. I think the only issue I see is that it is overly complicated, costs money to implement, and all it does is run some of the blow-by through two oil separators instead of one. It limits flow a bit in the process though. So really not too bad, just sort of silly when you consider the stock setup already has an oil separator in the valve cover. Whoever came up with this idea () didn't seem to realize that one fact.

I remember the issue being is that as per FSM diagram blow by can go up the catch can and not only down. Thus you could be forcing crankcase blow by up into the valve cover directly to fight with the valve cover blowby.





Hey wasn't me . But I did learn something very valuable from that experiment. Nissan, with endless R&D resources, knows a little better then a single forum member with a Ghetto Engineering Degree.