Thread: Finding a way to Reduce Oily Blow By Gases

Oh no no I'm talking about the second black box, this one has a breather on it:



And wait, if it is after the maft that means it will take unmetered air

Double clutter! Ewwww!

Lol just a misunderstanding then, I meant that because it's between maf and TB, the air going into the VC is metered.

But the air going into mani from PCV may or may not be metered depending on the crankcase pressure. Either way, not a big deal lol.

Alright so to the pictures.

I first tried to block of the PCV valve and this is what I got...




Just capped off:



After about 2 minutes of idling:


As you can see it got a little bigger! I took it off right of way, I was scared it would shoot off and cause the car to stall while I'm driving.

Now I thought the intake manifold is supposed to have negative pressure


Here I am testing with capping off the part that goes into the Intake (this was done after I had failed at capping the PCV off)

Perhaps this is the cause? Due to the orientation of the capped line and the nature of the airflow through the manifold, maybe the inside of the cap is acting as a stagnation point and that is causing the bulge?

Thats weird!

I will try your method, take a hose and put a bolt through it. That should withstand any positive pressure hehe

Alright so I took a hose thats about 4" long and put a bolt in it then clamped it. That seems to be working pretty well.

Well see how it does on power/MPG.

Now I did notice that when I open the Oil cap, car runs normally but when I go to put down the oil cap it actually sucks it in! Interesting!

maybe I am wrong, but when you pull the pcv valve out of the vc with the engine running, you should have vacuum on the end of it. When the engine is operating wot the valve closes and excess crankcase pressure is routed into the intake tract instead of the manifold. At idle the crankcase should be kept to as close to a vacuum as possible.

Now one thing I have noticed with nissans is they have really high crankcase pressures compared to other cars. Take the oil cap off your car and you will see what I mean. You can feel the blowby gases blowing out, but on a well setup system you will be able to put a piece of paper over the oil fill hole and it won't be blown off.

I am not sure why the nissans are set up with so much pressure, just something I have noticed. Maybe that's why they use RTV gasket on everything lol.

Very interesting! I've noticed that too!

Now the first SR I've ever test driven, I was looking to buy one. It had a short ram intake almost directly on the throttle body, I don't recall seeing the maf!

Anyway, when I opened the oil cap on that car while idling, it would start stalling.

Now about having a lot of blowby, thats interesting we have 3 piston rings, and yet we still get more blow by then two piston ring motors eh?

I think it has to do with the pcv valve opening being designed small from the factory. For whatever reason nissan did this I have no clue...

Every car has blowby, but these nissans just like to have a lil more pressure in there I guess. Now typically you want as little pressure in the crankcase as possible to reduce windage and pumping losses. When I redesign this system it will work a lot better. Should gain some power too.