Ah, this is true for a NA motor but since this is a forced induction motor, the intake manifold is under pressure, its a different scenario. If the blow by pressure is more than the than the manifold vacuum pull (which I assume will be the case in at maximum boost), the its going to be pushed back out the valve cover into the intake track. Thus the breather on the oil filler makes sense. Of course, the EPA would have a different view......

 

Forced induction (up to 21 lbs. of boost under the right conditions) is where I got my experience with the fresh air line flowing backwards under high RPM. I had 2 catch cans on my SRT4, one one the PCV side and the other on the fresh air side. The PCV side got much more oil but the fresh air side collected oil and had to be emptied also. The harder I ran the car the more oil in the fresh air side catch can.

 

Makes sense.

 

So if I go with the method of capping off the passengers side valve cover and run a breather cap, how is this compensated for as I am now introducing unmetered air into the motor?

 

A breather cap on the valve cover doesn't "introduce unmetered air" into the motor. The only air it lets in is filtered air into the crankcase (and oily air out of the crankcase into the atmosphere under high RPM), there's no metering of crankcase air.

You won't pass any visual inspections with a breather on the motor.

 

My understanding is that is does introduce unmetered air by the the air coming into the crankcase from the breather cap and then out of the drivers side valve cover and into the manifold. Meaning none of that air getting into the manifold ever passes the MAF sensor. Im not arguing with anyone. Just trying to understand.

 

There is no connection from the drivers side valve cover to the intake manifold.

The air into and out of the crankcase is NOT metered when you have a breather cap. It is metered stock since any air into the crankcase goes thru the MAF before it goes to the valve cover line.

Air path to the intake; From the filter to the MAF, then past the passenger valve cover line, then thru the throttle body, then past the PCV line then into the intake manifold. No drivers side connection at all.

 

Ok so as I understand it in the stock form, clean air is drawn in from the intake tract and pulled through the crankcase and out of the valley cover then into the intake manifold. I think we all can agree on that. Im my case with a maggie TVS blower, the valley cover vent is removed and now the drivers side valve cover vent is used for the dirty side air. This is connected to a port on the TVS blower. Hence now air is being introduced into the intake/blower that is coming from the crankcase vent and therefore is unmetered. Does this sound right?

 

That is true, and you can run either system, closed (i.e. catch can) or open (breather/PCV delete) but not both. This is a common mistake that many make, you cannot run a breather and still have your PCV system hooked up. You are creating an unmetered air source from the breather when you are drawing CC vapors into the TB.

 

I'm not familiar with supercharger setups, my turbo setups used the same PCV routing as stock with catch cans on both lines.

 

some guys talk about deleting the PCV on the LS2 as voodoo, well i have done that since i purchased my 06 LS2 with ten miles on the OD, and yes the hoses are hanging down on both sides of the motor, after four years and 90 thousand miles, the car has no irreversible wear and tear, the oil pump looked good, the pressure was fine, no rust of any kind in the lifters, rockers, no carbon build up in the valves, and specially no oil in the intake manifold...the engine was so clean that i decided to go one step further.

Last week i opened the engine up to install a set of LS3 heads and an LS3 Intake, and the usual stuff that goes with the installation, new PAC springs all GM gaskets, ARP bolts, new Melling oil pump, new comp push rods, but kept all the parts i saw that were in good shape, bolted her up and off i went to the dyno to get my WOT-AFR, and my drive ability back in shape....i have read countless hours of peoples opinions on them catch cans, i have friends that swear by them, but they all allow some oil to get into the Intake manifold....i know this for a fact, the friends that have these catch cans i have cleaned there throttle body with CRC throttle body cleaner and a good microfiber towel and i have gotten my hand as far as i can reach into the manifold and guess what! i have pulled the rag out all covered with oil....I also change my oil and filter every three thousand miles, plus i add some ZDDP Additive in the oil, and so far so good.....i think some one here is just trying to sell some catch cans...lol..JMO.

 

So why can't you run a breather along with the PCV system? In the setup I described the drivers side valve cover line acts as the dirty side and the breather would simply be the clean side. As far as unmetered air goes, in stock form the MAF is located after the clean side inlet so therefore all of that air getting into the motor would be unmetered.

 

Any other input?

 

Just started to look into PCV and catch cans (closed system) versus no PCV system (open system), and it seems one can run a filtered cap AND a catch can! And...at WOT, oil/fumes can never be forced into the intake via the "clean side" bellows from the right valve cover per the normal clean side setup...if the valve cover and the bellows are both capped like in DAL01's above photo.