Not your typical TBSS intake swap question

[that1dood]

So I have everything situated and ready to go except for one thing, any PCV system experts feel free to chime in...

On the stock truck manifold, the PS valve cover feeds directly into the manifold just behind the TB, but on the NNBS/TBSS set-up, its plumbed into the intake tube. I know most guys drill a hole into their intake tube and run a fitting from that to the PS valve cover when doing the NNBS/TBSS manifold swap, right? My thought/question is this: Would it be ok to plumb a fitting into the TBSS intake manifold directly aft of the throttle body instead of going the usual route and putting it between the MAF and TB on the intake tube? I know for the average joe, it's easier to drill the intake tube, but since I've shaved and relocated everything on the manifold already, why not move the PS PCV fitting to a more 'hidden' location? Does this fitting need to be before the TB because that's how it is in it's factory configuration on the new trucks? Or would it be ok to move it behind the TB like it is on our trucks in their factory configuration? Thanks for the input guys.

Erick

[coal miner]

Buy a oil cap filter and eliminate it.

[that1dood]

Ricky,

I thought about that for a while, but it was my understanding that our PCV system is a 'closed' system, so to speak. Correct me if I'm wrong, but wouldn't it be better to have the fresh air drawn in somewhere after the maf (vice drawing in unmetered air) so it's accounted for since it's essentially making it ways back into the manifold after it passes through the engine and out the DS valve cover into the intake manifold? Or are you suggesting check valve and filter on passenger side and catch-can then vent to atmosphere on driver side?

[coal miner]

You need fresh filtered are that's the point of the breather cap. My catch can is tied in on the driver side. Valve cover-catch can-intake is the way mine is. Passenger Side will be your air intake. Driver side will be the suction form intake manifold. After the oil cap filter is put on plug the hose form the passenger side. Driver side pvc hose will go to catch then the intake manifold. If no catch can is used the driver side pvc hose will just go back to the intake manifold ( suction). That the best I can explain it. Hope that helps you.

[that1dood]

ok so I understand your setup and how the air makes it's way from PS valve cover, through engine, out DS valve cover and into the intake but I think somewhere we got lost in translation. LOL

My concern is, doesn't the air going through the crankcase need to be metered (drawn into PS valve cover from somewhere after the MAF) since it's being fed back into the intake manifold and calculated into everything? I mean I guess not because it's common for guys to set their PCV up like you described... Maybe the amount of air actually going through the crankcase is way less than I'm imagining and it has a negligible impact on everything... I found this while looking for a definitive answer and thought it made pretty good sense... I bolded the part that raised this question in my head.

 

 

Some interesting info. Got this from another forum. Someone posted this from the intructions of their GM LS crate engine.

Positive Crankcase Ventilation System (PCV)
How the PVC system works:
A closed crankcase ventilation system should be used in order to provide a more complete scavenging of crankcase vapors. Filtered air
from the air induction system (air cleaner) duct is supplied to the crankcase, mixed with blow-by vapors, and passes through a crankcase
ventilation metering device before entering the intake manifold. The primary component in the positive crankcase ventilation (PCV) system
is the PCV flow metering orifice. Vacuum changes within the intake manifold result in flow variations of the blow-by vapors. If abnormal
operating conditions occur, the design of the PCV system permits excessive amounts of blow-by vapors to back flow through the crankcase
vent tube and into the engine induction system (air cleaner) to be consumed during normal combustion. This engine ventilation system
design minimizes oil consumption and significantly reduces the potential for oil ingestion during vehicle limit handling maneuvers.
How to set up your PVC system:
• There are three ports on the LSX long block that make up the PCV system. There are two foul side ports. Both of these ports should be
connected to the intake manifold and be exposed to vacuum at idle.
• The two ports are 1) Front port on the valley cover. 2) Left rear (driver) valve cover. These two silver tubes may look simple but, they should
not be modified. Both of the tubes have a small orifice within them that, is used in place of a PCV valve of early designs.
• There is one fresh air port which is on the front of the right (passenger) valve cover. Again this is a silver tube that faces forward on the valve
cover. This port should be connected to filtered clean air. This is typically within the engines air cleaner system or can be a separate air
filter if using a carburetor. If you are planning on an electronic fuel injections system that uses a mass air flow meter (MAF) then, the fresh
air to the PCV should be installed between the MAF and engine’s throttle body. The engine burns the air that enters the PCV system so,
if the fresh air port is prior to the MAF then, this air will enter the engine without being measured by the MAF.

[coal miner]

I really don't know about the metered part but I've never had any problems. Could fix that in your tune tho

Edited October 6, 2014 by coal miner (see edit history)

[GI.SS]

The air in the Pcv system does not need to be metered as it is to ventilate the crankcase pressure not provide the engine and supplemental air to provide power. Also note that when you go WOT your Pcv system actually reverses so if you don't have a check valve on your breather cap, you could push oil out of it. Ls2 engines are notorious for pushing the dipstick out the tube after a WOT run.

[AKSSS]

With a mass air flow setup it woul have a very small effect on your tuning. MOST people once they get to this point in power levels go to speed density. With speed density it doesn't matter how much air you pump into the intake. The map sensor would read the pressure diffrence.

 

Remind me of your setup? Didn't you just go turbo?

[onebadmax]

The MAF doesn't meter the pcv system. It's down stream of the sensor. All you are doing is venting the crankcase. You can vent to the atmosphere, but that is stinky and messy.

[that1dood]

I had a feeling the pcv didn't move enough air to really affect anything, so I think I'm just going to do the check valve and breather filter on the pass side to keep things simple. Thanks for the input guys. Still piecing together all the turbo stuff. Probably not going to be ready for that until I xfer to my next duty station... Right now I'm just headers, exhaust intake and tune.. my build is going a lot slower than I anticipated.

[teamvortec]

I added on fitting on the bottom of the intake tube and ran the drivers side hose to passenger side and tied them into together and then into tube.