PCV System w/ Boost and MAF Sensor?
04-08-2013, 02:04 PM
#1
PCV System w/ Boost and MAF Sensor? My tuner says that by running a breather where the oil filler cap is, and using the stock PCV system with a check valve, that is would basically be a vacuum leak. When out of boost, air would enter the breather (bypassing the MAF), go through the block, through the PCV system, and into the manifold to be burned... basically a vacuum leak since this air isn't been sensed by the MAF.
Now I thought that this "leak" could be accounted for in the tune, but my tuner says otherwise. So my question is, is there a way to run the MAF sensor and the PCV system where ALL of the air going into the engine passes through the MAF?
Instead of using the breather I could plumb the valve cover into the TB, but then in boost I would be pressurizing the block. A check valve in this line won't work unless it's closed when in boost with an electric signal (via a hobbs switch) or a vacuum operated valve uses vacuum to open the valve (similar to a BOV).
The only solution I see is to remove the PCV system and vent the block to atmosphere.
Now I thought that this "leak" could be accounted for in the tune, but my tuner says otherwise. So my question is, is there a way to run the MAF sensor and the PCV system where ALL of the air going into the engine passes through the MAF?
Instead of using the breather I could plumb the valve cover into the TB, but then in boost I would be pressurizing the block. A check valve in this line won't work unless it's closed when in boost with an electric signal (via a hobbs switch) or a vacuum operated valve uses vacuum to open the valve (similar to a BOV).
The only solution I see is to remove the PCV system and vent the block to atmosphere.
Last edited by Ferocity02; 04-08-2013 at 02:19 PM.
04-08-2013, 07:19 PM
#2
On The Tree
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From all the research i had done previously, i was under the impression that given large volumes of boost, we need to vent our engines somehow.
I bought a catch can and use the crankcase vent (i have an LS2 conversion) and duct that into the catch can with a breather filter which you'll see in this pic:
Some guys run the "breather port" back into their intake manifold:
I've also taken my driver side valve cover rearmost vent (by the brake booster) and i've run rubber hose to the front of my motor with an air/oil separator and another breather on the end.
You'll find lots of different setups with forced induction LS peeps. A basic search shows lots of information regarding increased crankcase pressures with forced induction. Easiest way to relieve that is to vent it to atmosphere.
I bought a catch can and use the crankcase vent (i have an LS2 conversion) and duct that into the catch can with a breather filter which you'll see in this pic:
Some guys run the "breather port" back into their intake manifold:
I've also taken my driver side valve cover rearmost vent (by the brake booster) and i've run rubber hose to the front of my motor with an air/oil separator and another breather on the end.
You'll find lots of different setups with forced induction LS peeps. A basic search shows lots of information regarding increased crankcase pressures with forced induction. Easiest way to relieve that is to vent it to atmosphere.
04-08-2013, 09:10 PM
#3
I've done tons of research on this as well, and have even made some diagrams. With a speed density tune the vacuum leak isn't a concern from what I can tell. But with a MAF sensor tune it is.
The second pic will not work as unmetered air enters the valve cover breather out of boost and ultimately makes its way back into the intake. That setup also wont work in boost unless there is a check valve built into the catch can.
The first pic would work with MAF, but you lose the benefit of having a vacuum source to continuously pull air out of the block when out of boost. And I'm not sure where that line to the valve cover goes, turbo inlet? I refuse to run any vent line to the turbo inlet after seeing the mess that it can cause working on turbo Volvos (which have catch cans).
One thing I'm confused about is that in a stock motor, some/most of the air that the PCV is letting into the intake is blowby and was only counted once by the MAF. How come it doesn't need to go back through the MAF?
The second pic will not work as unmetered air enters the valve cover breather out of boost and ultimately makes its way back into the intake. That setup also wont work in boost unless there is a check valve built into the catch can.
The first pic would work with MAF, but you lose the benefit of having a vacuum source to continuously pull air out of the block when out of boost. And I'm not sure where that line to the valve cover goes, turbo inlet? I refuse to run any vent line to the turbo inlet after seeing the mess that it can cause working on turbo Volvos (which have catch cans).
One thing I'm confused about is that in a stock motor, some/most of the air that the PCV is letting into the intake is blowby and was only counted once by the MAF. How come it doesn't need to go back through the MAF?
