how does the PVC system actually work or what does it do?
12-06-2002 | 03:25 PM
#1
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From: East Central Florida
Re: how does the PVC system actually work or what does it do? The ideas are to scavenge blowby gasses
from the crankcase, for several reasons:
- crankcase positive pressure increases
oil leaks
- blowby is partially combusted, high
pollution naughtiness
- blowby contaminates oil, adds light
hydrocarbons and corrosives
The PCV valve meters the airflow. I never
figured out the basis here. There is a fresh
air inlet and a suction exit, the PCV valve
is on the suction side. On our cars the
inlet is in the TB, the fitting is behind
the blade but the port passes through the
body and draws from before the blade. The PCV
air is after the MAF so any air drawn is
metered.
I did the TB P&P recently on an older core,
and there was a lot of sooty looking stuff
in turbulent areas (near the throttle shaft).
I think this is PCV inlet, going the wrong
way. I have a theory that some of the oil
consumption problem may be blowby, extracted
the wrong way (through the inlet line) under
WOT; under these conditions you have crankcase
pressure, high oil "fogging" in the top end,
and maximum suction in the tract between MAF
and TB (which is where the PCV make-up air
comes from). The intake airflow makes a
vacuum across the air cleaner and MAF.
So there exists the potential for some oil fog
and bad air to run backward in this line. This
is the only explanation I can come up with
for "tar" in the TB, distributed in obvious
airflow-directed patterns.
I have a notion to put one of those cheap
see-through fuel filters in the PCV inlet line,
just to see if this is what goes on. But my
car is too new to have a lot of blowby, yet.
PCV extracted gasses (and spooge) go into
the intake manifold right behind the TB, on
the passenger's side. PCV valve is "hidden"
inline near the intake manifold connection.
from the crankcase, for several reasons:
- crankcase positive pressure increases
oil leaks
- blowby is partially combusted, high
pollution naughtiness
- blowby contaminates oil, adds light
hydrocarbons and corrosives
The PCV valve meters the airflow. I never
figured out the basis here. There is a fresh
air inlet and a suction exit, the PCV valve
is on the suction side. On our cars the
inlet is in the TB, the fitting is behind
the blade but the port passes through the
body and draws from before the blade. The PCV
air is after the MAF so any air drawn is
metered.
I did the TB P&P recently on an older core,
and there was a lot of sooty looking stuff
in turbulent areas (near the throttle shaft).
I think this is PCV inlet, going the wrong
way. I have a theory that some of the oil
consumption problem may be blowby, extracted
the wrong way (through the inlet line) under
WOT; under these conditions you have crankcase
pressure, high oil "fogging" in the top end,
and maximum suction in the tract between MAF
and TB (which is where the PCV make-up air
comes from). The intake airflow makes a
vacuum across the air cleaner and MAF.
So there exists the potential for some oil fog
and bad air to run backward in this line. This
is the only explanation I can come up with
for "tar" in the TB, distributed in obvious
airflow-directed patterns.
I have a notion to put one of those cheap
see-through fuel filters in the PCV inlet line,
just to see if this is what goes on. But my
car is too new to have a lot of blowby, yet.
PCV extracted gasses (and spooge) go into
the intake manifold right behind the TB, on
the passenger's side. PCV valve is "hidden"
inline near the intake manifold connection.
12-07-2002 | 01:51 AM
#2
how does the PVC system actually work or what does it do? Ok im trying to fix it so it doesnt leak oil.
I need to understand it fully, in threory what is it there for?
how is it routed, why is it directed back into the intake?
I know it comes off the valve covers then to the pvc vavle (how does this work, how does it need to work for a boosted engine)
then back into the intake.
am i missing any thing?
I need to understand it fully, in threory what is it there for?
how is it routed, why is it directed back into the intake?
I know it comes off the valve covers then to the pvc vavle (how does this work, how does it need to work for a boosted engine)
then back into the intake.
am i missing any thing?
