PCV--how exactly does it work?
PCV--how exactly does it work? I know what it does...but how? (i was thinking about it...how does the gas escape??)
How does the crank get vented from the valve covers on the LS1???
Thanks
Erik
How does the crank get vented from the valve covers on the LS1???
Thanks
Erik
Positive Cranckcase pressure. In a simplified way, your car produces a vacuum which is a negative pressure if not allowed to vent properly. If the motor was sealed up tight with no PCV valve or breather element, what happens is there is constant pressure on the bottom end of the motor which will cause rings to wear badly or blow out seals. By venting the vacuum either back into the intake (PCV) or breather (let it escape into atmostphere). The PCV valve is preset by GM to a certain amount of vacuum before it opens and allows the intake to pull the unwanted amount of vacum back into the combustion chamber to be used with the fuel and air mixture. Same as your evap system, when the fuel tank pressure builds to a certain amount the intake vacuum takes in the excess pressure to be used with the air fuel mixture. This is why it is better for the environment because it gets burned in the combustion chamber instead of going into the air. I hope this makes sense, I am sure there is a better way of explaining it. Let me know if there is anything you did not understand.
Last edited by 03 BUSA; Jan 27, 2007 at 01:42 PM.
cool..ok heres the deal...I originally capped off all PCV vents etc on my motor...and ran a Metco breather...
HOwever, I got to thinking...I like the idea of the POSITIVE PCV by way of the TB because it actually sucks the gases out, instead of it just escaping naturally through the breather...
SO, i took some tubing and reconnected the vent tube on the pass side valve cover to the TB....
however, I do not have a PCV valve....nor do I have a catch can..I am going to purchase a catch can for the oil problem, do I need to also add a PCV valve in that line or will I be ok?
Thanks
HOwever, I got to thinking...I like the idea of the POSITIVE PCV by way of the TB because it actually sucks the gases out, instead of it just escaping naturally through the breather...
SO, i took some tubing and reconnected the vent tube on the pass side valve cover to the TB....
however, I do not have a PCV valve....nor do I have a catch can..I am going to purchase a catch can for the oil problem, do I need to also add a PCV valve in that line or will I be ok?
Thanks
also, how exactly do the gases from the crankcase make it up into the valve covers to escape?? The gases cannot escape through the pistons correct?? I am unclear as to how a gas from the crank case MAKEs it to the valve cover....
any ideas..
any ideas..
The gasses get sucked in through the oil drainback holes in the heads. They build up in the crankcase and take the paths of least resistance...heading upwards through the block and towards the valve covers. Breathers are ok, I just like having a vacuum pulling the gasses out of the engine.
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03BUSA's information is incorrect, as far as the PCV system goes.
If the crankcase was completely sealed off, the pressure inside would constantly RISE. This is due to gasses bypassing the piston rings (blow-by). Eventually it would get to a point where the pressure would simply start to relieve itself by blowing out through the front and rear seals, valve cover seals, etc.
Now, the lines coming from the back of the valve covers that join together and plug into the MANIFOLD are where the crankcase gasses are routed into the incoming air charge. The MANIFOLD is at a slight vacuum (when the throttle is not open, AKA normal driving), due to the cylinders pulling air from it.
Now, will all this in place, the intake manifold (which is less than atmospheric) would be pulling a vacuum on the crankcase. Our cars, as well as nearly all others, have a line connecting the crankcase volume to an area downstream of the air filter, but upstream of the throttle body. This region is ALWAYS at atmospheric pressure. This line is called "the fresh air tube". The vacuum that the manifold has pulled on the crankcase is now pulling air into this tube from the outside, because the area where the tube from is AT atmospheric pressure.
So, as the car is idling, you can pull that hose connecting your throttle body to the valve cover (fresh air tube) off, and you'll feel a vacuum on the hose. If you were to do the same, but pull the line off the manifold, you'd feel nothing, but maybe some gasses trying to escape.
This system of pulling in fresh air, whilest pulling the combustion gasses/fresh air mixture OUT is called a PCV system. The problem is, that bits of oil go along for the ride out the tube and end up in the intake tract.
If the crankcase was completely sealed off, the pressure inside would constantly RISE. This is due to gasses bypassing the piston rings (blow-by). Eventually it would get to a point where the pressure would simply start to relieve itself by blowing out through the front and rear seals, valve cover seals, etc.
Now, the lines coming from the back of the valve covers that join together and plug into the MANIFOLD are where the crankcase gasses are routed into the incoming air charge. The MANIFOLD is at a slight vacuum (when the throttle is not open, AKA normal driving), due to the cylinders pulling air from it.
Now, will all this in place, the intake manifold (which is less than atmospheric) would be pulling a vacuum on the crankcase. Our cars, as well as nearly all others, have a line connecting the crankcase volume to an area downstream of the air filter, but upstream of the throttle body. This region is ALWAYS at atmospheric pressure. This line is called "the fresh air tube". The vacuum that the manifold has pulled on the crankcase is now pulling air into this tube from the outside, because the area where the tube from is AT atmospheric pressure.
So, as the car is idling, you can pull that hose connecting your throttle body to the valve cover (fresh air tube) off, and you'll feel a vacuum on the hose. If you were to do the same, but pull the line off the manifold, you'd feel nothing, but maybe some gasses trying to escape.
This system of pulling in fresh air, whilest pulling the combustion gasses/fresh air mixture OUT is called a PCV system. The problem is, that bits of oil go along for the ride out the tube and end up in the intake tract.
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Verdad Gallardo Hooking a line from the valve cover, to the throttle body, is the same as running a breather. It would just be a VENT.
The throttle body line comes out in FRONT of the throttle body BLADE, which keeps it constantly at atmospheric pressure, same as a breather. What you're doing now, is having a breather that just dumps into the intake stream. It's a CV, not a PCV.
The throttle body line comes out in FRONT of the throttle body BLADE, which keeps it constantly at atmospheric pressure, same as a breather. What you're doing now, is having a breather that just dumps into the intake stream. It's a CV, not a PCV.
Originally Posted by 03 BUSA
Dude, I just said the same thing you did, I just put it in a much simpler form that is all. So, do not tell them my post was incorrect. Thanks in advance.
You went back and edited your post after reading mine, don't you think we can see the time stamp? Stop trying to backpeddle.
Your post WAS incorrect, and now you're trying to be an amature keyboard warrior since your *** is hurting for some reason. A better approach would have been to say something along these lines. "Whoops, I misplaced a few terms, sorry". Me saying that your information was incorrect was not to be taken in a derogatory way.
BTW - Here's what you originally said. I went ahead and bolded the incorrect parts.
Positive Cranckcase pressure. In a simplified way, your car produces a vacuum which is a negative pressure. If the motor was sealed up tight with no PCV valve or breather element, what happens is there is constant vacuum on the bottom end of the motor which will cause rings to wear badly or blow out seals. By venting the vacuum either back into the intake (PCV) or breather (let it escape into atmostphere). The PCV valve is preset by GM to a certain amount of vacuum before it opens and allows the intake to pull the unwanted amount of vacum back into the combustion chamber to be used with the fuel and air mixture. Same as your evap system, when the fuel tank pressure builds to a certain amount the intake vacuum takes in the excess pressure to be used with the air fuel mixture. This is why it is better for the environment because it gets burned in the combustion chamber instead of going into the air. I hope this makes sense, I am sure there is a better way of explaining it. Let me know if there is anything you did not understand.
PS - Nobody likes a liar.
Originally Posted by 03 BUSA
Dude, I just said the same thing you did, I just put it in a much simpler form that is all. So, do not tell them my post was incorrect. Thanks in advance.
Originally Posted by 03 BUSA
Positive Cranckcase pressure. In a simplified way, your car produces a vacuum which is a negative pressure if not allowed to vent properly
Originally Posted by 03 BUSA
By venting the vacuum either back into the intake (PCV) or breather (let it escape into atmostphere).
Originally Posted by 03 BUSA
The PCV valve is preset by GM to a certain amount of vacuum before it opens and allows the intake to pull the unwanted amount of vacum back into the combustion chamber to be used with the fuel and air mixture. Same as your evap system, when the fuel tank pressure builds to a certain amount the intake vacuum takes in the excess pressure to be used with the air fuel mixture..
The basic concept of how I explained it was correct. As I stated in an unmodified post "I'm sure there is a beter way of explaining this" He had a better understanding of the system or what it is there for. Also, I have always been under the impression that a valve is something that opens and closes thus is whay I said the PCV opens at a predetermined pressure. I apoligize if my information was incorrect.
P.S. Do not call me a liar, Moderator or not.
P.S. Do not call me a liar, Moderator or not.
when I posted. I made a mistake as well..the tube I am running from the valve cover is going into the manifold..BEHIND the TB...sorry
That is why I like it, it actually IS pulling gases out rather than venting them because there is a constant vacuum when the car is running..
Blur, you are correct though about the TB tube, as that is in front of the blade, therefore, no vacuum is contstant...
Like I said...I run a breather to vent, and will run a tube + catch can from the pass valve cover outlet to the MANIFOLD on the pass side...I believe this will be more than sufficient in relieving crank pressure..
Busa---dude dont worry we make mistakes...thanks for your insight...dont take the ball busting personally
That is why I like it, it actually IS pulling gases out rather than venting them because there is a constant vacuum when the car is running..
Blur, you are correct though about the TB tube, as that is in front of the blade, therefore, no vacuum is contstant...
Like I said...I run a breather to vent, and will run a tube + catch can from the pass valve cover outlet to the MANIFOLD on the pass side...I believe this will be more than sufficient in relieving crank pressure..
Busa---dude dont worry we make mistakes...thanks for your insight...dont take the ball busting personally
Originally Posted by 2002/Black/SS
uuummmm i dont know what u guys are talking about, PCV is white plastic tubing. u guys are really stupid
PVC=polyvinyl chloride=pipes in your house
PCV=Positive Crankcase Ventilation
Might wanna take that statement back
.
Originally Posted by 2002/Black/SS
uuummmm i dont know what u guys are talking about, PCV is white plastic tubing. u guys are really stupid
yeah bro PVC is plastic tubing commonly used in house construction/plumbing...
Im talking PCV my man....
Originally Posted by LS69TA
We're stupd?
PVC=polyvinyl chloride=pipes in your house
PCV=Positive Crankcase Ventilation
Might wanna take that statement back .
PVC=polyvinyl chloride=pipes in your house
PCV=Positive Crankcase Ventilation
Might wanna take that statement back
.
Originally Posted by erikthegoalie
yeah bro PVC is plastic tubing commonly used in house construction/plumbing...
Im talking PCV my man....
Im talking PCV my man....
i have a nice pcv setup myself, and eric u knew i was kidding