When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Calm down whipper snapper. If you don't know the basic operations of an engine, don't respond. It just makes you look.... well.... JD's explanation is full of errors. You should know what those are and be able to correct him.
Yes please point out my errors so we can all learn. I have looked into our PCV system and gave my best understanding of how it functions. I would like to know where I went wrong if I did.
Pretty sure it is just a check valve from the crank case into the intake manifold. Check valve is open under vacuum and closed under boost. Under vacuum fresh air can only enter through the breather port on the valve cover. Under vacuum crank case air is sucked into the intake manifold and that air mass is replaced by blowby gasses and fresh air through the valve cover. As far as I know, the only metering mechanism is the orifice size in the head. The valve in the IM is simply a check valve and doesn't do any sort of metering.
Under boost no crank case air is inducted through the IM. The check valve is closed. Any excessive pressure is dumped through the valve cover port into the intake tract. No fresh air is introduced into the crank case at this time.
That's the only weird sentence, otherwise it's pretty much right. The LE5 doesn't have any valves at all, but your LSJ manifold should have one.
That's the only weird sentence, otherwise it's pretty much right. The LE5 doesn't have any valves at all, but your LSJ manifold should have one.
What I meant by that sentence is if air is going into the intake manifold from the crank case via the PCV port then air must be entering the crankcase from either the valve cover port and/or from blowby as I see no other source for air to enter the crank case. We know the crank case isn't holding vacuum so the air mass that goes into the intake manifold has to be replace by an equivalent air mass from either the valve cover or blowby but probably a mixture of both as there are no other crank case air inlets that I know of.
It's not just a check valve or one size would fit all. There are close to as many different PCV valves as there are engine designs.
It is not always open under vacuum if you are considering anything below atmospheric pressure vacuum. Being spring loaded one way as well as a specific weight, it takes a specific amount of vacuum to begin opening.
Closes under boost: It closes way before boost develops, again it is calibrated by a spring and a weighted plunger. Even the way it is inserted affects the flow. You will find many vertical or close to vertical so the weight is adding to the function.
Crank case air is not sucked in: Under vacuum, fresh filtered outside air is drawn into a specific area of the crankcase to be most effective in mixing with and drawing with it blow by gasses back into the combustion area to be re-burnt.
The orifice in the head is not the metering mechanism: The holes in the PCV valve, tension of the spring and weight of the plunger or valve that closes the passages is how metering is done.
The valve in the IM is simply a check valve and doesn't do any sort of metering. That could not be more false.
If you don't like any of this, just agree to disagree then.
It's not just a check valve or one size would fit all. There are close to as many different PCV valves as there are engine designs.
-ALL check valves have a certain spring weight. I was specifically referring to the LSJ PCV system
It is not always open under vacuum if you are considering anything below atmospheric pressure vacuum. Being spring loaded one way as well as a specific weight, it takes a specific amount of vacuum to begin opening.
-Again this is just due to the spring weight of the check valve. My comment was a generalization. Getting into the specific in-hg at which the PCV check valve opens is just being pedantic.
Closes under boost: It closes way before boost develops, again it is calibrated by a spring and a weighted plunger. Even the way it is inserted affects the flow. You will find many vertical or close to vertical so the weight is adding to the function.
-So you agree it closes under boost?
Crank case air is not sucked in: Under vacuum, fresh filtered outside air is drawn into a specific area of the crankcase to be most effective in mixing with and drawing with it blow by gasses back into the combustion area to be re-burnt.
-Air from the crank case doesn't enter the intake manifold?
The orifice in the head is not the metering mechanism: The holes in the PCV valve, tension of the spring and weight of the plunger or valve that closes the passages is how metering is done. -So this is the one part I got wrong. This assumption was based on the fact that my stock L61 intake manifold doesn't even have a check valve. On my stock L61 I am pretty sure the only metering is through an orifice. Whether that orifice is in the intake manifold or in the head I can't remember. I thought it was in the head and maybe this is where I went wrong. Is it in the intake manifold?
The valve in the IM is simply a check valve and doesn't do any sort of metering. That could not be more false
-Same point as above. My observations of the PCV valve were from blowing and sucking on it to test it. It didn't seem to meter flow. I would be interested in knowing how much the opening area of the valve actually changes from atmospheric to 20 in-hg
Same point as above. My observations of the PCV valve were from blowing and sucking on it to test it. It didn't seem to meter flow. I would be interested in knowing how much the opening of the valve actually changes from atmospheric to 20 in-hg[/B]
Yes, that is a basic old school way to test your removable PCV valve as long as you hold it the exact way it is inserted into the engine. Before there became hundreds of thousands of different PCV valves, AC made a tester that you set to the valves orifice size and placed over the oil filler hole. I have one on my antique shelf. It starts out orange and if the PCV was good it would pull into a Green zone. I saw one sell on Barrett Jackson for $115.00
Yes, that is a basic old school way to test your removable PCV valve as long as you hold it the exact way it is inserted into the engine. Before there became hundreds of thousands of different PCV valves, AC made a tester that you set to the valves orifice size and placed over the oil filler hole. I have one on my antique shelf. It starts out orange and if the PCV was good it would pull into a Green zone. I saw one sell on Barrett Jackson for $115.00
From my experimentation it seemed to act exactly like a weak check valve that didn't change restriction regardless of how hard I blew on it. Though I do not know how the pressure in my lungs compares to actual vacuum experienced in the manifold. Also, my mouth is not a precision instrument.
It's not just a check valve or one size would fit all. There are close to as many different PCV valves as there are engine designs.
-ALL check valves have a certain spring weight. I was specifically referring to the LSJ PCV system
It is not always open under vacuum if you are considering anything below atmospheric pressure vacuum. Being spring loaded one way as well as a specific weight, it takes a specific amount of vacuum to begin opening.
-Again this is just due to the spring weight of the check valve. My comment was a generalization. Getting into the specific in-hg at which the PCV check valve opens is just being pedantic.
Closes under boost: It closes way before boost develops, again it is calibrated by a spring and a weighted plunger. Even the way it is inserted affects the flow. You will find many vertical or close to vertical so the weight is adding to the function.
-So you agree it closes under boost?
Crank case air is not sucked in: Under vacuum, fresh filtered outside air is drawn into a specific area of the crankcase to be most effective in mixing with and drawing with it blow by gasses back into the combustion area to be re-burnt.
-Air from the crank case doesn't enter the intake manifold?
The orifice in the head is not the metering mechanism: The holes in the PCV valve, tension of the spring and weight of the plunger or valve that closes the passages is how metering is done. -So this is the one part I got wrong. This assumption was based on the fact that my stock L61 intake manifold doesn't even have a check valve. On my stock L61 I am pretty sure the only metering is through an orifice. Whether that orifice is in the intake manifold or in the head I can't remember. I thought it was in the head and maybe this is where I went wrong. Is it in the intake manifold?
The valve in the IM is simply a check valve and doesn't do any sort of metering. That could not be more false
-Same point as above. My observations of the PCV valve were from blowing and sucking on it to test it. It didn't seem to meter flow. I would be interested in knowing how much the opening area of the valve actually changes from atmospheric to 20 in-hg
I corrected your mistakes as you asked... Use the knowledge as you wish. I am a perfectionist so if you don't want answers that are specific, don't ask for them.
I corrected your mistakes as you asked... Use the knowledge as you wish. I am a perfectionist so if you don't want answers that are specific, don't ask for them.
Only part I got wrong potentially was the orifice vs. check valve metering. My L61 stock has NO check valve at all and does all it's metering through an orifice. I assumed this orifice was in the head but maybe it is actually in the intake manifold? Do you know?
The rest of the stuff was not wrong, it was just simplified beyond your liking.
Only part I got wrong potentially was the orifice vs. check valve metering.
That is its core function!! In the fewest words: It is a "one way calibrated air metering device". I was letting everything else slide till you blew that. Remember... It was you that asked for an explanation and now your saying you are correct and I am being pedantic.
My L61 stock has NO check valve at all and does all it's metering through an orifice. I assumed this orifice was in the head but maybe it is actually in the intake manifold? Do you know?
From my GM material, this is all I could find. I have not had one apart.
The L61 has the PCV control passages built in to the "Gasket" between the intake manifold and the cylinder head. This is about 3/16" thick, of moulded plastic. There are long squiggly channels in the surface with rubber seals around the edges. With that said, we are both running the LSJ PCV system now.
Do you realize as far as almost everyone in the forum is concerned it doesn't make a difference to them whether the metering is done via dynamic valve opening area or an orifice opening area, that the basic functionality is the same?
From my GM material, this is all I could find. I have not had one apart.
The L61 has the PCV control passages built in to the "Gasket" between the intake manifold and the cylinder head. This is about 3/16" thick, of moulded plastic. There are long squiggly channels in the surface with rubber seals around the edges. With that said, we are both running the LSJ PCV system now.
The "gasket" on an L61 intake manifold is just rubber inserted into the mating face of the manifold. It can't really be the gasket. The orifice must be in the intake manifold.
You still didn't answer my question. Do you even know if the orifice that meters the flow on 2.2 and 2.4 NA Ecotecs is in the head or the intake manifold?
Do you also realize as far as almost everyone in the forum is concerned it doesn't make a difference to them whether the metering is done via dynamic valve opening area or an orifice opening area, that the basic functionality is the same?
Ummm look above this post! I am not required to answer your questions. Would you like for me to ask you some?
The "gasket" on an L61 intake manifold is just rubber inserted into the mating face of the manifold. It can't really be the gasket. The orifice must be in the intake manifold.
From what I read it is part of the intake manifold also. Regardless, it is a moot point. You and I both are running the LSJ PVC system.
Like I said... I have never had one apart so all I can go by today is printed material.
I can see how any "metering" is going on. Flow may bounce around a little at spring tension and you are calling that metering. I think it's only an on off switch set by spring pressure. Sure the spring may actually restrict or meter flow at certain vacuum but I can't see that being the intent.
03-21-2018, 01:07 PM
