To PCV or not to PCV
04-25-2009, 06:52 AM
#161
Le Mans Master
My arguments are that PCV setups are for emissions reasons - especially when discussing a group of folks who [typically] take proper care of their vehicles. (My next thread is going to be on how pure nitrogen in tires is not necessary if you maintain proper tire inflation pressure...)
Will anyone in the PCV crowd agree that burning oil contaminated fuel will result in less HP than burning simply air and fuel mixture?
Again, here are some references to discussions about how to remove the oil in the PCV systems before it enters the intake. The problem is so widespread, that there's a MARKET for devices that prevent this phenomenon.
The first one is from this forum (and involves LSX engines!)
Link 1 - Corvette Forum Site
Read the second paragraph here
LS1 Tech guys have PCV problems
Even general auto forums are discussing this problem!
Ricers have the same problem
Here's a photo of the junk that passes through a PCV valve into your intake:
Without going back and reading every single post, I don't think this has been argued by the breather crowd, has it? At least, it's not one of mine...
Your statement, and SOME of your links, state that blowby wastes cause corrosion and spoil the oil, but fail to add the important clause "if left to sit in the crankcase." Your link to automotive tech books is a perfect example (Link Here) of what I am trying to point out. They mention products of combustion, moisture, and unburned fuel can combine with the oil and form harmful sludge if not removed. But note that they don't mention that 1) a PCV system is the only solution and 2) these are removed through normal oil changes and proper warming of the engine.
You clearly don't know about crankcase pressure. Any crankcase pressure due to blowby in a PROPERLY VENTED crankcase is so low that it can not cause oil leakage.
Not really. Once again, these vapors are only harmful if they are allowed to condense and remain in the crankcase.
No argument. A vacuum pump can create a vacuum of sufficient strength. A PCV system cannot.
This statement is moot if there are no oil leaks. If your engine has leaks, it isn't because you are running a breather setup. If you have a leak that is covered up by a PCV system, then you've got a vacuum leak and engine performance will suffer.
And at full open throttle, it will show zero hg (hopefully). Noonie's test is interesting but it doesn't show any flow. It is showing pressure.
Don't forget, to go from idle to 3000 rpm, I'll bet the throttle moves maybe 1/8 of an inch. Even with the PCV valve removed, you would see similar differences in pressure.
Now, if he were measuring flow, at idle there would be some flow. At 3000 there would be about the same amount if the PCV valve were working correctly. And at full throttle under a load, the flow would be maximum through the PCV, and it would REVERSE itself and be blowing OUT OF the intake breather.
Well, this is a TRUE statement! Notice the word virtually.
Do you not understand that a hole in the wall of a container equalizes the pressure between the two sides? During the time there is an explosion in a cylinder, the blowby will cause a brief period of time when the pressure in the crankcase will be somewhat higher. A fraction of a second later, the pressure is equalized due to the flow of gas through the hole which equalizes the pressure. The pressure is equal until the next cylinder fires.
A "closed" PCV system is one in which the intake tube is located within the air cleaner plenum so that the REVERSE FLOWING blowby is also directed into the incoming air stream. This is sort of like an additional EGR valve. Again, the reason to have a "closed" PCV system is purely for EMISSIONS, and this argument proves it. Do you disagree that an "open" PCV system has the identical effect on the crankcase as a "closed" system?
Here's one of thousands of links:
Closed vs. Open System
Again, notice the word "virtually". They are equal at all times except during the momentary firing of the charge in a cylinder. The breathers form a large "hole" in the crankcase, which allows the blowby to exit the crankcase and relieve the pressure. This happens so rapidly that it can be considered a continuous slow flow through the breathers, but at virtually no pressure differential.
Anyway, the only concern of a pressure differential is that oil might be forced out somewhere. Clearly, this is not the case and is of no concern in a properly built engine.
Finally, ff you need a visual, think of the Mississippi river at places in LA. It's got a difference in pressure upstream and downstream, but it's flowing so slowly it looks like a lake. The flow is imperceptible. People water ski on it. If the breathers were as small as a pinhole, you'd have your Niagra falls differential because the hole size is too small...
IBMPRC...
...but it's doubtful you've posted nearly enough links to have any of your points duly recognized.
BTW, raise your hand if you've ever found oil in the breather seeping from the "filter" where the crankcase "intake" vent hose connects. Guess what; that's evidence that the PCV valve is NOT sufficiently relieving pressure from blow by at all times, even if the PCV valve is operating properly. It shouldn't require reading an article on the internet to figure out that oil is in all probability due to flow to the breather rather than from it into the crankcase, for most of us anyway.
And another thing, if PCV's are so great at anything other than reducing emissions when compared with other methods of managing blow by, please to explain why they are NOT commonplace on bone fide racing engines? Well??
None of this is to say that PCV's are useless and that they don't have their place (so I take exception to being placed firmly in the "breather crowd"), but other than where required by law it is far overreaching to postulate that they are a necessity.
Get over it, already.
edit - Yes, I included Z-Mans entire quote to puff up my post, as it now has the added validity of having been found on the internet.
Last edited by TheSkunkWorks; 04-25-2009 at 07:06 AM.
04-25-2009, 10:16 AM
#162
Race Director
...but it's doubtful you've posted nearly enough links to have any of your points duly recognized.
BTW, raise your hand if you've ever found oil in the breather seeping from the "filter" where the crankcase "intake" vent hose connects. Guess what; that's evidence that the PCV valve is NOT sufficiently relieving pressure from blow by at all times, even if the PCV valve is operating properly. It shouldn't require reading an article on the internet to figure out that oil is in all probability due to flow to the breather rather than from it into the crankcase, for most of us anyway.
And another thing, if PCV's are so great at anything other than reducing emissions when compared with other methods of managing blow by, please to explain why they are NOT commonplace on bone fide racing engines? Well??
None of this is to say that PCV's are useless and that they don't have their place (so I take exception to being placed firmly in the "breather crowd"), but other than where required by law it is far overreaching to postulate that they are a necessity.
Get over it, already.
edit - Yes, I included Z-Mans entire quote to puff up my post, as it now has the added validity of having been found on the internet.
Had that several times in the past. Trucks, loaded, run at minimum vacumn just like wot, same conditions.
As you know the pcv system inlet side is supposed to reverse direction under heavy load, min vacumn conditions.
Ironcross made one of the brightest statements in this thread so far and that was if you are having blowby problems, then the engine is shot.
That is about all the evidence of oil in the air cleaner tells you.
The rest just falls under proper maintenance.
We ran them for many thousands of miles after that, it's just not practical to repair in all situations.
Now on a healthy engine;
I just changed the plugs on my wifes engine at 78,000mi for the 1st time and there was no evidence of oil, coking or anything detrimental. They just looked used, but clean as can be.
I could have a lot of other comments, but just don't have the energy for it now.
04-25-2009, 11:59 AM
#163
Racer
Member Since: Apr 2002
Location: Tuscaloosa AL
Posts: 353
Likes: 0
Received 0 Likes
on
0 Posts
If we're listing Pros and Cons, here's my list.
Pros of breathers only:
1) Reduces crankcase pressure
2) Blowby vapors emitted into the engine bay; not sucked back into the induction system (though nobody presented any evidence this causes any problems)
3) Some hot-rodders do it (as was reasoned in a previous post)
Cons
1) Crankcase pressure always higher than atmospheric pressure
2) Crankcase always full of harmful blowby gases
3) Oil leaks due to increased crankcase pressure vs. a PCV system
4) Pressure in the crankcase reduces HP
5) Reduced engine life
6) Corrosion of internal engine components
7) Reduced oil life
8) Oil's lubrication qualities reduced
Pros of PCV System
1) Fresh air replaces/dilutes harmful blowby gases.
2) Crankcase pressure lower than atmospheric pressure
3) Reduces oil leaks
4) Vacuum in the crankcase is good for horsepower and rings
5) Looks stock (5a) Fewer problems with state inspections
6) Better lubrication
7) Increases engine life
Cons
1) Blowby vapors returned to the induction system, though again, nobody has presented anything credible that indicates this is a problem.
Here's a thought. Is it possible that blowby gases are more combustible than raw air?
I'll finish with this. Try whatever you want. But the "breathers-only" crowd has much opinion; nothing to back it up. Everything I've stated above can be (and has been) supported with documentation.
Pros of breathers only:
1) Reduces crankcase pressure
2) Blowby vapors emitted into the engine bay; not sucked back into the induction system (though nobody presented any evidence this causes any problems)
3) Some hot-rodders do it (as was reasoned in a previous post)
Cons
1) Crankcase pressure always higher than atmospheric pressure
2) Crankcase always full of harmful blowby gases
3) Oil leaks due to increased crankcase pressure vs. a PCV system
4) Pressure in the crankcase reduces HP
5) Reduced engine life
6) Corrosion of internal engine components
7) Reduced oil life
8) Oil's lubrication qualities reduced
Pros of PCV System
1) Fresh air replaces/dilutes harmful blowby gases.
2) Crankcase pressure lower than atmospheric pressure
3) Reduces oil leaks
4) Vacuum in the crankcase is good for horsepower and rings
5) Looks stock (5a) Fewer problems with state inspections
6) Better lubrication
7) Increases engine life
Cons
1) Blowby vapors returned to the induction system, though again, nobody has presented anything credible that indicates this is a problem.
Here's a thought. Is it possible that blowby gases are more combustible than raw air?
I'll finish with this. Try whatever you want. But the "breathers-only" crowd has much opinion; nothing to back it up. Everything I've stated above can be (and has been) supported with documentation.
Second, I'm not sure why why, despite other potential engineering benefits, we can't agree that pcv (as a valved closed system) was originally implemented for two reasons: first, in tanks to eliminate potential water entry into the engine and, second, in the commercial automotive market to reduce smog-generating compounds from entering ambient air from automotive engines in California. I and at least one other have produced evidence for this as you requested.
As an aside for other concerned readers, baffled rocker covers, with filtered breathers eliminates the "oil on the valve covers" issue.
04-25-2009, 02:58 PM
#164
I want to tell all of you all that I find this subject fascinating, so keep posting replies.
My "Mopar" buddies that have hemis, none of them use PCV's - They use breathers in both valve covers that emit oil all over the motor. They put cotton wristbands around them to "Contain" the spillage.
They also complain of oil leaks on both the front and rear of their intake manifolds as well. Also leaks from dipsticks and intake gaskets.
I have had my 67 for 42 years and run a PCV valve and do not have to contend will these issues. Rock On!!
My "Mopar" buddies that have hemis, none of them use PCV's - They use breathers in both valve covers that emit oil all over the motor. They put cotton wristbands around them to "Contain" the spillage.
They also complain of oil leaks on both the front and rear of their intake manifolds as well. Also leaks from dipsticks and intake gaskets.
I have had my 67 for 42 years and run a PCV valve and do not have to contend will these issues. Rock On!!
04-25-2009, 07:03 PM
#165
Senior Member since 1492
04-25-2009, 09:58 PM
#167
Le Mans Master
Member Since: Apr 2000
Location: cincinnati ohio
Posts: 5,202
Likes: 0
Received 8 Likes
on
7 Posts
St. Jude Donor '09
Nope...
Prior to the early 1960s, automobile gasoline engines vented combustion gases directly to the atmosphere through a simple vent tube. Frequently this consisted of a pipe (the "road draft tube") that extended out from the crankcase down to the bottom of the engine compartment. The bottom of the pipe was open to the atmosphere, and was placed such that when the car was in motion a slight vacuum would be hopefully obtained, helping to extract combustion gases as they collected in the crankcase. The oil mist would also be discharged, resulting in an oily film being deposited in the middle of each travel lane on heavily-used roads. The system was not positive though, as gases could travel both ways, or not move at all, dependent on conditions. Most modern diesel engines still use this type of system to dispose of crankcase fumes.
Prior to the early 1960s, automobile gasoline engines vented combustion gases directly to the atmosphere through a simple vent tube. Frequently this consisted of a pipe (the "road draft tube") that extended out from the crankcase down to the bottom of the engine compartment. The bottom of the pipe was open to the atmosphere, and was placed such that when the car was in motion a slight vacuum would be hopefully obtained, helping to extract combustion gases as they collected in the crankcase. The oil mist would also be discharged, resulting in an oily film being deposited in the middle of each travel lane on heavily-used roads. The system was not positive though, as gases could travel both ways, or not move at all, dependent on conditions. Most modern diesel engines still use this type of system to dispose of crankcase fumes.
04-26-2009, 01:34 AM
#168
Melting Slicks
Good evening men! Did you miss me?
Z, I'll start with you.
1) You say: "My arguments are that PCV setups are for emissions reasons".
Don't know how many more times I can contend that PCV wasn't designed for emission purposes. Go back and read the difference between closed and open PCV systems. An open PCV system simply spewed vapors into the atmosphere; obvioulsy not an effort to reduce emissions. The closed system addressed that (the emission part) AND improved crankcase ventilation.
2) If the thought of blowby vapors being sucked into the intake bothers you that much, then fine, run a catch can. But the ongoing arguement to this point, has been Breathers vs. PCV, so your catch-can solution would need PCV system (or a vacuum pump) to function; right? Also, I don't know how much oil you figure on "catching" but after 3000 mile oil changes on my cars, oil usage is nearly zero. If you're catching too much liquid oil, you likely have inadequate or missing baffle(s).
3) You say: "Without going back and reading every single post, I don't think this (breathers are better at evacuating the crankcase) has been argued by the breather crowd, has it? At least, it's not one of mine..."
It's the arguement that's going into it's third week.
4) You say, " Your statement, and SOME of your links, state that blowby wastes cause corrosion and spoil the oil, but fail to add the important clause "if left to sit in the crankcase."
4a) And you say: "Once again, these vapors are only harmful if they are allowed to condense and remain in the crankcase"
With breathers only, please explain how blowby wastes are not left to 'sit in the crankcase'? What are the blowby wastes replaced with?
5) Oil leaks. Do you not believe vacuum in the crankcase helps reduce oil leaks?
6) You say: "A vacuum pump can create a vacuum of sufficient strength. A PCV system cannot."
It's been previously stipulated that vacuum pumps are superior. As far as 'suffiecient strength of a PCV system', I'll yeild to the GM engineers who designed these components. But how does this add to the breathers-only recomendation?
7) You say: "Noonie's test is interesting but it doesn't show any flow. It is showing pressure.".
No, it's showing vacuum, the key ingrediant to the PCV recipe.
8) You ask: "Do you not understand that a hole in the wall of a container equalizes the pressure between the two sides".
Incorrect. You forget that pressure is continually added to one of the two sides of the container (the crankcase).
9) You say: "They (atmospheric and crankcase pressure) are equal at all times except during the momentary firing of the charge in a cylinder."
All I'll say is, this statement will be added the 'greatest hits' list.
10) Your Mississippi river analogy. Not sure what you're pointing out.
Now on to you Skunk (good evening!).
11) You say: "Crankcase fumes are not as combustable as "clean air"
I don't know and you don't either. Here's a hypothetical lab test. Fill a balloon with blowby vapors (which includes unspent fuel) and fill a second balloon with raw air. Now hold a lighter to both and see which gives you the biggest bang. (You hold the balloon filled with blowby vapors and I'll hold the other).
12) You say: "WHO said that?"..
..to my request for evidence that Breathers are more effective at evacuating a crankcase of harmful blowby vapors than a PCV system. That's two in row now, you and Z, that apparently now agree, Breahters are inferior to a PCV system at the job of evacuating a crankcase of harmful blowby vapors.
13) You say: "IRRELEVANT"...
...to my statement that vacuum in a crankcase is better for HP than pressure. It's been argued ad naseum by the breather crowd that a PCV system hurts HP and/or Breathers help. I asked on about 44 occasions for the Breathers crowd to support that claim.
And now it's "irrelevant"?
14) You say: "A PCV system does not create crankcase vacuum. It's VENTED"
All I'll say is, take a look at exhibit 'A'; the photos presented by Noonie. One on your team believes those readings are pressure, but trust me, they're vacuum.
15) You say: "BECAUSE, he plugged theHOLE first."
...to Noonie's lab test. Once the "hole" is "unplugged" what would pull fresh air into the crankcase? (It starts with "V").
16) You say: "Their only eqyual with a HOLEsuch as a PCV fresh air intake OR a breather."
I can't argue for or against that statement because I don't understand it.
17) You say: "...if PCV's are so great at anything other than reducing emissions when compared with other methods of managing blow by, please to explain why they are NOT commonplace on bone fide racing engines? Well??"
First, see number 1 above. Second, I agree (see my prior posts, specifically on page 5 of this thread), most real race cars don't use a factory PCV system but most don't use a pair of breahters either. Most use a vacuum pump to reduce crankcase pressure and to remove blowby wastes.
You guys are getting off topic. Your arguement for these last two weeks is that breathers are better than a PCV system. Stay focused men.
On to you Mark (my Bama correspondent. Thanks for the complement and thanks to those who've PM'd me).
18) You questioned my question: "Here's a thought. Is it possible that blowby gases are more combustible than raw air?"
See number 11 above.
19) You say: "...and, second, in the commercial automotive market to reduce smog-generating compounds from entering ambient air from automotive engines in California."
See number 1 above
Thanks everybody! See you again tomorrow night.
Z, I'll start with you.
1) You say: "My arguments are that PCV setups are for emissions reasons".
Don't know how many more times I can contend that PCV wasn't designed for emission purposes. Go back and read the difference between closed and open PCV systems. An open PCV system simply spewed vapors into the atmosphere; obvioulsy not an effort to reduce emissions. The closed system addressed that (the emission part) AND improved crankcase ventilation.
2) If the thought of blowby vapors being sucked into the intake bothers you that much, then fine, run a catch can. But the ongoing arguement to this point, has been Breathers vs. PCV, so your catch-can solution would need PCV system (or a vacuum pump) to function; right? Also, I don't know how much oil you figure on "catching" but after 3000 mile oil changes on my cars, oil usage is nearly zero. If you're catching too much liquid oil, you likely have inadequate or missing baffle(s).
3) You say: "Without going back and reading every single post, I don't think this (breathers are better at evacuating the crankcase) has been argued by the breather crowd, has it? At least, it's not one of mine..."
It's the arguement that's going into it's third week.
4) You say, " Your statement, and SOME of your links, state that blowby wastes cause corrosion and spoil the oil, but fail to add the important clause "if left to sit in the crankcase."
4a) And you say: "Once again, these vapors are only harmful if they are allowed to condense and remain in the crankcase"
With breathers only, please explain how blowby wastes are not left to 'sit in the crankcase'? What are the blowby wastes replaced with?
5) Oil leaks. Do you not believe vacuum in the crankcase helps reduce oil leaks?
6) You say: "A vacuum pump can create a vacuum of sufficient strength. A PCV system cannot."
It's been previously stipulated that vacuum pumps are superior. As far as 'suffiecient strength of a PCV system', I'll yeild to the GM engineers who designed these components. But how does this add to the breathers-only recomendation?
7) You say: "Noonie's test is interesting but it doesn't show any flow. It is showing pressure.".
No, it's showing vacuum, the key ingrediant to the PCV recipe.
8) You ask: "Do you not understand that a hole in the wall of a container equalizes the pressure between the two sides".
Incorrect. You forget that pressure is continually added to one of the two sides of the container (the crankcase).
9) You say: "They (atmospheric and crankcase pressure) are equal at all times except during the momentary firing of the charge in a cylinder."
All I'll say is, this statement will be added the 'greatest hits' list.
10) Your Mississippi river analogy. Not sure what you're pointing out.
Now on to you Skunk (good evening!).
11) You say: "Crankcase fumes are not as combustable as "clean air"
I don't know and you don't either. Here's a hypothetical lab test. Fill a balloon with blowby vapors (which includes unspent fuel) and fill a second balloon with raw air. Now hold a lighter to both and see which gives you the biggest bang. (You hold the balloon filled with blowby vapors and I'll hold the other).
12) You say: "WHO said that?"..
..to my request for evidence that Breathers are more effective at evacuating a crankcase of harmful blowby vapors than a PCV system. That's two in row now, you and Z, that apparently now agree, Breahters are inferior to a PCV system at the job of evacuating a crankcase of harmful blowby vapors.
13) You say: "IRRELEVANT"...
...to my statement that vacuum in a crankcase is better for HP than pressure. It's been argued ad naseum by the breather crowd that a PCV system hurts HP and/or Breathers help. I asked on about 44 occasions for the Breathers crowd to support that claim.
And now it's "irrelevant"?
14) You say: "A PCV system does not create crankcase vacuum. It's VENTED"
All I'll say is, take a look at exhibit 'A'; the photos presented by Noonie. One on your team believes those readings are pressure, but trust me, they're vacuum.
15) You say: "BECAUSE, he plugged theHOLE first."
...to Noonie's lab test. Once the "hole" is "unplugged" what would pull fresh air into the crankcase? (It starts with "V").
16) You say: "Their only eqyual with a HOLEsuch as a PCV fresh air intake OR a breather."
I can't argue for or against that statement because I don't understand it.
17) You say: "...if PCV's are so great at anything other than reducing emissions when compared with other methods of managing blow by, please to explain why they are NOT commonplace on bone fide racing engines? Well??"
First, see number 1 above. Second, I agree (see my prior posts, specifically on page 5 of this thread), most real race cars don't use a factory PCV system but most don't use a pair of breahters either. Most use a vacuum pump to reduce crankcase pressure and to remove blowby wastes.
You guys are getting off topic. Your arguement for these last two weeks is that breathers are better than a PCV system. Stay focused men.
On to you Mark (my Bama correspondent. Thanks for the complement and thanks to those who've PM'd me).
18) You questioned my question: "Here's a thought. Is it possible that blowby gases are more combustible than raw air?"
See number 11 above.
19) You say: "...and, second, in the commercial automotive market to reduce smog-generating compounds from entering ambient air from automotive engines in California."
See number 1 above
Thanks everybody! See you again tomorrow night.
Last edited by 73, Dark Blue 454; 04-27-2009 at 10:16 PM.
04-26-2009, 07:37 AM
#169
Burning Brakes
Member Since: Dec 2007
Posts: 952
Likes: 0
Received 0 Likes
on
0 Posts
"I can't argue for or against that statement because I don't understand it."
At least you admit you don't understand how it works. That is why I can't argue with you any more. You REALLY don't get it, and never will.
Go have a coke on me. When you suck on the straw, see how much "vacuum" you can measure in the container.
At least you admit you don't understand how it works. That is why I can't argue with you any more. You REALLY don't get it, and never will.
Go have a coke on me. When you suck on the straw, see how much "vacuum" you can measure in the container.
04-26-2009, 07:58 AM
#170
Burning Brakes
Member Since: Dec 2007
Posts: 952
Likes: 0
Received 0 Likes
on
0 Posts
In closing, try to wrap your head around this.
There is no such thing as vacuum, it's merely the "absence" of atmospheric pressure.(Modern cars use a MAP sensor, not a vacuum sensor).
A "vacuum" gauge is merely a "pressure" gauge set to zero at atmospheric pressure.
ZERO represents atmospheric pressure, and less than zero represents low pressure.
Open a can of coke. Thats a "vented" container. Now insert a straw and suck.
That's a PCV system. You are creating low pressure in your mouth, and atmospheric pressure is forcing the liquid down in the container, and into your mouth.
See if you can measure any "vacuum" in the container.
As for crankcase fumes being more combustable than air, in your words, show me one link to any car on earth that has had an explosion, or rather a fire, in the crankcase.
There is no such thing as vacuum, it's merely the "absence" of atmospheric pressure.(Modern cars use a MAP sensor, not a vacuum sensor).
A "vacuum" gauge is merely a "pressure" gauge set to zero at atmospheric pressure.
ZERO represents atmospheric pressure, and less than zero represents low pressure.
Open a can of coke. Thats a "vented" container. Now insert a straw and suck.
That's a PCV system. You are creating low pressure in your mouth, and atmospheric pressure is forcing the liquid down in the container, and into your mouth.
See if you can measure any "vacuum" in the container.
As for crankcase fumes being more combustable than air, in your words, show me one link to any car on earth that has had an explosion, or rather a fire, in the crankcase.
04-26-2009, 08:20 AM
#171
Le Mans Master
crancase explosions
As for crankcase fumes being more combustable than air, in your words, show me one link to any car on earth that has had an explosion, or rather a fire, in the crankcase.
ok.....1957 gmc pick up trucks with the pontiac v8.....i was a wash boy for haydocy pontiac back in the day and it was a problem and on 3 or 4 occasions i remember the mechanics installing new oil pans on the pick ups that had blown the side rails off the pans...it is un related to this discussion because it was found many of the trucks were equipped with faulty fuel pumps but it can happen......pcv means positive crankcase ventilation....the engine sucks its own blow by to a degree depending on how much blow by you are discussing and the condition of the mill. i dont think anyone can argue that it is better than proper breathers especially at high rpm...it is cleaner for the enviornment though and was one of if not the first forms of smog control. the argument could also be made that the oil fumes are beneficial for the intake valves as an added lubricant and it does keep the garage floor a lot cleaner and also our roads....
ok.....1957 gmc pick up trucks with the pontiac v8.....i was a wash boy for haydocy pontiac back in the day and it was a problem and on 3 or 4 occasions i remember the mechanics installing new oil pans on the pick ups that had blown the side rails off the pans...it is un related to this discussion because it was found many of the trucks were equipped with faulty fuel pumps but it can happen......pcv means positive crankcase ventilation....the engine sucks its own blow by to a degree depending on how much blow by you are discussing and the condition of the mill. i dont think anyone can argue that it is better than proper breathers especially at high rpm...it is cleaner for the enviornment though and was one of if not the first forms of smog control. the argument could also be made that the oil fumes are beneficial for the intake valves as an added lubricant and it does keep the garage floor a lot cleaner and also our roads....
04-26-2009, 08:22 AM
#172
Le Mans Master
i noticed that picture of the oil separator in the pcv line. i asked about that pages and pages ago. at one point i had one of those on my old mustang. after a year of daily driving it was half full of oil. nice
04-26-2009, 08:27 AM
#173
Le Mans Master
04-26-2009, 09:30 AM
#174
Race Director
In closing, try to wrap your head around this.
There is no such thing as vacuum, it's merely the "absence" of atmospheric pressure.(Modern cars use a MAP sensor, not a vacuum sensor).
A "vacuum" gauge is merely a "pressure" gauge set to zero at atmospheric pressure.
ZERO represents atmospheric pressure, and less than zero represents low pressure.
Open a can of coke. Thats a "vented" container. Now insert a straw and suck.
That's a PCV system. You are creating low pressure in your mouth, and atmospheric pressure is forcing the liquid down in the container, and into your mouth.
See if you can measure any "vacuum" in the container.
As for crankcase fumes being more combustable than air, in your words, show me one link to any car on earth that has had an explosion, or rather a fire, in the crankcase.
There is no such thing as vacuum, it's merely the "absence" of atmospheric pressure.(Modern cars use a MAP sensor, not a vacuum sensor).
A "vacuum" gauge is merely a "pressure" gauge set to zero at atmospheric pressure.
ZERO represents atmospheric pressure, and less than zero represents low pressure.
Open a can of coke. Thats a "vented" container. Now insert a straw and suck.
That's a PCV system. You are creating low pressure in your mouth, and atmospheric pressure is forcing the liquid down in the container, and into your mouth.
See if you can measure any "vacuum" in the container.
As for crankcase fumes being more combustable than air, in your words, show me one link to any car on earth that has had an explosion, or rather a fire, in the crankcase.
The accepted definition of vacuum is 'any space with less than atmospheric pressure', not to be confused with 'absolute vacuum which is a theory on earth only' and cannot be produced on earth.
I have never heard anyone say "I cleaned the house today with my low atmospheric pressure cleaning device'.
I don't see the analogy between the vented coke can and the vented crankcase. You can't get coke thru sucking a straw in the can if the straw isn't immersed into the coke. After all the pcv valve isn't immersed into the crankcase.
The pcv valve is designed to close instantly upon backfire, to prevent 'what' and 'where'?
BTW, I found I have been spelling vacuum wrong most of the time.
04-27-2009, 11:24 PM
#175
Melting Slicks
Midyearvette. The discussion regarding the combustility of blowby vapors has to do with the combustibility in the combustion chamber; not the crankcase. Although, the PCV valve is designed as a flame retardent in addition to all it's other duties (what a beautifully engineered little device).
From here:
http://www.customefis.com/emissions.html
...is a direct quote:
"The PCV valve is a check valve that prevents a backfire from igniting the fumes inside the engine. Without a PCV valve, you risk an explosion inside your engine if the fumes inside the engine ignite. The fumes inside the engine come from what is called blowby. Blowby is the explosive gasoline and air mixture that gets past the piston rings inside the cylinders."
The Breathers-Only crowd has claimed that blowby vapors are less combustible than fresh air and therefore would reduce HP if introduced to the intake charge. Of course, nothing was ever presented as evidence, and I countered their theory with a question, "Is it possible blowby vapors are more combustible (in the combustion chamber) than fresh air?" (See my hypothetical lab test regarding two balloons above).
FB007, I admire your dedication but think little of your ability to comprehend.
You say (in your coke can & straw example): "You are creating low pressure in your mouth, and atmospheric pressure is forcing the liquid down in the container, and into your mouth."
"Atmospheric pressure is forcing liquid into your mouth?" Wow.
I'll try to explain a PCV system on your terms; your coke can analogy (not the best example, but here we go).
Imagine the liquid cola as the blowby wastes, the straw as the hose from the valve cover to the caruretor base, and the opening in the can around the straw as the breather element (usually attached to a fresh-air source in the air-cleaner in a PCV system). And the coke can as the crankcase.
As the liquid cola is sucked through the straw, what replaces the LC in the can? Fresh air, right? What pulls the fresh air into the coke can as the liquid cola is sucked out?
I'll give you a clue. It starts with a "V".
As the cola is sucked out, there's vacuum (relative to atmospheric pressure) in the can above the liquid cola.
What if there were not a source for fresh air (another key ingrediant to the PCV recipe)? What if the straw fit air-tight into the coke can with no other holes in the can? You couldn't suck anything out (without collapsing the can). Right? You'd have no fresh-air flow through your can (or crankcase).
That's a 6th grade explanation of how a PCV system works. Of course blowby vapors aren't liquid, the PCV valve regulates the whole process, blowby is continually pumped into the crankcase, etc.
Back to your engine. With the same coke can and straw, blow through the straw (the air forced through the straw represents blowby). The opening in the can that surrounds the straw are your breathers. Your can will always be full of blowby wastes as long as you blow (engine is running); fresh air can't get into the can (crankcase) to displace the blowby vapors.
But please, don't take my word for it. Do your own homework. Go back and read from any of the 25~ links previously posted, or here are 10 more links and explanations from other automotive forums:
http://forum.miata.net/vb/showthread...=323418&page=1
http://www.hotrodders.com/forum/pcv-...open-8413.html
http://forums.corvetteforum.com/c3-t...-breather.html http://forums.hotrod.com/70/1450116/...ure/index.html
http://www.jalopyjournal.com/forum/s....php?p=1422018
http://www.camaros.net/forums/showthread.php?p=147913
http://www.stevesnovasite.com/forums...ad.php?t=68411
http://www.camaros.net/forums/showthread.php?t=155656
http://www.hotrodders.com/forum/pcv-...ary-61826.html
http://www.hotrodders.com/forum/valv...rs-133842.html
http://www.jalopyjournal.com/forum/s...ad.php?t=87806
From here:
http://www.customefis.com/emissions.html
...is a direct quote:
"The PCV valve is a check valve that prevents a backfire from igniting the fumes inside the engine. Without a PCV valve, you risk an explosion inside your engine if the fumes inside the engine ignite. The fumes inside the engine come from what is called blowby. Blowby is the explosive gasoline and air mixture that gets past the piston rings inside the cylinders."
The Breathers-Only crowd has claimed that blowby vapors are less combustible than fresh air and therefore would reduce HP if introduced to the intake charge. Of course, nothing was ever presented as evidence, and I countered their theory with a question, "Is it possible blowby vapors are more combustible (in the combustion chamber) than fresh air?" (See my hypothetical lab test regarding two balloons above).
FB007, I admire your dedication but think little of your ability to comprehend.
You say (in your coke can & straw example): "You are creating low pressure in your mouth, and atmospheric pressure is forcing the liquid down in the container, and into your mouth."
"Atmospheric pressure is forcing liquid into your mouth?" Wow.
I'll try to explain a PCV system on your terms; your coke can analogy (not the best example, but here we go).
Imagine the liquid cola as the blowby wastes, the straw as the hose from the valve cover to the caruretor base, and the opening in the can around the straw as the breather element (usually attached to a fresh-air source in the air-cleaner in a PCV system). And the coke can as the crankcase.
As the liquid cola is sucked through the straw, what replaces the LC in the can? Fresh air, right? What pulls the fresh air into the coke can as the liquid cola is sucked out?
I'll give you a clue. It starts with a "V".
As the cola is sucked out, there's vacuum (relative to atmospheric pressure) in the can above the liquid cola.
What if there were not a source for fresh air (another key ingrediant to the PCV recipe)? What if the straw fit air-tight into the coke can with no other holes in the can? You couldn't suck anything out (without collapsing the can). Right? You'd have no fresh-air flow through your can (or crankcase).
That's a 6th grade explanation of how a PCV system works. Of course blowby vapors aren't liquid, the PCV valve regulates the whole process, blowby is continually pumped into the crankcase, etc.
Back to your engine. With the same coke can and straw, blow through the straw (the air forced through the straw represents blowby). The opening in the can that surrounds the straw are your breathers. Your can will always be full of blowby wastes as long as you blow (engine is running); fresh air can't get into the can (crankcase) to displace the blowby vapors.
But please, don't take my word for it. Do your own homework. Go back and read from any of the 25~ links previously posted, or here are 10 more links and explanations from other automotive forums:
http://forum.miata.net/vb/showthread...=323418&page=1
http://www.hotrodders.com/forum/pcv-...open-8413.html
http://forums.corvetteforum.com/c3-t...-breather.html http://forums.hotrod.com/70/1450116/...ure/index.html
http://www.jalopyjournal.com/forum/s....php?p=1422018
http://www.camaros.net/forums/showthread.php?p=147913
http://www.stevesnovasite.com/forums...ad.php?t=68411
http://www.camaros.net/forums/showthread.php?t=155656
http://www.hotrodders.com/forum/pcv-...ary-61826.html
http://www.hotrodders.com/forum/valv...rs-133842.html
http://www.jalopyjournal.com/forum/s...ad.php?t=87806
Last edited by 73, Dark Blue 454; 04-28-2009 at 01:10 AM.
04-28-2009, 08:59 AM
#176
Burning Brakes
Member Since: Dec 2007
Posts: 952
Likes: 0
Received 0 Likes
on
0 Posts
FB007, I admire your dedication but think little of your ability to comprehend.
You say (in your coke can & straw example): "You are creating low pressure in your mouth, and atmospheric pressure is forcing the liquid down in the container, and into your mouth."
"Atmospheric pressure is forcing liquid into your mouth?" Wow.Yes. That's how it REALLY works
I'll try to explain a PCV system on your terms; your coke can analogy (not the best example, but here we go).
Imagine the liquid cola as the blowby wastes, the straw as the hose from the valve cover to the caruretor base, and the opening in the can around the straw as the breather element (usually attached to a fresh-air source in the air-cleaner in a PCV system). And the coke can as the crankcase.
As the liquid cola is sucked through the straw, what replaces the LC in the can? Fresh air, right? What pulls the fresh air into the coke can as the liquid cola is sucked out? Wrong
I'll give you a clue. It starts with a "V". Also wrong
As the cola is sucked out, there's vacuum (relative to atmospheric pressure) in the can above the liquid cola.Wrong again. Since the can is vented, atmospheric pressure resides there.
What if there were not a source for fresh air (another key ingrediant to the PCV recipe)? What if the straw fit air-tight into the coke can with no other holes in the can? You couldn't suck anything out (without collapsing the can). Right? Nope. EXTERNAL pressure crushes the can, since there is insufficient pressure inside the vessal to support the can walls. Do you think submarines get crushed because they have a vacuum inside, or low presure vs. external pressure?
04-28-2009, 09:19 AM
#177
Team Owner
This can go on for ever if you start dissecting the meaning of words.
The accepted definition of vacuum is 'any space with less than atmospheric pressure', not to be confused with 'absolute vacuum which is a theory on earth only' and cannot be produced on earth.
I have never heard anyone say "I cleaned the house today with my low atmospheric pressure cleaning device'.
I don't see the analogy between the vented coke can and the vented crankcase. You can't get coke thru sucking a straw in the can if the straw isn't immersed into the coke. After all the pcv valve isn't immersed into the crankcase.
The pcv valve is designed to close instantly upon backfire, to prevent 'what' and 'where'?
BTW, I found I have been spelling vacuum wrong most of the time.
The accepted definition of vacuum is 'any space with less than atmospheric pressure', not to be confused with 'absolute vacuum which is a theory on earth only' and cannot be produced on earth.
I have never heard anyone say "I cleaned the house today with my low atmospheric pressure cleaning device'.
I don't see the analogy between the vented coke can and the vented crankcase. You can't get coke thru sucking a straw in the can if the straw isn't immersed into the coke. After all the pcv valve isn't immersed into the crankcase.
The pcv valve is designed to close instantly upon backfire, to prevent 'what' and 'where'?
BTW, I found I have been spelling vacuum wrong most of the time.
04-28-2009, 09:45 AM
#178
Burning Brakes
Member Since: Dec 2007
Posts: 952
Likes: 0
Received 0 Likes
on
0 Posts
I have never heard anyone say "I cleaned the house today with my low atmospheric pressure cleaning device'.
That's funny.I don't see the analogy between the vented coke can and the vented crankcase. You can't get coke thru sucking a straw in the can if the straw isn't immersed into the coke. After all the pcv valve isn't immersed into the crankcase.That's a given
Wind "pushes from highs to lows. Lows don't "suck" wind in.
This post is the longest bit of nonsense I have ever read. PCV or no PCV......No really big friggin deal...............
04-28-2009, 01:57 PM
#180
Le Mans Master
