Why Do NA Cars Even Have PCV Valves?

[williaty]

Originally Posted by steven765

agreed thats why i am planning on connecting the drain to the valve cover, in theory it (the drain) will then see vac at low idle. similar to what the guy did over on the rs forums.

It's not going to work the way you think it is. The pressure gradient isn't going to be large enough.

But, if you feel like wasting your time and money, don't let me get in your way.

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[steven765]

Easy killer, it was meant as a question. I'm trying to understand why it would not work and have a discussion.

I'm basing it of of this link where a guy fitted up a crawford and it did work for him.
http://www.rs25.com/forums/f5/t89360...ck-airbox.html

I am however still trying to wrap my head around everything so better feedback is more then welcome. Why wouldn't the pressure gradient be high enough, the return prevents it from drawing through it? My thought would then be a one way check on the valve line forcing it to draw back form the drain so it has a higher gradient.

[williaty]

He and I PMed back and forth A LOT during the time not long after that thread was initially posted. The final outcome of the conversation, when compared to the first post of this thread, is that he's effectively broken the PCV system and it's no longer functioning as designed. In other words, he's reducing his oil loss because he's effectively disabling the PCV system under most conditions. It'll release pressure when the crankcase goes positive, but that's it.


If you read his more recent posts, you'll see he's basically had to redesign the AOS from the ground up to try to get it to behave properly. He's basically tried to achieve what I was saying was required in the latter half of this thread.

BTW, my solution to reduce/stop blow-by was to rebuild the engine and break it in properly (aka not even a little bit like Subaru wants you to). I've had zero oil consumption in the last 20k miles.

[steven765]

Yea I was posting over there his latest modification to the system seems to have worked. He reinstalled the pcv, and is draining back into the valve cover not the pcv. Had you talked with him about the newer mods?

So with my new ccr engine, how would you recommend breaking it in? When the car was new I just took it easy, no cruise the first 1000, changed oil, then dino oil to 3k, then switched to synthetic.

[williaty]

First of all, you MUST have an oil temp gauge. That's not optional.

First start, idle it to be able to burp the coolant and to get some heat into the coolant. Then drive it VERY VERY gently to get the oil up to temp. Then do 2kRPM to redline full throttle pulls followed by coasting down in gear from redline back to 2kRPM. Repeat for 20mi, making sure you never overheat the oil. Change the oil. You engine is now 80% broken in. Go back out after the oil change, drive it VERY VERY gently until the oil is up to temp, then do as much WOT/coast down as you can for the next 200mi, making sure the oil doesn't overheat. Change the oil. You're done.

[steven765]

hmm where did you tap into the block for oil temp? I'd been thinking about that.

[williaty]

Originally Posted by steven765

hmm where did you tap into the block for oil temp? I'd been thinking about that.

My opinion is that the correct location is the plug on the top of the block at the front of the oil gallery. Basically, take out the stock oil pressure switch, put it somewhere else, and stuff the temp sender in there.

[vristang]

I'm new here, but I've had to mess with crankcase evacuation on my Mustangs...
I have an '01 Outback H6, and came here looking for head info, but thought I could offer some input on this subject...

Originally Posted by LetItSnow

Re: AOS

Anybody who wants to dump this junk (the contents of my two catch cans, albeit supercharged) back into their crankcase over and over is more than welcome to, but I sure wouldn't.

I agree...
On my 2.3 commuter mustang I installed an open breather system, using a catch can/separator from Moroso.
Eventually I will hook up an electric pump, but haven't had a chance to wire it in yet...

The 2.3 car has one vent from the crankcase and one from the valve cover... the more vents the better.

The crap that comes out of the crankcase is all waste product, and dumping it back into the crankcase will only reduce the effective life of the additives in your oil.
For the same reason, I don't want the stock pcv system dumping those waste products into the intake charge... the only reason to do so, is to meet emissions test requirements.

I'm currently doing head gaskets in my H6, and the crankcase vent system will be revised in the process. Not exactly sure how just yet, but the pcv will be eliminated so that I don't get any oil vapor in the intake charge.

[williaty]

The crap in the PCV system is NOT all waste product. It's water, which is everywhere in your engine anyway (hence needing to drive it out via run times longer than a 5 minute commute). It's oil, which, you know, is a necessary thing. It's soot, which is also everywhere in your engine. On an engine that we'd consider perfect with very little blow-by all this same stuff would be swimming around in there but you wouldn't see it. The only difference is that, when ring sealing drops off, this stuff actually comes out of the engine to a place where we can see it and then you guys obsess over it. So long as the oil doesn't end up in the combustion chamber, nothing else is doing any harm.

You guys fussing about this stuff are like some rich woman worrying about a scuff on her Prada shoes.

[colorfull]

Originally Posted by williaty

So long as the oil doesn't end up in the combustion chamber, nothing else is doing any harm.

You guys fussing about this stuff are like some rich woman worrying about a scuff on her Prada shoes.

LOL, very true...

My observations on my 120K km engine is that most of the oil that gets in the intake comes from the PCV, the main reason being that it is directly connected to the intake manifold where the vaccuum differential is bigger.
The head covers vent connect to the torque box and the pressure differential between the 2 varies from positive to negative depending on the throttle position, and also because there nothing to act as a one way valve.

Since my goal is to stop oil from getting in the the combustion chamber, I plan on installing 2 catch cans, one for the PCV hose, and one that will connect to the 2 cover vents.
I will then have to empty those 2 cans everytime I change the oil on my car, since my understanding is that there is no functional way to automatically emply them in the engine case without breaking the way the PCV system is designed.

Anything wrong in my train of thought?


BTW I can vouch for Williaty's break-in method as I used a very similar method to break-in my motorcycle engine with great success. I also saw the internals of 4 stroke motorcycle engines that were broken in with the traditional method vs the one explained by Will, and now I wish I knew about this when I first bought my car.

[williaty]

Originally Posted by colorfull

I will then have to empty those 2 cans everytime I change the oil on my car, since my understanding is that there is no functional way to automatically emply them in the engine case without breaking the way the PCV system is designed.

That's how I ran for a long time on my old engine. Got to be a PITA to empty the can often enough. Only the one on the PCV to IM line ever had any oil in it. The valvecover cans were always bone dry.

My thought now on using an AOS and not breaking the PCV system is that maybe it needs an electronic valve that'll detect engine shut off and open the valve, then close it again when the engine turns back on.

[vristang]

What is this aos system?

Does it drain catch can contents back into the crankcase?

[williaty]

Originally Posted by vristang

What is this aos system?

Does it drain catch can contents back into the crankcase?

Yeah, it's just a catch can that empties itself.

[vristang]

I have to ask why???

Why dump that stuff back into the crankcase?

[williaty]

Originally Posted by vristang

I have to ask why???

Why dump that stuff back into the crankcase?

Because there's nothing in it that's harmful that's not in all your oil anyway. By recircing it, you no longer have to constantly add oil to the car.

[vristang]

How does the moisture get out?

[williaty]

Through the PCV system and into the intake just like normal. At operating temperatures, the water vapor will not condense out into the AOS, unlike the oil. The water found in catch cans and AOSes that get plugged up is only from periods when the system is below operating temperature. In other words, it condenses after you turn the car off as the whole thing cools down. When you get the car fully warmed up next time, it evaporates and makes its way out. This is exactly the same behavior as with a non-AOSed car.

[vristang]

Got a link that describes this AOS system?

[vristang]

Air oil separator...

I need to look at your diagrams of this setup again...

I still emphatically disagree with continually dumping waste products back into crankcase though...

[williaty]

Originally Posted by vristang

I still emphatically disagree with continually dumping waste products back into crankcase though...

In that case, your current oiling setup fails you epically.

To prevent the contamination of the oil by combustion byproducts, first, you'll need to buy a huge trailer.

Then you'll need to buy two multi-hundred-gallon tanks to put on the trailer.

Fill one tank with new oil. It should only cost you a few thousand dollars per fill.

Plumb the intake side of the oil pump into the full tank.

Put a dry-sump pan and pump under the engine and plumb the output to the empty tank.

Now, as you drive, fresh oil will continuously be drawn into the engine and the contaminated oil will constantly be removed into the waste oil tank.

If you get 500-gallon tanks, you'll only have to stop and buy new oil every 30 miles or so.





Seriously, if you're not doing that, stop whining about the combustion byproducts in the vapors in the PCV system. They're in the oil no matter what unless you're constantly using virgin oil. The only difference is that you can see them in a catch can so you can obsess about them. Without the catch can, they're still in your oil, you're just not worried about them.

[vristang]

No need to step into the ridiculous...

The advantage of the catch can type separator isn't that I can obsess over the oil... But rather that I can filter that crap out of the engine without contaminating my intake charge.

[williaty]

Originally Posted by vristang

No need to step into the ridiculous...

The advantage of the catch can type separator isn't that I can obsess over the oil... But rather that I can filter that crap out of the engine without contaminating my intake charge.

The "crap" is still in your engine. The AOS keeps the oil out of your intake charge. That's the most important thing a catch can or an AOS does. The other contents of the PCV system vapor are water and a little bit of combustion byproducts. The water is in there anywhere. There's absolutely nothing you can do about it. The fact that your engine 1) changes temperature and 2) reacts hydrocarbons with oxygen leads inevitably to the fact that there's going to be water in your engine oil. When the engine warms up, the water vaporizes and makes its out the PCV system and into the cylinders. This is exactly what you want to have happen and it happens no matter if you're stock, have a catch can, or have an AOS. The only way to deal with it is to get the engine warm and keep it warm long enough to drive the water out of the oil. BTW, this exact same problem happens with gasoline getting into the oil and the same thing is the only fix: warm the engine up and keep it warm. The combustion byproducts as well are getting into your oil. If you look at a schematic of the EJ-series engine, you'll notice that the oiling return system shares space with the PCV system and crankcase volume. In other words, that blow by that contains the combustion byproducts is being blown directly into suspension in the oil every bit as much as it's being blown out the PCV system.

So, be specific, what's your problem? There's oil in the system, which obviously is ok to be there. There's water in the system, which obviously is ok to be there. There's combustion byproducts in the system that are unavoidable.

Be specific as to what you're objecting to and cite SAE publications showing it's actually a problem.

[vristang]

Your getting cranky, and argumentative and it isn't really needed...

I think I still lack a clear vision of what you define as 'AOS'.
A diagram/schematic of exactly the system you are proposing would be nice.

As far as exactly what my problem is...
As best I can interpret, your AOS system recycles combustion byproducts back into the crankcase.
You seem to be saying that since it came from the crankcase, it must be ok.
I'm saying that all of those byproducts are harmful to the longevity of the oil... which is part of why PCV systems exist in the first place.


Nice that you place burden of proof on me. LOL It is your theory isn't it?
I am an SAE member, and have access to a lot of SAE papers/specs through work. Maybe I will look some stuff up, depending on time constraints... But please provide a diagram of the system as you are describing it (pcv/aos).

[williaty]

Originally Posted by vristang

Your getting cranky, and argumentative and it isn't really needed...

I think I still lack a clear vision of what you define as 'AOS'.
A diagram/schematic of exactly the system you are proposing would be nice.

As far as exactly what my problem is...
As best I can interpret, your AOS system recycles combustion byproducts back into the crankcase.
You seem to be saying that since it came from the crankcase, it must be ok.
I'm saying that all of those byproducts are harmful to the longevity of the oil... which is part of why PCV systems exist in the first place.


Nice that you place burden of proof on me. LOL It is your theory isn't it?
I am an SAE member, and have access to a lot of SAE papers/specs through work. Maybe I will look some stuff up, depending on time constraints... But please provide a diagram of the system as you are describing it (pcv/aos).

Getting? I've been cranky on this forum for pushing a decade!

An AOS is not my pet idea. There are a number of off-the-shelf commercial designs that you can study at your leisure.

I'm saying I have seen no documented evidence that a system that returns the coalesced liquids to the oiling system harms the system. You're claiming that they do. I can't prove the non-existence of research supporting your claim. You can prove research supporting your claim exists solely by producing said research. Yes, the burden of proof is on you.

[vristang]

Abstract from one paper...

SAE 240032
http://papers.sae.org/240032

Abstract:

It is generally recognized that the dilution of crankcase-oil with water and unburned fuel tends to accelerate the wear of engine bearings, cylinders and pistons. The author traces the engineering development of a rectifying device and system designed to combat this problem. In this system, diluted oil that tends to work-up past the pistons, in company with the water vapor and unburned fuel that tend to work down into the crankcase, is drawn from the cylinder-walls and pistons by vacuum. This diluted oil is conducted into a still or rectifier where it is subjected to heat from the engine exhaust. The heating action is just sufficient to volatilize the fuel and water, the resulting vapor being returned to the intake-manifold and thence to the engine where it is burned. The lubricating oil that remains behind is conducted back into the crankcase. The system functions automatically. A float-actuated mechanism controls the flow of the diluted oil through the rectifier, and a thermostatically-controlled valve regulates the degree of heat to which the liquid is subjected.

Your AOS system isn't filtering out any of the fuel or water contaminants, is it?


The point is that all of the things that vent from the crankcase, with the only exception of oil fumes, are waste products. These things are not there because the lubrication engineers wanted them there. In fact the lubrication engineers specifically add products to the oil to combat the presence of these waste products.
By continually dumping the waste products back into the crankcase, you will sooner 'use up' all of the oil additives... which will result in decreased oil performance.

Why would one knowingly do that?

Spent about 15 minutes working with google and found these...



Another source:
http://www.synpsg.com/Oil_Sludge_Problem.html

Sludge is the thickening and breakdown of the oil as it deteriorates, and as moisture and contaminants build up

A news article:
http://www.utsandiego.com/uniontrib/...14sludge2.html

What causes sludge?

AUTOWEEK

May 14, 2005

Industry experts say some modern engines are more prone to sludge than older engines. Here are the top four reasons.

1. Engine breathing: Oil vapor and combustion gases that develop inside an engine must be purged, usually by burning in the cylinders. If the gases and oil vapor are not disposed of, sludge can form.

Toyota will not say what causes sludge in some of its V-6 and four-cylinder engines, but after the problem emerged, the company changed the baffles under the valve cover, part of the engine's breathing system.

From bobistheoilguy...
http://www.bobistheoilguy.com/what-is-blow-by/

When the fuel, air and moisture slip into the crankcase they contaminate and dilute the oil in the crankcase.

Among the many gasses in your compression chamber are unburned fuel, moisture, sulfur dioxide and soot. Once these gasses slip into your crankcase they can dilute into your engine causing great damage.

The detergents and Molybdenum Disulfide work together to clean the soot and deposits off of your rings allowing them to better seal the combustion chamber.

bobistheoilguy again...
http://www.bobistheoilguy.com/forums...&Number=530105

Yes aeration is the last one.

so the given answer is. High temperatures,presence of contaminants such as water, presence of copper or other catalytic metals, aeration, additive depletionn, mixed lubricants.