good2go

The PCV system is not open to the atmosphere for emissions reasons. Open would be air flowing in and out, it doesn't. It is metered and fed to the intake, not out to the atmosphere. Open would be like in the 60's, with a valve cover breather.

You don't need to reach boiling point to remove contaminants from the oil.

Different LS engines pull timing at different points. The LS7 starts to pull timing at 196. Pull the timing table and see. I would like to see the LS-A table, I'd bet it's similar.

JimmiB

See what you started?

I have been told that it is a trade off, Lower emmisions higher temps, little shorter engine life and a little less performance.

good2go

You're right. There's a chart floating around that isn't very specific but shows performance best in the 180-200 range, and engine life best in the 200-220 range. Above or below that and wear increases and performance decreases.

kenp

iTrader: (9)

Well, the PCV system pulls air in from the intake track and it is OPEN to the atmosphere PERIOD. Vacuum from the engine pulls vapors from the crankcase and the air that replaces those vapors comes from the intake tract , that, once again, is open to the atmosphere. THE INTAKE TRACT IS OPEN TO THE ATMOSPHERE.

System components and operation details

PCV valve on Ford Taunus V4 engine in a Saab 96, between left valve cover and intermediate flange on intake manifold


The PCV valve is only one part of the PCV system, which is essentially a variable and calibrated air leak, whereby the engine returns its crankcase combustion gases. Instead of the gases being vented to the atmosphere, gases are fed back into the intake manifold, to re-enter the combustion chamber as part of a fresh charge of air and fuel. The PCV system is not a classical "vacuum leak". All the air collected by the air cleaner (and metered by the mass air flow sensor, on a fuel injected engine) goes through the intake manifold. The PCV system just diverts a small percentage of this air via the breather to the crankcase before allowing it to be drawn back in to the intake tract again. It is an "open system" in that fresh exterior air is continuously used to flush contaminants from the crankcase and into the combustion chamber.
The system relies on the fact that, while the engine is running under light load and moderate throttle opening, the intake manifold's air pressure is always less than crankcase air pressure. The lower pressure of the intake manifold draws air towards it, pulling air from the breather through the crankcase (where it dilutes and mixes with combustion gases), through the PCV valve, and into the intake manifold.
The PCV system usually consists of the breather tube and the PCV valve. The breather tube connects the crankcase to a clean source of fresh air—the air cleaner body. Usually, clean air from the air cleaner flows into this tube and into the engine after passing through a screen, baffle, or other simple system to arrest a flame front, to prevent a potentially explosive atmosphere within the engine crank case from being ignited from a back-fire in to the intake manifold. The baffle, filter, or screen also traps oil mist, and keeps it inside the engine.
Once inside the engine, the air circulates around the interior of the engine, picking up and clearing away combustion byproduct gases, including a large amount of water vapor which includes dissolved chemical combustion byproducts, then exits through another simple baffle, screen, or mesh to trap oil droplets before being drawn out through the PCV valve, and into the intake manifold. On some PCV systems, this oil baffling takes place in a discrete replaceable part called the oil separator......

No, you don't have to get water in the crankcase to 212* to remove it from the oil, but a higher temperature is clearly more effective. This is probably the best analysis of removing water from the crankcase from a post @ BITOG: Any fluid, water included, will maintain an equilibrium of liquid and gas in an enclosed and only partially filled space. The pressure of the vapour over the liquid is determined by the temperature of the system, and it's a constant at a constant temperature. If you remove vapour from the system, liquid will evaporate to compensate for the loss until the previous pressure is restored. That's how the PCV system gets water out of your motor oil without boiling it out.

Of course, when such a closed system is raised to the "boiling point" of the liquid, the liquid absorbs heat and converts to vapour until all the liquid is gone. This is "boiling off" the liquid.

To clean the water out of your engine oil without boiling, you just have to keep removing the water vapour from the space above the liquid (ie - the enclosed crankcase volume), and the water in the oil will continue to evaporate in an effort to re-establish it's equilibrium vapour pressure.

If your oil is at 200 degrees (F), the vapour pressure of water is relatively high, and your PCV system will draw the vapour out of the engine very efficiently until all that's left is a tiny amount of water vapour inside the crancase. That moisture will condense into the oil as the engine cools, but it will be a negligible amount.

There are two reasons you get creamy oil when running a cold engine:

1 - more water vapour condenses inside the cylinders in the first place (instead of being expelled) because the mass of the engine itself is cold. This means there is more input of water to the oil.

2 - the whole system is cool, so the vapour pressure of the water in the crankcase is quite low, so the PCV system can't extract it. The water's happy being a liquid and riding around in the oil, and until it feels the call of warmer temperatures, it has no inclination to try to support a higher vapour pressure.

Here's info from an oil cooler company - They don't open until oil is 180* for a reason:

THERMOSTATS

MOXXX thermostats are designed to prevent engine oil from flowing through the oil cooler until the desired temperature is reached. Prolonged use of engines in conditions that oil cannot reach optimum working temperatures will cause sludge formation and crankcase oil dilution, leading to excessive wear especially in the cylinder bores. Thermostats combat this by regulating oil flow to accelerate warm up. This in turn reduces drag, helping to yield optimum engine efficiency and performance. The proven design and reliability of the MOXXX thermostat make them the choice of automotive and marine racing teams world wide. They are also well suited for aviation applications.
MOXXX thermostats are available two styles. The OTI version utilizes push-on hose barbs and is available for either 3/8" or 112" i.d. hose. 0T2 type thermostat is designed with thread-on male fittings available in all popular JIC/-AN sizes (-8AN, -lOAN, -12N, -I6AN) and BSP sizes (1/2", 5/8"). For additional plumbing versatility a 1/2" female thread OT2 version is available which will allow any male/male union to be installed.

0T1 Specifications

0T2 Specifications

• All Aluminum CNC machined housing
• Push-on hose barb 3/8", 1/2" O.D.
• Lightweight (8oz)
• Factory set 180 degree operation
• Includes mounting bracket

• All aluminum CNC machined housing
• Aeroquip compatible male fittings AN-8, AN-10, AN-l2and AN-16
• Lightweight (16 Oz.)
• Factory set 180 degree operation
  (optional temperatures ranges available)
• Includes mounting bracket

So, run the 160* thermostat in your daily driver with the knowledge that you are not optimising the combustion characteristics of the fuel or the capability of your PCV system to remove water from your oil.

safemode

iTrader: (1)

I think people are confusing metered air with not being open to the atmosphere. It definitely is, it's just measured. So when the car is off, this air is moving back and forth and the fact that it's measured doesn't matter cuz the car is off.

Metered doesn't mean there is some magical one way valve that blocks the air now. Even the TB can't stop air from freely moving around the oil because the PCV is in front of the TB. (not that the TB is air tight either.)

good2go

Hey Ken: I agree with you completely on how a modern PCV system works, I just don't want it confused with the old open systems of decades ago. If people think that they can just put a breather on the valve cover with or without rerouting the PCV lines they will be disabling the system and without the vacuum pulling air through the crankcase their oil will stay contaminated and need to be changed very often, or they are causing a vacuum leak to affect their A/F.

As for the oil thermostats, they are a bad idea for LS engines. They are a restriction to oil flow and can cause our bypass valves to open, meaning no oil flow to the filter. Not good.

As for the 160, it's still a good mod. My oil and coolant get up to temps high enough for proper operation and not hot enough to cause knock.