What are the benefits of crankcase ventilation systems?
An added benefit of many crankcase ventilation systems is the addition of an air filter vacuum monitor, which alerts the operator to the need for element replacement. Such filter monitors can be added to many air filter housings, even those that don’t benefit from after-market crankcase ventilation systems.
How does a crankcase ventilation hose work?
This type of crankcase ventilation hose usually snakes down the side of an engine to the bilge where it ideally emits just a small amount of gas, oil and water vapor. This crankcase ventilation system installation represents good intentions with poor execution.
Do two-strokes need a crankcase ventilation system?
Two-stroke engines with a crankcase compression design do not need a crankcase ventilation system, because normal operation of the engine involves sending the crankcase gases to the combustion chamber.
Can I add a vent to the crankcase?
Some owners choose to add overly large ports to the crankcase and valve cover and just vent to the atmosphere. If the venting ports are large enough, and there are enough of them, it has been found to do the job adequately. Understand that this is not considered emissions legal as you will be exhausting un-burnt oil vapors into the air.
What is a crankcase ventilation system?
A crankcase ventilation system removes unwanted gases from the crankcase of an internal combustion engine. The system usually consists of a tube, a one-way valve and a vacuum source (such as the intake manifold).
Why do engines use positive crankcase ventilation?
Positive crankcase ventilation (PCV) systems— first used in the 1960s and present on most modern engines— send the crankcase gases back to the combustion chamber, in order to reduce air pollution. Two-stroke engines with a crankcase compression design do not need a crankcase ventilation system, because normal operation of ...
How does an intake manifold vacuum work?
Intake manifold vacuum is applied to the crankcase via the PCV valve. The airflow through the crankcase and engine interior sweeps away combustion byproduct gases. This mixture of air and crankcase gases then exits, often via another simple baffle, screen, or mesh to exclude oil droplets, 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'. Aftermarket products sold to add an external oil baffling system to vehicles, which were not originally installed with them, are commonly known as " oil catch tanks ".
How does a PCV system work?
In order for the PCV system to sweep fumes out of the crankcase, the crankcase must have a source of fresh air. The source of this fresh air is the "crankcase breather", which is usually ducted from the engine's intake manifold. The breather is usually provided with baffles and filters to prevent oil mist and vapour from fouling the air filter.
What was the first refinement in crankcase ventilation?
The first refinement in crankcase ventilation was the road draught tube.
Why is carbon build up in intake manifold?
Carbon build-up in the intake manifold may occur when blow-by gases are allowed to permanently contaminate the intake air because of a failing PCV system. Carbon build-up from blow-by gases on intake valves are usually not a problem in port injected engines.
What caused the draught tube to become clogged with snow?
The draught tube could become clogged with snow or ice, in which case crankcase pressure would build and cause oil leaks and gasket failure.
Where does open crankcase venting go?
In some cases and even recently it was simply vented to the atmosphere, known as open crankcase ventilation, which, on a boat means into the engine room. This type of crankcase ventilation hose usually snakes down the side of an engine to the bilge where it ideally emits just a small amount of gas, oil and water vapor.
What is the gas that passes through the crankcase?
Collectively, blow by includes soot or particulate matter, water vapor, unburned fuel and exhaust byproducts such as carbon dioxide, carbon monoxide and nitrogen oxides to name a few.
What is the blue hose on a crankcase?
The blue hose at the bottom drains coalesced oil back to the oil pan. This air filter, part of an aftermarket crankcase ventilation system, is saturated with oil and long overdue for service, and the same is likely true of the engine it serves as well.
What is the purpose of the lower rings on a piston?
The upper two rings contain the cylinder’s compression, the lower rings, with the spring-like device, are designed to remove oil from the cylinder wall on the piston’s downward stroke.
Do engines need a closed crankcase?
Although it’s not a necessity per se , most engines and engine rooms both old and new will benefit from the installation of a proprietary closed crankcase ventilation system and many engine manufacturers now include off the shelf brands as standard equipment.
Is a crankcase ventilation system effective?
As valuable as they are , after-market crankcase ventilation systems are only effective when properly installed. This one isn’t, its outboard end droops down, preventing oil from draining properly. The quality and effectiveness of crankcase ventilation systems ranges from primitive, the hose leading into the bilge, to sophisticated, serviceable, ...
How does PCV work?
The fumes and vapor are drawn into the combustion chamber and burned away. The PCV system keeps the inside of the engine clean. It also releases pressure without causing a leak. The fumes and vapors are burned away, which improves emissions.
What is a PCV engine?
However, they all contributed to smog and pollution. Most modern engines use a Positive Crankcase Ventilation (PCV) system. The system is fairly simple: A filtered air source serves as an inlet. This could be a Valve Cover Breather or, A hose connected to the air intake tube.
When was positive crankshaft ventilation invented?
Then, in the early 1960s, positive crankshaft ventilation (PCV) was invented. This is now considered the beginning of automobile emission control. Positive crankcase ventilation involves recycling these gases through a valve (called, appropriately, the PCV valve) to the intake manifold, where they're pumped back into the cylinders ...
What is the term for the gas that escapes from a crankcase?
This escaping gas is called blow-by and it's unavoidable.
What is a PCV valve?
A Positive Crankcase Ventilation (PCV) system regulates the vacuum pull through its crankcase. Once the vacuum gets higher than desired at idle, the PCV valve shuts off and stops that vacuum. The drop in vacuum leads to an increase in RPM, which in turn allows more gas to be pulled in.
How much does a PCV valve cost?
The average cost of a PCV valve depends entirely on the type of failure. If the valve needs to be replaced completely, it can set you back $65 to $83 without labor. Car manufacturers suggest that individuals keep on getting their PCV valves replaced regularly.
What happens if a PCV valve is overused?
If PCV valves get damaged or overused, it can lead to engine oil contamination, sludge build-up, oil leaks, high fuel consumption and a number of other engine-related problems. This might lead to an irrevocably damaged engine.
How do oil and air filters work?
Alternatively, the air and oil filter may require the recycled gases to go down a tube with holes in its side. The lighter air molecules escape through the holes, while the heavier oil droplets fall all the way to the bottom, where they can be removed.
Why is it not desirable to have gas in a cylinder?
It isn't always desirable to have these gases in the cylinders because they tend to be mostly air and can make the gas-air mixture in the cylinders a little too lean -- that is , too low on gasoline -- for effective combustion.
Overview
A crankcase ventilation system removes unwanted gases from the crankcase of an internal combustion engine. The system usually consists of a tube, a one-way valve and a vacuum source (such as the intake manifold).
The unwanted gases, called "blow-by", are gases from the combustion chamber which have leaked past the piston rings. Early engines released these gases t…
Source of crankcase gases
Blow-by, as it is often called, is the result of combustion material from the combustion chamber "blowing" past the piston rings and into the crankcase. These blow-by gases, if not ventilated, inevitably condense and combine with the oil vapour present in the crankcase, forming sludge or causing the oil to become diluted with unburnt fuel. Excessive crankcase pressure can furthermore lead to engine oil leaks past the crankshaft seals and other engine seals and gasket…
Atmospheric venting
Until the early 20th century, blow-by gases escaped from the crankcase by leaking through seals and gaskets. It was considered normal for oil to leak from an engine and drip onto the ground, as this had also been the case for steam engines in the decades before. Gaskets and shaft seals were intended to limit the leakage of oil, but they were usually not expected to entirely prevent it. The blow-by gases would diffuse through the oil and then leak through the seals and gaskets into th…
Positive crankcase ventilation (PCV)
Although the modern purpose of a positive crankcase ventilation (PCV) system is to reduce air pollution, the original purpose was to allow an engine to operate underwater without the water leaking in. The first PCV systems were built during World War II, to allow tank engines to operate during deep fording operations, where the normal draught tube ventilator would have allowed water to enter th…
Alternatives
Two-stroke engines which use crankcase compression do not require a crankcase ventilation system, since all of the gases within the crankcase are then fed into the combustion chamber.
Many small four-stroke engines such as lawn mower engines and electricity generators simply use a draught tube connected to the intake system. The draught tube routes all blow-by gases back into the intake mixture and is usually located between the air filter and carburetor.