Crankcase

	Email		Print
	Bookmark		Link

Crankcase

For the Transformers characters see Crankcase (Transformers).

In an internal combustion engine

Internal combustion engine

The internal combustion engine is an engine in which the combustion of a fuel occurs in a combustion chamber inside and integral to the engine. In an internal combustion engine it is always the expansion of the high temperature and pressure gases that are produced by the combustion which apply force to the movable component of the engine, such as...
, the crankcase is the housing for the crankshaft

Crankshaft

The crankshaft, sometimes casually abbreviated to crank , is the part of an engine which translates reciprocation linear piston motion into rotation....
. The enclosure forms the largest cavity in the engine and is located below the cylinder block

Cylinder block

The cylinder block or engine block is a machined casting containing cylindrically bored holes for the pistons of a multi-cylinder reciprocating internal combustion engine, or for a similarly constructed device such as a pump....
.

Besides protecting the crankshaft and connecting rod

Connecting rod

In a reciprocating piston engine, the connecting rod or conrod connects the piston to the crank or crankshaft. The connecting rod was invented sometime between 1174 and 1200 when a Inventions in medieval Islam, Timeline of Islamic science and engineering and Artisan named al-Jazari built five machines to pump water for the kings of t...
s from foreign objects, the crankcase serves other functions, depending on engine type.

a class="link1" onMouseover='showByLink("m8160437",this)' onMouseout='hide("m8160437")'href="http://www.absoluteastronomy.com/topics/Two-stroke_cycle">two-stroke

Two-stroke cycle

The two-stroke internal combustion engine differs from the more common four-stroke engine by completing the same cycle in only two strokes of the piston, rather than four....
gasoline

Gasoline

File:GasCan.jpgGasoline or petrol is a petroleum-derived liquid mixture, primarily used as fuel in internal combustion engines.It consists mostly of aliphatic hydrocarbons, enhanced with iso-octane or the aromatic hydrocarbons toluene and benzene to increase its octane rating....
engines, the crankcase is sealed and is used as a pressurization chamber for the fuel/air mixture.

Discussion

Ask a question about 'Crankcase'

Start a new discussion about 'Crankcase'

Answer questions from other users

Full Discussion Forum

Encyclopedia

For the Transformers characters see Crankcase (Transformers).

In an internal combustion engine

Internal combustion engine

Crankshaft

Cylinder block

Connecting rod

Two-stroke engines

In two-stroke

Two-stroke cycle

The two-stroke internal combustion engine differs from the more common four-stroke engine by completing the same cycle in only two strokes of the piston, rather than four....
gasoline

Gasoline

Vacuum

A vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty," but in reality, no volume of space can ever be perfectly empty....
in the crankcase which aspirates fuel and air. As the piston travels downward, the fuel/air charge is pushed from the crankcase and into the cylinder.

Unlike four-stroke gasoline engines, the crankcase does not contain engine oil because it handles the fuel/air mixture. Instead, oil is mixed in with the fuel, and the mixture provides lubrication for the cylinder walls, crankshaft and connecting rod

Connecting rod

Four-stroke engines

In a four-stroke

Four-stroke cycle

Today, internal combustion engines in automobile, trucks, motorcycles, aircraft, construction machinery and many others, most commonly use a four-stroke cycle....
engine, the crankcase is filled mainly with air and oil, and is largely sealed off from the fuel/air mixture by the pistons.

Oil circulation

Oil circulation is kept separate from the fuel/air mixture, thereby preserving oil rather than burning it as happens in two-stroke engines. Oil moves from its reservoir, is pressurized by an oil pump

Oil pump

Oil pump may refer to:* A Submersible pump, often used to pump oil out of wells* A Pump jack, often used to pump oil out of wells* An Oil pump , a part of the lubrication system that transports engine oil...
, and is pumped through the oil filter to remove grit. The oil is then squirted into the crankshaft and connecting rod bearings and onto the cylinder walls, and eventually drips off into the bottom of the crankcase. In a wet sump

Wet sump

A wet sump is a lubricating motor oil management design for four-stroke cycle piston internal combustion engines which uses a built-in reservoir for oil, as opposed to an external or secondary reservoir used in a dry sump design....
system, oil remains in a reservoir at the bottom of the crankcase, referred to as the oil pan. In a dry sump

Dry sump

A dry sump is a lubricating oil management method for four-stroke cycle and large two-stroke piston internal combustion engines that uses a secondary external reservoir for oil, as compared to a conventional wet sump system....
system, oil is instead pumped to an external reservoir.

Even in a wet sump system, the crankshaft has minimal contact with the sump oil. Otherwise, the high-speed rotation of the crankshaft would cause the oil to froth, making it difficult for the oil pump to move the oil, which can starve the engine of lubrication. Small amounts of oil may splash onto the crankshaft during rough driving, referred to as windage

Windage

Windage is a force created on an object by friction when there is relative movement between air and the object.There are two possible causes of windage:...
.

In a wet sump system, the main dipstick

Dipstick

A dipstick is one of several devices dipped into a liquid to perform a chemical test or to provide a measure of quantity of the liquid.A "dipstick" can also be a nickname or slang term for someone who is unintelligent and usually ditzy or dislikeable....
and oil filler cap connect to the crankcase.

Air ventilation

During normal operation, a small amount of unburned fuel and exhaust gases escape around the piston ring

Piston ring

A piston ring is an open-ended ring that fits into a groove on the outer diameter of a piston in a reciprocating engine such as an internal combustion engine or steam engine....
s and enter the crankcase, referred to as "blow-by". If these gases remained in the crankcase and condensed, the oil would become more diluted over time, decreasing its ability to lubricate. Condensed water would also cause parts of the engine to rust. To counter this, a crankcase ventilation system exists to draw fresh air in from the air filter

Air filter

An air filter is a device which removes solid particulates such as dust, pollen, mold, and bacterium from the air. Air filters are used in applications where air quality is important, notably in building ventilation systems and in engines, such as internal combustion engines, gas compressors, diving air compressors, gas turbines and oth...
and expel the gases out the PCV valve

PCV valve

The Positive Crankcase Ventilation valve, or PCV valve, is a Check valve that ensures continual evacuation of gases from inside a gasoline internal combustion engine's crankcase....
into the intake manifold. In a non-turbo engine, the intake manifold is at a lower pressure

Manifold vacuum

Manifold vacuum, or engine vacuum in an internal combustion engine is the difference in air pressure between the engine's Manifold and Earth's atmosphere....
than the crankcase, providing the suction to keep the ventilation system going. A turbo

Turbocharger

Check valve

A check valve, clack valve, non-return valve or one-way valve is a mechanical device, a valve, which normally allows fluid to flow through it in only one direction....
somewhere in the tubing to avoid pressurizing the crankcase when the turbo produces boost

Turbocharger

A turbocharger, or turbo, is a gas compressor used for forced induction of an internal combustion engine. Like a supercharger, the purpose of a turbocharger is to increase the mass of air entering the engine to create more power....
.

If an engine is damaged or enters old age, gaps can form between the cylinder walls and pistons, resulting in larger amounts of blow-by than the crankcase ventilation system can handle. The gaps cause power loss, and ultimately mean that the engine needs to be rebuilt or replaced. Symptoms of excessive blow-by include oil being pushed up into the air filter, out the dipstick, or out the PCV valve.

Open crank engine

Early internal combustion engines were of the "open crank" style, that is, there was no enclosed crankcase. The crankshaft, connecting rod, camshaft, gears, governor, etc. were all completely exposed and could be viewed in operation when the engine was running. This made for a messy environment as oil was thrown from the engine and could run on the ground. Another disadvantage was that dirt and dust could get on moving engine parts, causing excessive wear and possible malfunction of the engine. Frequent cleaning of the engine was required to keep it in working order.