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V-8 Engine Operation
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| V-8 Engine Operation |
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| Updated |
Jul 7, 2004 20:29:28 |
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Description:
Below is an overview of a V-8 engine
Cutaway of the V-8 Engine
This diagram shows the flow of fuel and exhaust within a
V8 engine. It shows the timing chain (driven by the crankshaft) drives the
camshaft, which opens the valves. Fuel enters the cylinders via the intake
manifold. The spark-caused explosions force the pistons down. Rotation of
the crank forces the pistons back up, which expels the exhaust.
The Engine's Lubrication System
This animation shows the route taken by the oil within an
engine. The oil pump draws oil from the oil pan, then forces it through
the filter, into the crankshaft passage, through the connecting rods to
the pistons and rings. Oil is pushed through the lifters and pushrods, and
covers the rocker arms. It then flows back down into the pan to complete
the cycle.
The Piston, Rings, and Wrist Pin
The piston converts the potential energy of the fuel,
into the kinetic energy that turns the crankshaft. The piston is a
cylindrical shaped hollow part that moves up and down inside the engine's
cylinder. It has grooves around its perimeter near the top where rings are
placed. The piston fits snugly in the cylinder. The piston rings are used
to ensure a snug "air tight" fit.
The piston requires four strokes (two up and two down) to
do its job. The first is the intake stroke. This is a downward stroke to
fill the cylinder with a fuel and air mixture. The second is an upward
stroke to compress the mixture. Right before the piston reaches its
maximum height in the cylinder, the spark plug fires and ignites the fuel.
This action causes the piston to make its third stroke (downward). The
third stroke is the power stroke; it is this stroke that powers the
engine. On the fourth stroke, the burned gases are sent out through the
exhaust system.
The wrist pin connects the piston to the connecting rod.
The connecting rod comes up through the bottom of the piston. The wrist
pin is inserted into a hole (about half way up) that goes through the side
of the piston, where it is attached to the connecting rod.
Pistons are made of aluminum, because it is light and a
good heat conductor. Pistons perform several functions. Pistons transmit
the driving force of combustion to the crankshaft. This causes the
crankshaft to rotate. The piston also acts as a moveable gas-tight plug
that keeps the combustion in the cylinder. The piston acts as a bearing
for the small end of the connecting-rod. Its toughest job isto get rid of
some of the heat from combustion, and send it elsewhere.
The piston head or "crown" is the top surface against
which the explosive force is exerted. It may be flat, concave, convex or
any one of a great variety of shapes to promote turbulence or help control
combustion. In some, a narrow groove is cut into the piston above the top
ring to serve as a "heat dam" to reduce the amount of heat reaching the
top ring.
Timing Chain/belt
The automobile engine uses a metal timing chain, or a
flexible toothed timing belt to rotate the camshaft. The timing chain/belt
is driven by the crankshaft. The timing chain, or timing belt is used to
"time" the opening and closing of the valves. The camshaft rotates once
for every two rotations of the crankshaft.
The Cylinder Head
The cylinder head is the metal part of the engine that
encloses and covers the cylinders. Bolted on to the top of the block, the
cylinder head contains combustion chambers, water jackets and valves (in
overhead-valve engines). The head gasket seals the passages within the
head-block connection, and seals the cylinders as well.
Henry Ford sold his first production car, a 2-cylinder
Model A, on July 23, 1903.
Push Rods
Push Rods attach the valve lifter to the rocker arm.
Through their centers, oil is pumped to lubricate the valves and rocker
arms.
Flywheel
The flywheel is a fairly large wheel that is connected to
the crankshaft. It provides the momentum to keep the crankshaft turning
without the application of power. It does this by storing some of the
energy generated during the power stroke. Then it uses some of this energy
to drive the crankshaft, connecting rods and pistons during the three idle
strokes of the 4-stroke cycle. This makes for a smooth engine speed. The
flywheel forms one surface of the clutch and is the base for the ring
gear.
Harmonic Balancer (Vibration
Damper)
The harmonic balancer, or vibration damper, is a device
connected to the crankshaft to lessen the torsional vibration. When the
cylinders fire, power gets transmitted through the crankshaft. The front
of the crankshaft takes the brunt of this power, so it often moves before
the rear of the crankshaft. This causes a twisting motion. Then, when the
power is removed from the front, the halfway twisted shaft unwinds and
snaps back in the opposite direction. Although this unwinding process is
quite small, it causes "torsional vibration." To prevent this vibration, a
harmonic balancer is attached to the front part of the crankshaft that's
causing all the trouble. The balancer is made of two pieces connected by
rubber plugs, spring loaded friction discs, or both.
When the power from the cylinder hits the front of the
crankshaft, it tries to twist the heavy part of the damper, but ends up
twisting the rubber or discs connecting the two parts of the damper. The
front of the crank can't speed up as much with the damper attached; the
force is used to twist the rubber and speed up the damper wheel. This
keeps the crankshaft operation calm.
Crankshaft
The crankshaft converts the up and down (reciprocating)
motion of the pistons into a turning (rotary) motion. It provides the
turning motion for the wheels. It works much like the pedals of a bicycle,
converting up-down motion into rotational motion.
The crankshaft is usually either alloy steel or cast
iron. The crankshaft is connected to the pistons by the
connecting-rods.
Some parts of the shaft do not move up and down; they
rotate in the stationary main bearings. These parts are known as journals.
There are usually three journals in a four cylinder engine.
Main Bearings
The crankshaft is held in place by a series of main
bearings. The largest number of main bearings a crankshaft can have is one
more than the number of cylinders, but it can have one less bearing than
the number of cylinders.
Not only do the bearings support the crankshaft, but one
bearing must control the forward-backward movement of the crankshaft. This
bearing rubs against a ground surface of the main journal, and is called
the "thrust bearing."
Connecting Rod
The connecting rod links the piston to the crankshaft.
The upper end has a hole in it for the piston wrist pin and the lower end
(big end) attaches to the crankshaft.
Connecting rods are usually made of alloy steel, although
some are made of aluminum.
Connecting Rod Bearings
Connecting rod bearings are inserts that fit into the
connecting rod's lower end and ride on the journals of the
crankshaft.
Oil Pump
The oil pump is used to force pressurized oil to the
various parts of the engine.
Gear and rotary pumps are the most common types of pumps.
The gear pump consists of a driven spur gear and a driving gear that is
attached to a shaft driven by the camshaft. The two gears are the same
size and fit snugly in the pump body. Oil is carried from the inlet to the
delivery side of the pump by the opposite teeth of both gears. Here it is
forced into the delivery pipe. It can't flow back, because the space
between the meshing gear teeth is too tight.
The rotary pump is driven by the camshaft. The inner
rotor is shaped like a cross with rounded points that fit into the star
shape of the outer rotor. The inner rotor is driven by a shaft turned by
the camshaft. When it turns, its rounded points "walk" around the star
shaped outer rotor and force the oil out to the delivery pipe.
Piston Motion/Bicycle
The pistons in your engine's cylinder are similar to your
legs when you ride a bicycle. Think of your legs as pistons; they go up
and down on the pedals, providing power. The pedals are like the
connecting rods; they are "attached" to your legs. The pedals are attached
to the bicycle crank, which is like the crank shaft, because it turns the
wheels.
To reverse this, the pistons (legs) are attached to the
connecting rods (pedals) which are attached to the crankshaft (bicycle
crank). The power from the combustion in the cylinders powers the piston
to push the connecting rods to turn the crankshaft.
The bicycle played a large part in the process of
inventing the automobile; in fact, in 1896, the first car that Henry Ford
produced was even called a "Quadricycle."
Engine Placement
Mid-engine sports coupes have the engine mounted in front
of the rear axle. Passenger space is limited to two people. Concentrating
the weight in the center of the car improves handling.
The conventional sports coupe's engine is in the front of
the car, driving either the front or rear wheels. This layout reduces
production costs, but luggage space and rear seat room are sacrificed for
the sporty styling.
Vans have engines located in either the front or the
rear. Contemporary sedans have the engine in the front driving the front
or rear axle.
Cylinder
A cylinder is a round hole through the block, bored to
receive a piston. All automobile engines, whether water-cooled or
air-cooled, four cycle or two cycle, have more than one cylinder. These
multiple cylinders are arranged in-line, opposed, or in a V. Engines for
other purposes, such as aviation, are arranged in other assorted
forms.
The first four cylinder engine with a sliding
transmission was in the 1907 Buick.
Oil Seals
Oil seals are rubber and metal composite items. They are
generally mounted at the end of shafts. They are used to keep fluids, such
as oil, transmission fluid, and power steering fluid inside the object
they are sealing. These seals flex to hold a tight fit around the shaft
that comes out of the housing, and don't allow any fluid to pass. Oil
seals are common points of leakage and can usually be replaced fairly
inexpensively. However, the placement of some seals make them very
difficult to access, which makes for a hefty labor charge!
Engine Oil Dip Stick
The engine oil dip stick is a long metal rod that goes
into the oil sump. The purpose of the dip stick is to check how much oil
is in the engine.
The dip stick is held in a tube; the end of the tube
extends into the oil sump. It has measurement markings on it. If you pull
it out, you can see whether you have enough oil, or whether you need more
by the level of oil on the markings.
Oil Filler Cap
The oil filler cap is a plastic or metal cap that covers
an opening into the valve cover. It allows you to add oil when the
dipstick indicates that you need it. Some cars have the crankcase vented
through the filler cap. Oil which is added through the filler passes down
through openings in the head into the oil sump at the bottom of the
engine.
Oil Filter
Oil filters are placed in the engine's oil system to
strain dirt and abrasive materials out of the oil.
The oil filter cannot remove things that dilute the oil,
such as gasoline and acids. Removing the solid material does help cut down
on the possibility of acids forming. Removing the "grit" reduces the wear
on the engine parts.
Modern passenger car engines use the "full flow" type of
oil filters. With this type of filter, all of the oil passes through the
filter before it reaches the engine bearings. If a filter becomes clogged,
a bypass valve allows oil to continue to reach the bearings. The most
common type of oil filter is a cartridge type. Oil filters are disposable;
at prescribed intervals, this filter is removed, replaced and thrown away.
Most states now require that oil filters be drained completely before
disposal, which adds to the cost of an oil change, but helps to reduce
pollution.
Oil Passages
Within the engine is a variety of pathways for oil to be
sent to moving parts. These pathways are designed to deliver the same
pressure of fresh lubricating oil to all parts. If the pathways become
clogged, the affected parts will lock together. This usually destroys
parts that are not lubricated, and often ruins the entire engine.
The oil passages are cleverly drilled into the connecting
parts of the engine, which allows the highly mobile ones (like the
pistons) to have ample lubrication. Originating at the oil pump, they flow
through all of the major components of the engine. In the case of the
pistons and rods, the passages are designed to open each time the holes in
the crankshaft and rods align.
Oil Pan
At the bottom of the crankcase is the container
containing the lifeblood of the engine. Usually constructed of thin steel,
it collects the oil as it flows down from the sides of the crankcase. The
pan is shaped into a deeper section, where the oil pump is located. At the
bottom of the pan is the drain plug, which is used to drain the oil. The
plug is often made with a magnet in it, which collects metal fragments
from the oil.
Serpentine Belts
A recent development is the serpentine belt, so named
because they wind around all of the pulleys driven by the crankshaft
pulley. This design saves space, but if it breaks, everything it drives
comes to a
stop. |
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