Charles and Frank Duryea designed and built
the car together, showing off their invention on the streets of
Springfield, Massachusetts, on September 22, 1893. See more Automobile
the hoods of our cars can be a mysterious, confusing jumble of
metal, tubes and wires to the inexperienced.
start when we turn the key in the ignition which triggers a complex
sequence of events that gets our car moving and take us where we want
the battery completes an electrical circuit, and that activates the
electronic control unit, the fuel pump, and the fuel injectors. At
the same time - next power flows from the battery to the starter,
which cranks the engine. The starter turns the crankshaft, the
driving force of the whole engine, and it is kept turning by the
pistons, which are like the pedals on a bicycle.
performed by the heart of the automobile,
converts fuel into the energy that powers the automobile.
operate, it requires clean air for the fuel, water for cooling,
electricity (which it generates) for igniting the fuel, and
oil for lubrication.
battery and electric starter get it going.
is an Engine
engine is a machine that converts energy into mechanical work.
engine may get its energy from any of a number of sources, including
fuels, steam, and air or water under pressure.
engine is an engine which burns its fuel outside of the engine as a
steam engine does.
Internal Combustion Engine
is any type of machine that obtains mechanical energy directly from
the expenditure of the chemical energy of fuel burned in a combustion
chamber that is an integral part of the engine.
principal types of internal-combustion engines are in general use:
the diesel engine,
and the gas turbine.
Otto-cycle engine, named after its inventor, the German technician Nicolaus
Otto in 1876
, is the familiar gasoline engine used in automobiles today because
its efficient, relatively inexpensive and easy to refuel. ;
diesel engine, named after the French-born German engineer Rudolf
Christian Karl Diesel, operates
on a different principle and usually uses oil as a fuel. It is
employed in electric-generating and marine-power plants, in trucks
and buses, and in some automobiles.
Otto-cycle and diesel engines are manufactured in two-stroke
purpose of a gasoline car engine is to convert gasoline into motion
so that your car can move.
the easiest way to create motion from gasoline is to burn the
gasoline inside an engine.
a car engine is an internal combustion engine
combustion takes place internally. (explosion
the automobile engine is an "internal" combustion engine,
a container must be found to keep the explosion on the inside,
would be the combustion
consists of a Cylinder.
of it like this!
the gasoline in a sturdy metal can and press down a tight-fitting lid.
a way to introduce a lighted match inside that can, and bam!
nearly contained. The lid will blow off.
the engine isn't perfect just yet, but the "metal can"
idea is an example of how an automobile cylinder works.
of a can with the lid sealing the opening from the outside,
cylinder is a "can" constructed of thick and sturdy
alloys, with the lid sealing the mouth of the cylinder from the
inside, like the lid on a soup can.
way, when the gasoline explodes (the
provides the match-like spark),
lid moves straight up in the identical line of motion every time.
good example would be an old war cannon, where
the soldiers load the cannon with gun powder and a cannon ball and
light it. That
is internal combustion.
combustion gasoline engines run on a mixture of gasoline and air.
The ideal mixture is 14.7 parts of air to one part of gasoline (by
weight.) Since gas weighs much
more than air, we are talking about a whole lot of air and a tiny bit
of gas. One part of gas that is completely vaporized into 14.7
parts of air can produce tremendous power when ignited inside an engine.
problems must be solved to make our engine work.
the explosion, the exhaust must be siphoned off and a new supply of
fuel must be introduced.
all, one explosion won't propel a car very far.
the top of the cylinder is a pair of valves. (Okay, so many modern engines
have tweaked this basic arrangement by adding additional valves, but the principle is still the same.)
valve that lets the fuel in is called the "intake" valve.
one that lets out the exhaust, the
by-product of the explosion,
called the "exhaust" valve.
cylinder and its valves manipulate pressure in two ways that
are no more sophisticated than what a small child at play might do.
Have you ever sucked on the end of a Coke bottle until
all the air inside was gone and your lips were pulled into the opening?
All at once, a small leak developed and a tiny stream
of air would rush in, making a squeaky noise and tickling your lips.
What you did by drawing all the air out of the
bottle was to create a vacuum. When the small leak around your lips
inevitably developed, it wasn't the empty bottle drawing air back in,
it was the normal pressure of the air around us (15 pounds per
square inch) pushing its way back in.
And every child at some time discovers the joys of
blowing up a balloon and releasing it with the end untied.
Did you ever leave a covered pot of cooking rice or
spaghetti unattended? As the water heats up, gases or steam build and
expand, creating pressure and eventually pushing the top off.
In cars there is a great deal more pressure, and only
an airtight engine and cylinders can trap this pressure for its
The compressed air forces its way out of the opening,
the area of least resistance. Part of the genius of the four-stroke
engine is its use of pressure and vacuum. Pressure and vacuum are
keys to the success of the engine's four strokes: intake,
compression, firing (power), and exhaust.
the second problem,
problem of a different sort:
explosion sends energy in a linear (related
to a straight line)motion,
tires spin around.
restate the tire problem the way Henry
Ford might have said it:
and down motion)
energy produced by the gasoline explosion has to be converted into
and round motion) energy.
the cylinder, usually fixed, that is closed at one end and in which
a close-fitting piston slides.
are the main factor in carrying out this task as they move
and forth within the cylinder
is called reciprocating).
in-and-out motion of the piston varies the volume of the chamber
between the inner face of the piston and the closed end of the cylinder.
end of the crankshaft
is a gear and on the other end a heavy flywheel
with counterweights, which by their inertia minimize irregularity in
the motion of the shaft.
That gear meshes with a
gear on another shaft called a camshaft.
On the camshaft and
beneath each valve is a teardrop-shaped cam lobe.
The piston turns (powers)
the crankshaft with every firing stroke transforming
the reciprocating motion of the piston into rotary motion.
multicylindered engines the crankshaft has one offset portion, called
a crankpin, for each connecting rod, so that the power from each
cylinder is applied to the crankshaft at the appropriate point in its rotation.
The crankshaft not
only powers the car, it also powers the camshaft.
And the cam lobes,
positioned above each valve, push the valves open each time the
camshaft rotates and the cam lobe touches the valve stem.
The proper alignment of the
gears keeps the engine firing to provide maximum power.
The fuel supply system of
an internal-combustion engine consists of a tank,
a fuel pump,
and a device for vaporizing or atomizing the liquid fuel.
In Otto-cycle engines this
device is either a carburetor or,
In most engines with a
carburetor, vaporized fuel is conveyed to the cylinders through a
branched pipe called the intake
manifold and, in many engines, a similar exhaust
manifold is provided to carry off the gases produced
by combustion. The fuel is admitted to each cylinder and the waste
gases exhausted through mechanically operated poppet
valves or sleeve
valves. The valves are normally held closed by the
pressure of springs and are opened at the proper time during the
operating cycle by cams
on a rotating camshaft that is geared to the crankshaft.
By the 1980s more
sophisticated fuel-injection systems, also used in diesel engines,
had largely replaced this traditional method of supplying the proper
mix of air and fuel. In engines with fuel injection, a mechanically
or electronically controlled monitoring system injects the
appropriate amount of gas directly into the cylinder or intake
valve at the appropriate time. The gas vaporizes as
it enters the cylinder. This system is more fuel efficient than the
carburetor and produces less pollution.
In all engines some means
of igniting the fuel in the cylinder must be provided.
For example, the ignition
system of Otto-cycle engines described below
consists of a source of low-voltage, direct-current electricity that
is connected to the primary of a transformer
called an ignition coil.
The current is interrupted
many times a second by an automatic switch called the timer. The
pulsations of the current in the primary
induce a pulsating, high-voltage current in the secondary.
The high-voltage current is led to each cylinder in turn by a rotary
switch called the distributor.
The actual ignition device
is the spark plug,
an insulated conductor set in the wall or top of each cylinder. At
the inner end of the spark plug is a small gap between two wires. The
high-voltage current arcs across this gap, yielding the spark that
ignites the fuel mixture in the cylinder.
Because of the heat of
combustion, all engines must be equipped with some type of cooling
system. Some automobile engines are cooled by air. In
this system the outside surfaces of the cylinder are shaped in a
series of radiating fins
with a large area of metal to radiate heat from the cylinder.
Other engines are water-cooled
and have their cylinders enclosed in an external water
In automobiles, water is
circulated through the jacket by means of a water
pump and cooled by passing through the finned
coils of a radiator.
engines and turbines,
develop no torque
when starting, and therefore provision must be made for turning the
crankshaft so that the cycle of operation can begin. Automobile
engines are normally started by means of an electric
motor or starter
that is geared to the crankshaft with a clutch that automatically
disengages the motor after the engine has started.
complete each cycle, a four-stroke reciprocating engine uses four
movements of the piston, two toward the head (closed head) of the
cylinder and two away from the head.
four strokes are:
Compression, Power and Exhaust.
piston travels down on the Intake stroke, up on the Compression stroke,
on the Power stroke and up on the Exhaust stroke.
The Piston Works
First Stroke: The
first stroke of the cycle is the intake stroke. The crankshaft,
located directly below the cylinders
on some cars and below and between the cylinders on others, turns and
begins to pull the piston
down the length of the cylinder. We'll start with the piston at its
highest point, referred to as top-dead-center. From this point the
piston begins traveling down the cylinder, it forms a vacuum. The
intake valve (see intake system)
opens when the piston begins its downward movement, and air and fuel
are drawn into the void.
engine is designed to time the intake with the downward travel of
the piston so that the whole time the piston moves downward, the
air/fuel mixture is filling the vacuum in the cylinder. The intake
valve shuts when the piston is at the bottom of the cylinder. This is
called the intake stroke.
continues to spin, forcing the piston
to rise, again through the connecting
compressing the particles of gasoline and air now in the cylinder
from the intake stroke.
This compression of the air and fuel mixture will create a more
forceful explosion. This is called the compression stroke. The
compression stroke ends when the piston has returned to its position
at the top of the cylinder.
amount that the mixture is compressed is determined by the
compression ratio of the engine. The compression ratio on the
average engine is in the range of 8:1 to 10:1.
means that when the piston reaches the top of the cylinder, the
air-fuel mixture is squeezed to about one tenth of its original volume.
Firing Stroke or The Power Stroke
the finish of the compression
stroke, a pulse of high voltage (see
ignition system) is sent to the spark
plug(located near the top of the cylinder),
causing a spark to jump across the gap between the electrodes. This
spark ignites the air-fuel mixture. The fuel explodes and the hot
gases expand, forcing the piston
down the cylinder (the path of least resistance). This turns
and gives the car the power to move forward.
timing of the combustion is such that the explosion of the air-fuel mixture
for approximately the same amount of time that it takes for the
piston to reach the bottom of its travel.
piston fires at a different time, determined by the engine firing
order. By the time the crankshaft completes two revolutions, each
cylinder in the engine will have gone through one power stroke.
the air-fuel mixture has burned, the byproducts of the combustion
must be removed from the combustion
chamber. This is handled during the exhaust stroke.
As the rotating crankshaft
again pushes the piston
upward after the power
stroke, the exhaust
valve opens to allow the burned exhaust gas to be
expelled to the exhaust system, allowing the piston to push the
exhaust gasses out of the combustion chamber so that a fresh air-fuel
mixture can be drawn in on the next intake
stroke. The exhaust valve remains open until the
top-dead-center at which point it closes. The engine is now ready
for the next intake stroke starting the four stroke process over again.
contains so much pressure, when the valve opens, the gas is expelled
with a violent force - that
is why a vehicle without a muffler sounds so loud.
This cycle is repeated over
and over again as the engine runs.
Since most cars have 4, 6,
or 8 cylinders,
each cylinder will go through these same 4 cycles.
Normally, each cylinder is
timed such that there is equal crankshaft
rotation between the power
strokes of each cylinder, allowing a smoother
the whole description in simpleterms:
lid of the can is the piston,
the container itself is the engine
block, and the hole into which the piston fits is the cylinder.
And the energy generated by the explosion must be converted over and
over from the reciprocating motion of the piston into the rotary
motion of the crankshaft.
is pretty much the same motion you use to pedal a bike:
knee goes up and down while your foot pedals 'round and 'round.
The rotating crankshaft
of the engine transfers the linear motion of all of an engine's pistons
into a circular motion,
but that motion must
be transferred from the engine to the wheels of the car.
This is dealt within the drive
The drivetrain is comprised
of the transmission, differential, and various axle and drive shafts,
each of which has its own specific purpose.
Each is a vital link
in getting rotational energy from the car's engine to its wheels.
If any of these fails
or is omitted, the car simply would not move.
engine uses that energy to
make the wheels turn.
enters the engine through the air
cleaner and proceeds to the throttle
plate. You control the amount of air that passes
through the throttle plate and into the engine with the gas
pedal. It is then distributed through a series
of passages called the intake
manifold, to each cylinder.
some point after the air cleaner, depending on the engine, fuel is
added to the air-stream by either a fuel
in older vehicles, by the carburetor.
You have just read in detail about The Internal
which is found underneath the hood of your vehicle.
spark plug supplies the spark that ignites the air/fuel mixture so
that combustion can occur. The spark must happen at just the right
moment for things to work properly.
A controlled burning takes place in the cylinder just above the piston.
The exhaust, the garbage, leaves
through the exhaust port and travels down the exhaust pipes.
from the newly created gases rapidly expanding push down on the
piston, creating downward motion. Because the pistons are each
connected to the crankshaft
at different points, these downward movements turn this crankshaft.
The pistons push the
crankshaft, and downward movement becomes circular movement.
that downward power has been changed to rotating power-a key
technological advance paralleling the invention of the light bulb!
The number of times the crankshaft revolves in a minute from this
pushing is recorded by your dashboard's tachometer in revolutions per
minute (rpm) (see
"tach" needle will hover around 800 when the engine is at
idle, 2,000 when coasting, 2,500+ for accelerating or driving uphill.
rotating crankshaft rotates the flywheel.
The now rotating flywheel has lots of surface area from which the
transmission can physically pick up and transmit this rotating power
to the wheels.
end result is that everything, including the wheels, rotates. And
wheel rotation moves the car. It is sort of like a domino reaction,
where one moving domino causes the next one to move. Here, the power
from the piston causes the crankshaft to move, which causes the
flywheel to move, then the transmission, then the drive axles, then
by attaching a belt (NOT the timing
Belt mentioned earlier)
to the end of this revolving crankshaft, this rotating movement is
utilized by other parts of the car.
example, the now rotating belt moves the water pump, whose job it is
to circulate the coolant through the engine. The belt also turns the alternator,
which generates electricity for the battery and spark
engines work in a different way.
rotary, or Wankel, engine has no piston, it uses rotors instead (usually
two). This engine is small, compact and has a curved, oblong
inner shape (known as an "epitrochoid" curve). Its
central rotor turns in one direction only, but it produces all four
strokes (intake, compression, power and exhaust) effectively.
are several piston engine types which are identified by the number
of cylinders and the way the cylinders are laid out. Motor vehicles
will have from 3 to 12 cylinders
which are arranged in the engine
block in several configurations.
core of the engine is the cylinder,
with the piston
moving up and down inside the cylinder. A car has more than one
cylinder (four, six and eight cylinders are common).
a multi-cylinder engine, the cylinders usually are arranged in one
of three ways:
or flat (also known as horizontally opposed or boxer)
most popular of them are shown on the left.
An inline 4 cylinder engine
A V-6 cylinder engine
A flat 4 cylinder engine
In-line engines have the
cylinders arranged, one after the other, in a straight line. In a
vertical position, the number of cylinders used is usually either
four or six, but three cylinder cars are becoming more common.
The V-type of engine has
two rows of cylinders at (usually) a ninety degree angle to
each other and is commonly
used in V-6, V-8, V-10 and V-12 configurations.
Its advantages are its
short length, the great rigidity of the block,
its heavy crankshaft,
and attractive low profile (for a car with a low hood). This type of
engine lends itself to very high compression ratios without block
distortion under load, resistance to tensional vibration, and a
shorter car length without losing passenger room.
In 1914, Cadillac was the first company in the
United States to use a V-8 engine in its cars.
horizontal-opposed engine is like a V-type
engine that has been flattened until both banks lie
in a horizontal plane. It is ideal for installations where vertical
space is limited, because it has a very low height.
engines are less common than the other two designs. They are
used in Subaru's and Porsches in 4 and 6 cylinder arrangements as
well as in the old VW beetles with 4 cylinders. Flat engines
are also used in some Ferrari's with 12 cylinders.
purpose of the engine block is to support the components of the
engine. Additionally, the engine block transfers heat from friction
to the atmosphere and engine coolant.
is the difference between a small block and a big block? How
about a short block and a long block?
Block: An engine WITHOUT the head(s). Usually includes the
crankshaft, camshaft, and pistons.
An engine WITH the head(s). Usually does not include the oil pan,
valve covers, and manifolds.
Block: The smaller of a manufacturers two series of engines. In
the case of Chevy, the small block includes the 262, 265, 267, 283,
302, 305, 307, 327, 350, and 400.
The larger of a manufacturers two series of engines. In the case of
Chevy, the 366, 396, 402, 427, and 454.
the overlap of small and big block displacements. Note also that a
small block can be a long block.
terms define different characteristics of the engine.
cylinder is a round hole through the engine
bored to receive a piston (See
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.
for other purposes, such as aviation, are arranged in other assorted forms.
diameter of the cylinder is called the "bore" while its
height is called its "stroke." The "displacement"
of an engine is actually a reflection of the total amount of volume
of the engine's cylinders, and nothing to do with the actual size of
the engine itself (although the two are highly correlated). The
displacement is simply the bore multiplied by the stroke of a single
cylinder, multiplied by the total number of cylinders in the engine.
Muscle car engine displacements were usually measured in cubic
inches, while modern vehicle's are expressed in terms of liters.
Roughly 61 cubic inches equals a liter of displacement. Therefore, an
engine with 350 cubic inches of displacement would be the equivalent
of 5.7 liters.
Cylinder Head is the top cap for the engine
cylinder head is the metal part of the engine that encloses and
covers the cylinders.
on to the top of the block, the cylinder head contains combustion
valves (in overhead-valve engines).
seals the passages within the head-block connection, and seals the
cylinders as well.
Ford sold his first production car, a 2-cylinder Model A, on July
cylinder head contains at least one intake
valve and one exhaust
valve for each cylinder. This allows the air-fuel
mixture to enter the cylinder and the burned exhaust gas to exit the
cylinder. Most engines have two valves per cylinder, one intake
valve and one exhaust valve.
newer engines are using multiple intake and exhaust valves per
cylinder for increased engine power and efficiency.
engines are sometimes named for the number of valves that they have
such as "24 Valve V6" which indicates a V-6 engine with
four valves per cylinder. Modern engine designs can use
anywhere from 2 to 5 valves per cylinder.
valves are opened and closed by means of a camshaft. A camshaft is a
rotating shaft that has individual lobes for each valve. The
lobe is a "bump" on one side of the shaft that pushes
against a valve lifter moving it up and down.
the lobe pushes against the lifter, the lifter in turn pushes the
valve open. When the lobe rotates away from the lifter, the
valve is closed by a spring that is attached to the valve.
A very common configuration is to have one camshaft located in the engine
block with the lifters connecting to the valves
through a series of linkages. The camshaft must be synchronized
with the crankshaft
so that it makes one revolution for every two revolutions of the crankshaft.
most engines, this is done by a "Timing Chain" (similar
to a bicycle chain) that connects the camshaft with the
crankshaft. Newer engines have the camshaft located in the cylinder
directly over the valves. This design is more efficient but it
is more costly to manufacture and requires multiple camshafts on Flat
and V-type engines. It also requires much longer timing
chains or timing
belts which are prone to wear.
engines have two camshafts on each head, one for the intake
valves and one for the exhaust
valves. These engines are called Double
Overhead Camshaft (D.O.H.C.) Engines while the other type is called
Single Overhead Camshaft (S.O.H.C.) Engines. Engines with the
camshaft in the block are called Overhead Valve (O.H.V) Engines. Gaskets
head gasket is the gasket that separates the head of your engine
from the block.
also separates the coolant channels from the oil channels.
The small holes that you see
around the piston
holes are oil and coolant channels that allow the engine coolant to
flow around the pistons for better cooling of the engine.
the factories bolt the engine's head and block together, a small
piece of rubbery material. the gasket is placed in between for a
tightly sealed fit. Gaskets insure a firm seal. Occasionally, gaskets
deteriorate to the point where they leak, particularly on very old
cars and highly stressed racing cars. Perhaps you have heard someone
say that their engine "blew a gasket" or has a "blown
and seals are needed in your engine to make the machined joints
snug, and to prevent fluids and gasses (oil, gasoline, coolant,
fuel vapor, exhaust, etc.) from leaking.
has to keep the water in the cooling system at the same time as it
contains the combustion pressure. Gaskets made of steel, copper and
asbestos are used between the cylinder head and engine block. Because
the engine expands and contracts with heating and cooling, it is easy
for joints to leak, so the gaskets have to be soft and
"springy" enough to adapt to expansion and contraction.
also have to make up for any irregularities in the connecting parts.
engines have the camshaft mounted above, or over, the cylinder
instead of inside the block (OHC "overhead camshaft" engines).
This arrangement has the advantage of eliminating the added weight
of the rocker arms and push
rods; this weight can sometimes make the valves
"float" when you are moving at high speeds. The rocker arm
setup is operated by the camshaft lobe rubbing directly on the
rocker. Stem to rocker clearance is maintained with a hydraulic valve
lash adjuster for "zero" clearance.
overhead camshaft is also something that we think of as a relatively
new development, but it's not. In 1898 the Wilkinson Motor Car
Company introduced the same feature on a car.
double overhead cam shaft (DOHC) is the same as the overhead
camshaft, except that there are two camshafts instead of one.
an overhead valve (OHV) engine, the valves are mounted in the cylinder
above the combustion
chamber. Usually this type of engine has the camshaft
mounted in the cylinder block, and the valves are opened and closed
by push rods.
engines have more than one valve; "multivalve" refers to
the fact that this type of engine has more than one exhaust or intake
valve per cylinder.
that opens to permit the fuel mixture into the cylinder.
engines have more than one intake valve to each cylinder .
valve used to open and close the valve port entrances to the engine cylinders. The
valvetrain's only job is to let air and fuel in and out of the
engine at the proper time. The timing is controlled by the
camshaft which is synchronized to the crankshaft
by a chain or belt.
cars built before the 1990s need to have their "timing"-
the rhythm of the cams and crankshafts-adjusted once in a while. On
some cars you need only a timing light (less
and a screwdriver. Newer
cars are computer-controlled and need no adjustments
valve train is a precisely-timed mechanism made up of valves, rocker
arms, pushrods, lifters, and the camshaft.
function of the valvetrain is to allow fuel and air into the engine
at the appropriate time. The camshaft controls the timing but this is
synchronized to the crankshaft by the timing
which is often referred to as the fan belt.
are constantly being redesigned so that they are lighter and have
relatively flat torque curves. Engine management systems improve
engine economy and responses. Engines have been made quieter by
introducing a torque roll axis mounting system which reduces engine vibrations.
crankshaft converts the up and down (reciprocating) motion of
into a turning (rotary) motion.
provides the turning motion for the wheels.
the pistons move up and down, they turn the crankshaft just like
your legs pump up and down to turn the crank that is connected to the
pedals of a bicycle.
crankshaft is usually either alloy steel or cast iron.
crankshaft is connected to the pistons by the connecting-rods.
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.
speed at which the crankshaft spins is measured in revolutions per
minute (RPMs). Most drivers run their engines at three to five
thousand RPMs. When the driver puts their foot on the accelerator, it
lets more gasoline and air into the engine. Since most cars have
computerized fuel delivery systems, instead of carburetors, the
amount of air let in and fuel released is carefully calculated.
flywheel is a fairly large wheel (a
that is attached
to the rear of the
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
Then it uses some of this energy to drive the crankshaft, connecting
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.
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.
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
chamber is the area where compression
and combustion take place. As the piston
moves up and down, you can see that the size of the combustion
chamber changes. It has some maximum volume as well as a minimum volume.
difference between the maximum and minimum is called the
displacement and is measured in liters or CCs (Cubic Centimeters,
where 1,000 cubic centimeters equals a liter).
are some examples:
chainsaw might have a 40 cc engine.
motorcycle might have a 500 cc or a 750 cc engine.
sports car might have a 5.0 liter (5,000 cc) engine.
normal car engines fall somewhere between
liter (1,500 cc) and 4.0 liters (4,000 cc)
you have a 4-cylinder engine and each cylinder
displaces half a liter, then the entire engine is a "2.0 liter
engine." If each cylinder displaces half a liter and there are
six cylinders arranged in a V configuration, you have a "3.0
the displacement tells you something about how much power an engine
can produce. A cylinder that displaces half a liter can hold twice as
much fuel/air mixture as a cylinder that displaces a quarter of a
liter, and therefore you would expect about twice as much power from
the larger cylinder (if everything else is equal).
a 2.0 liter engine is roughly half as powerful as a 4.0 liter engine.
can get more displacement in an engine either by increasing the
number of cylinders or by making the combustion chambers of all the
cylinders bigger (or both).
the name suggests, this is the area where the compressed air/fuel
mixture is ignited and burned.
location of the combustion chamber is the area between the top of
at what is known as TDC (top dead center) and the cylinder
TDC is the piston's position when it has reached the top of the cylinder,
and the center line of the connecting
is parallel to the cylinder walls.
two most commonly used types of combustion chamber are the
hemispherical and the wedge shape combustion chambers.
hemispherical type is so named because it resembles a hemisphere. It
is compact and allows high compression with a minimum of detonation.
The valves are placed on two planes, enabling the use of larger
valves. This improves "breathing" in the combustion
chamber. This type of chamber loses a little less heat than other
types. Because the hemispherical combustion chamber is so efficient,
it is often used, even though it costs more to produce.
wedge type combustion chamber resembles a wedge in shape. It is part
of the cylinder head. It is also very efficient, and more easily and
cheaply produced than the hemispherical type.
is a unit of power for measuring the rate at which a device can
perform mechanical work. Its abbreviation is hp or bhp (for
brake horse power).
One horsepower was defined as the amount of power needed to lift
33,000 pounds one foot in one minute.
rings provide a sliding seal between the outer edge of the piston
and the inner edge of the cylinder.
The rings serve two purposes:
keep oil in the sump from leaking into the combustion area, where it
would be burned and lost.
cars that "burn oil" and have to have a quart added every
1,000 miles are burning it because the engine is old and the rings no
longer seal things properly.
pin connects the piston
to the connecting
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
refers to the delivery of the ignition spark, or the opening and
closing of the engine valves, depending on the piston's
position, for the power
The timing chain is driven by a sprocket on the crankshaft
and also drives the camshaft sprocket.
automobile engine uses a metal timing chain, or a flexible toothed timing
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.
Rods attach the valve lifter to the rocker arm. Through their
centers, oil is pumped to lubricate the valves and rocker arms. '
recent development is the serpentine belt, so named because they wind
around all of the pulleys driven by the crankshaft pulley.
design saves space, but if it breaks, everything it drives comes to a stop.
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.
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.
keeps the crankshaft operation calm.
A 4 cylinder engine produces a power
every half crankshaft
revolution, an 8 cylinder, every quarter revolution. This means
that a V8 will be smoother running than a 4. To keep the
combustion pulses from generating a vibration, a flywheel
is attached to the back of the crankshaft. The flywheel is a
disk that is about 12 to 15 inches in diameter. On a standard
transmission car, the flywheel is a heavy iron disk that doubles as
part of the clutch system. On automatic equipped vehicles, the
flywheel is a stamped steel plate that mounts the heavy torque converter.
flywheel uses inertia to smooth out the normal engine pulses.
Shaft Some engines have an inherent rocking motion that
produces an annoying vibration while running. To combat this,
engineers employ one or more balance shafts. A balance shaft is a
heavy shaft that runs through the engine parallel to the crankshaft.
This shaft has large weights that, while spinning, offset the
rocking motion of the engine by creating an opposite rocking motion
of their own.
is the unwanted byproduct. Engineers design a car to diffuse the
heat quickly and efficiently before it damages or melts the engine.
known as antifreeze),
stored in the radiator, flows through passages in the engine around
where it absorbs heat from the combustion mixture. Coolant is part
water, and part pure coolant (ethylene
a chemical makeup allowing optimum heat absorption. The coolant
carries this heat through hoses to the radiator where flowing air
removes the heat, restoring the coolant to its original temperature,
and leaving it ready to absorb more heat. This continuous closed
cycle of heat transportation prevents the engine from melting
together or seizing up due to the extremely high temperatures
produced from combustion (1,000
The water pump, running from the belt system, helps circulate this coolant.
you need heat in the passenger area, you are asking that some of
this same heat be diverted to your space. (By
the way, coolant retains its "antifreeze" name because it
also prevents this water mixture from freezing up into an ice cube in
the winter time.)
stored in the oil pan below the engine, flows through its own
passages in the engine's
absorbing and transferring heat. More importantly, oil prevents heat
buildup by reducing friction. If you rub your hands together, note
how quickly they generate heat and become warm. Friction produces
heat. If you were to cover your hands in vegetable oil first, the
result of rubbing would be little or no heat because direct contact
between your hands is reduced. Vacuum
run on a vacuum system.
vacuum exists in an area where the pressure is lower than the
atmosphere outside of it. Reducing the pressure inside of something
causes suction. For
example, when you drink soda through a straw, the atmospheric
pressure in the air pushes down on your soda and pushes it up into
same principal applies to your engine. When the piston
travels down in the cylinder
it lowers the atmospheric pressure in the cylinder and forms a
vacuum. This vacuum is used to draw in the air and fuel mixture for
combustion. The vacuum created in your engine not only pulls the fuel
into the combustion
it also serves many other functions.
running engine causes the carburetor and the intake manifold to
produce "vacuum power," which is harnessed for the
operation of several other devices.
is used in the ignition-distributor vacuum-advance mechanism. At
part throttle, the vacuum causes the spark to give thinner mixtures
more time to burn.
positive crankcase ventilating system (PCV) uses the vacuum to
remove vapor and exhaust gases from the crankcase.
vapor recovery system uses the vacuum to trap fuel from the
carburetor float bowl and fuel tank in a canister. Starting the
engine causes the vacuum port in the canister to pull fresh air into
the canister to clean out the trapped fuel vapor.
from the intake manifold creates the heated air system that helps to
warm up your carburetor when it's cold.
EGR valve (exhaust-gas recirculation system) works, because of
vacuum, to reduce pollutants produced by the engine.
air conditioning systems use the vacuum from the intake manifold to
open and close air-conditioner doors to produce the heated air and
cooled air required inside your vehicle.
manifold vacuum also is used for the braking effort in power brakes.
When you push the brake pedal down, a valve lets the vacuum into one
section of the power-brake unit. The atmospheric pressure moves a
piston or diaphragm to provide the braking action.
produces its own combustion recipe at its own separate time dictated
by the firing order. For example, my 1984 Chevy Pick Up firing order
This firing information can be
found just inside the hood on one of those numerous stickers,
or in any manual specific to your vehicle.
firing order means that cylinder one burns or fires its mixture
first, then cylinder four, then cylinder two, then cylinder five,
etc. until it goes back to cylinder one and repeats the whole
process. Your car's computer makes sure that each cylinder has the
necessary mixture at the right time.
Control Module (PCM)
on "valve timing" to open their ports at the correct time
for the air and fuel ingredients. Valve timing at this point is
mechanically controlled by the camshaft. But the spark
needs to know when to ignite the mixture, matching the valve
openings, and so relies on the "ignition timing" set by the
may not be computer literate, but your car is. All cars nowadays
have a computer tucked away under the dash or hood. Known as the
powertrain control module (PCM), this computer insists on the most
precise combustion mixture to insure the best gas mileage and reduce
tailpipe pollutants. The computer has its eyes and ears around the
car via its sensors which are strategically placed in order to
capture certain data.
this manner, the PCM controls the amount and timing of combustion
ingredients, and therefore, the final results.
PCM also provides important data to you via your dashboard gauges,
needles, and lights.
are many variations among dashboards-some use a light
place of a gauge and vice versa,
combine the two into one general purpose dash indicator.
with your driver's manual for an accurate understanding of your
specific gauges and lights.
engine" light flags an oil, coolant, or engine problem that
needs immediate attention. Treat this light very seriously!
some older cars, this light may identify an oil, coolant, or
cars use the separate,
"service engine" light for emissions-related problems. The golden/orange-colored
"service engine" light may also illuminate if there is a
computer problem. Either is hazardous both to your engine and your
emissions system and will increase air pollution out the tailpipe.
Again, this light requires prompt attention.
oil gauge shown above
reveals oil pressure. Some gauges show oil level instead, some show
an oil can
check your driver's manual for variations.
car may not have either one, relying entirely on the red engine
light for oil problems.
battery gauge above
indicates the battery charge, which should hover between 12.6 and
14.5 volts. Anything over 14.5 volts is too much for your car's computer.
temperature gauge registers your engine's temperature.
rpm needle (tachometer) measures the revolutions of your crankshaft.
your car is equipped with an antilock brakes system (ABS),
the ABS light may come on initially as the computer checks the system.
should then go out.
same goes for the airbag light, again,
your car is equipped with one or more airbags.
form a combustion seal and transmit forces from combustion to the connecting
The piston is a partly hollow, cylindrical shaped piece of metal
that fits relatively tightly inside a cylinder.
common engines have 4, 6, or 8 pistons which move up and down in the cylinders.
the upper side of the piston is what is called the combustion
chamber where the fuel and air mix before
ignited. On the other side is the crankcase which is full of
oil. Pistons have rings which serve to keep the oil out of the
combustion chamber and the fuel and air out of the oil.
the pistons in the engine are connected through individual
connecting rods to a common crankshaft.
engine has a number of systems that help it do its job of converting
fuel into motion. Most of these subsystems can be implemented using
different technologies, and better technologies can improve the
performance of the engine. Here's a look at the different subsystems
used in modern engines:
charge first flows to a distributor, which you can easily find under
the hood of most cars. The distributor has one wire going in the
center and four, six, or eight wires (depending
on the number of cylinders)
out of it.
ignition wires send the charge to each spark plug. The engine is
timed so that only one cylinder receives a spark from the distributor
at a time. This approach provides maximum smoothness.
combustion engines must maintain a stable operating temperature, not
too hot and not too cold. With the massive amounts of heat that
is generated from the combustion process, if the engine did not have
a method for cooling itself, it would quickly self-destruct.
Major engine parts can warp causing oil and water leaks and the oil
will boil and become useless.
cooling system in most cars consists of the radiator and water pump.
Water circulates through passages around the cylinders and then
travels through the radiator to cool it off.
a few cars, as well as most bikes, the engine is air-cooled instead.
You can tell an air-cooled engine by the fins adorning the outside of
each cylinder to help dissipate the heat. Air-cooling makes the
engine lighter but hotter, generally decreasing engine life and
cars are normally aspirated, which means that air flows through an
air filter and directly into the cylinders.
engines are either turbo charged or super charged, which means that
air coming into the engine is first pressurized (so that more air /
fuel mixture can be squeezed into each cylinder) to increase
performance. The amount of pressurization is called boost.
turbo charger uses a small turbine attached to the exhaust pipe to
spin a compressing turbine in the incoming air stream. A super
charger is attached directly to the engine to spin the compressor.
starting system consists of an electric starter motor and a starter
solenoid. When you turn the ignition key, the starter motor spins the
engine a few revolutions so that the combustion process can start.
takes a powerful motor to spin a cold engine. The starter motor must overcome:
of the internal friction caused by the piston rings.
compression pressure of any cylinder(s) that happens to be in the
energy needed to open and close valves with the cam shaft.
of the "other" things directly attached to the engine,
like the water pump, oil pump, alternator, etc.
so much energy is needed and because a car uses a 12-volt electrical
system, hundreds of amps of electricity must flow into the starter
motor. The start solenoid is essentially a large electronic switch
that can handle that much current.
you turn the ignition key, it activates the solenoid to power the motor.
Engine's Lubrication System
is the life-blood of the engine.
engine running without oil will last about as long as a human
is pumped under pressure to all the moving parts of the engine by an
lubrication system makes sure that every moving part in the engine
gets oil so that it can move easily. The two main parts needing oil
are the pistons (so they can slide easily in their cylinders)
and any bearings that allow things like the crankshaft and cam shafts
to rotate freely.
most cars oil is sucked out of the oil pan by the oil pump, run
through the oil filter to remove any grit, and then squirted under
high pressure onto bearings and the cylinder walls. The oil then
trickles down into the sump, where it is collected again and the
carburetion a device called a carburetor mixes fuel into air as the
air flows into the engine.
a fuel injected engine the right amount of fuel is injected
individually into each cylinder either right above the intake valve
(port fuel injection) or directly into the cylinder (direct fuel injection).
the garbage of the whole piston process, is vented out through the
exhaust ports to the exhaust pipes, muffler, and tailpipe.
exhaust system includes the exhaust pipe and the muffler. Without a
muffler what you would hear is the sound of thousands of small
explosions coming out your tailpipe. A muffler dampens the sound. The
exhaust system also includes a catalytic converter.
on The Webpage covering exhaust
Emission Control System
emission control system in modern cars consists of a catalytic
converter, a collection of sensors and actuators, and a computer to
monitor and adjust everything.
example, the catalytic converter uses a catalyst and oxygen to burn
off any unused fuel and certain other chemicals in the exhaust. An
oxygen sensor in the exhaust stream makes sure there is enough oxygen
available for the catalyst to work and adjusts things if necessary.
electrical system consists of a battery and an alternator.
alternator is connected to the engine by a belt and generates
electricity to recharge the battery.
battery makes 12-volt power available to everything in the car
ignition system, radio, headlights, windshield wipers, power windows
and seats, computers, etc.) through the vehicle's wiring.
So you go out one morning and
your engine will turn over but it won't start . . .
What could be wrong?
Should your mechanic ever say,
"You've got a worn piston," or "Your
block is cracked,"
now you'll know what they mean.
A worn piston means the "lid" that
converts the explosion into usable energy is allowing some of the
energy to slip by.
A cracked block means the "can" is no longer
containing the energy.
Now that you know how
an engine works, you can understand the basic things that can keep an
engine from running.
Three fundamental things can
happen: a bad fuel
mix, lack of compression
or lack of spark.
Beyond that, thousands of minor things can create problems, but
these are the "big three."
Based on the simple engine we
have been discussing,
here is a quick
run-down on how these problems affect your engine:
1. Bad fuel mix - A
bad fuel mix can occur in several ways:
You are out of gas, so the
engine is getting air but no fuel.
The air intake
might be clogged, so there is fuel but not enough air.
The fuel system might be
supplying too much or too little fuel to the mix, meaning that
combustion does not occur properly.
There might be an impurity in
the fuel (like water in your gas tank) that makes the fuel not burn.
2. Lack of compression
- If the charge of air and fuel cannot be compressed properly, the
combustion process will not work like it should. Lack of compression
might occur for these reasons:
are worn (allowing air/fuel to leak past the piston
The intake or exhaust valves
are not sealing properly, again allowing a leak during compression.
The most common
"hole" in a cylinder occurs where the top of the cylinder (holding
the valves and spark plug and also known as the cylinder
attaches to the cylinder itself. Generally, the cylinder and the
cylinder head bolt together with a thin gasket
pressed between them to ensure a good seal. If the gasket breaks
down, small holes develop between the cylinder and the cylinder head,
and these holes cause leaks.
3. Lack of spark - The
spark might be nonexistent or weak for a number of reasons:
If your spark
plug or the wire
leading to it is worn out, the spark will be weak.
If the wire is cut or
missing, or if the system that sends a spark down the wire is not
working properly, there will be no spark.
If the spark occurs either
too early or too late in the cycle (i.e. if the ignition timing is
off), the fuel will not ignite at the right time, and this can cause
all sorts of problems.
Many other things can go
wrong. For example:
If the battery is dead, you
cannot turn over the engine to start it.
If the bearings that allow
to turn freely are worn out, the crankshaft cannot turn so the engine
If the valves do not open and
close at the right time or at all, air cannot get in and exhaust
cannot get out, so the engine cannot run.
If someone sticks a potato up
your tailpipe, exhaust cannot exit the cylinder so the engine will
If you run out of oil, the piston
cannot move up and down freely in the cylinder, and the engine will seize.
In a properly running engine,
all of these factors are within tolerance.
As you can see, an engine has
a number of systems that help it do its job of converting fuel into
motion. Most of these subsystems can be implemented using different
technologies, and better technologies can improve the performance of
DETECT ENGINE PROBLEM
Try and detect the problem -
is the car not starting, running roughly, conking out, or using too
After you have detected it,
isolate the system most likely to be its cause. If it is conking out,
the fuel system may be at fault. If it is not starting, the
electrical system may be worth looking at first. If the car is
overheating, check the cooling system.
After you have isolated the
most likely system, locate the weakest link in that system. The fuel
pump, for example, is often the most vulnerable part of the fuel system.
Check each successive part in
the system until the problem is solved.
Get the broken part replaced
or repaired. Consult your car's manual for other specific problems
you might be facing.
This will help to speed
Problems you might encounter with the mentioned parts
The rings over time tend to wear out. When they wear they allow
the fuel and air to enter into the oil and dilute it. This
dilution reduces the oils ability to lubricate your engine and can
cause premature wear. Also if the rings wear down they can
allow oil from the crankcase to enter the combustion chambers.
This will result in oil being burned and exiting your tailpipe as
grayish/white smoke. If your car spews grayish white smoke and
it does not go stop in the first few minutes after start-up you might
have worn rings. If the smoke goes away after start-up look to
the valvetrain section.
The crankshaft rides on bearings which can wear down over time.
The bearings support the crankshaft and also the rods which connect
the pistons to the crankshaft. A loud medium pitched knocking
noise in the engine points to warn bearings most of the time.
This is usually a costly repair and involves removing the crankshaft
and either machining the surface where the bearings ride, or
replacing the entire crankshaft. To prevent this type of
problem, use a high quality oil, change your oil at suggested
intervals (3 months or 3000 miles is a safe number) and always
maintain your oil level between oil changes.
Remember the oil smoke problem mentioned above in the piston
sections. If your car only smokes grayish/white smoke at
start-up you may have leaking valve seals. Valve seals keep oil
from above the valve from leaking into the combustion
When they wear, they can allow oil to seep into the combustion
chamber and collect there until your start the engine again.
You generally do not get oil leaking past the valve seals while the
engine is running since the seals expand with the heat of the engine
and plug the leak.
Another common problem is the timing chain or belt will slip or even
break causing the cam shaft to stop rotating. Remember the
camshaft tells the valves when to open and if it stops spinning then
the valves stop opening and closing. No valve moving, no engine
A term you will here when talking about timing chains and belts is
"interference engine". When an engine is an
"interference engine" the pistons and valves are so close
together that if the valves were to stop moving (broken belt or chain) and
kept spinning they would crash into the piston. (that's the interference)
This crash tends to do bad things to an engine, breaking valve,
bending pushrods, and even cracking pistons. This is why most
manufacturers recommend changing the timing chain or belt every
60,000 miles. timing
dry out, stretch and deteriorate over time so even if you do not have
60,000 miles on the car think about changing the belt after it's 6
your Engine Condition on a Regular Basis
most of engine breakages happen as the result of the owner's
mistakes. If your car has run well for many years, you might find
yourself skipping a fluid check or putting longer periods of time
between the engine servicing's. Today, with self-service gas stations
everywhere, often the only way you will insure your car's fluids are
at proper levels is to do it yourself. If you don't, you may miss a
minor defect, for example, a coolant leakage. A few weeks later, lack
of the coolant causes your engine to overheat and eventually you are
faced with engine damage. And then even after that repair, other
small problems surface and you find that your car breaks down more often.
important for you to safeguard your vehicle investment by checking
your engine condition on a regular basis.
Needed to Keep the Engine in Good Condition?
only few basic conditions are needed for long engine life:
listen for noises when your engine is running. The engine should run
evenly and you should not hear any strong noises, knocking, pinging,
or whistling while the engine is idling or during
acceleration. After it's warmed up, try to press
accelerator harshly for a second. The engine should accelerate
quickly, without delays or hesitation. There should be no loud noises
while accelerating. The idle should be stable during a stop. There
should be no smoke coming out from the tail pipe (only steam
during warming up or in cold weather is permissible).
the instrument panel. All the warning lights on the instrument panel
for low oil pressure, check engine, overheating, etc should go off
after the engine is started and should not come on while the engine
the hood and look at the engine. A good engine should be dry. It may
be dusty, but it should not be oily, and it should not have any
leaks. Check the engine thoroughly for oil leaks. The more leaks, the
more damage your engine may have.
performing routine engine maintenance and tune ups, cleanings,
adjustments, and necessary replacements, check for the following:
Filter: A dirty fuel filter may cause unexpected engine stalling
and loss of engine power.
Filter: A dirty air filter dirty air filter causes loss of
engine power, increased fuel consumption, etc
can give significant enhancement of engine performance.
Belt damage can cause serious engine damage, especially if it's a
Coolant: Old coolant loses its anticorrosive and other characteristics.
The objective of this Web Page is to familiarize you with basic auto maintenance
- in some common emergencies - not to make you an expert in auto mechanics
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I am in no way, shape, or
form telling you to do this yourself. Your results may vary. If
something goes wrong, it is not my fault! These are just guidelines.