Basic Engine Operation Section 1:

starts with the piston at TDC.

intake stroke

is the main moving part in an engine

piston

The air-fuel mixture is uniformly mixed together to be present in the combustion chamber at a chemically exact ratio of

14.7, which is known as stoichiometric air-fuel ratio

One horsepower is equivalent to

33,000 ft

A typical automobile crankshaft will complete anywhere from _____ revolutions or more every minute

500 to 6,000

means higher thermal efficiency or that portion of the heat supplied to the engine that is turned into work.

A higher compression

is the diameter of the cylinder

Bore

shows that the pressure of a gas is inversely proportional to the volume of its containe

Boyle's law

An engine is normally described in one of two ways:

By the amount of power it produces By the size of the engine

s the ratio of the volume at BDC to the volume at TDC (clearance volume)

Compression ratio

s defined as work per unit of time. It's the rate of doing work or torque and is the unit of measurement that expresses the power output of an internal combustion engine.

Horsepower

Four Stages (Strokes) of Engine Operation

Intake, Compression, Power, Exhaust

is a complete run through all four stages of operation—intake, compression, power, and exhaust

One engine cycle

This term is used to describe an engine in which the cylinder bore diameter is exactly equal to the piston stroke dimension. When bore and stroke values are expressed, bore always appears before stroke

Square Engine

is the movement of the piston from the top to the bottom of the cylinder

Stroke

What opens to allow the exhaust gases produced by the burning mixture to exit the cylinder

The exhaust valve

What opens to allow the air-and-fuel mixture to enter the cylinder.

The intake valve

begins shortly after the spark plug arc ignites the air-fuel mixture in the combustion chamber and gasoline (reactant) burns, supported by oxygen

The power stroke

When the piston is at its highest position in the cylinder, it's said to be at

Top dead center (TDC).

is a force that tries to turn or twist something around and is defined as the product of a force and the perpendicular distance between the line of action of the force and the axis of rotation.

Torque

What is done during the intake stroke?

air that has been mixed with fuel is drawn into the cylinder.

four-stroke engine will contain at least two mechanical valves:

an intake valve and an exhaust valve

When a piston is at its lowest position in the cylinder, it's said to be at

bottom dead center (BDC)

Piston rings are designed to be springy so that

can stretch to fit over the outside of the piston and then snap back into their grooves

The space between the piston and the cylinder head when the piston is at TDC is the

clearance space or is sometimes called the compression or combustion space

The volume of this clearance space is known as the

clearance volume

The process of burning the air-and-fuel mixture in the cylinder is called

combustion

small, open space above the piston is called the

combustion chamber

The ratio of the largest cylinder volume to the smallest cylinder volume is called the

compression ratio

When the piston reaches BDC, the intake valve closes, sealing the cylinder, and the

compression stroke begins.

The connecting rods are attached to the rod journals. The main journals are used to mount the

crankshaft to the engine blockcrankshaft to the engine block

is a hollow metal tube that's drilled into the metal engine block

cylinder

In an actual engine, the top of the cylinder is sealed by a metal cover called the

cylinder head

In an automotive engine, fuel is sent directly to the _______, where it's burned inside to produce the power that's used to run a vehicle.

engine

is the volume of space that the piston must travel from the very bottom of its path to the very top of its path and is measured in units of volume

engine displacement

the size of the space inside the engine where the air-and-fuel mixture is burned. The size of this space is called the

engine displacement

In an internal combustion engine, fuel is burned inside the

engine to produce power.

The piston then begins to rise in the cylinder, beginning the

exhaust stroke

is a stroke that produces no work but expends a quantity of energy to push exhaust gases from the cylinder.

exhaust stroke

is allowed to close, by spring pressure, shortly after the piston begins its downward movement.

exhaust stroke

fuel is burned outside the engine.

external combustion engine

When the piston is at the bottom of its stroke, or BDC, the crank is at a point

farthest from the cylinder

Torque is generally expressed in

foot-pounds or Newton-meters

When a piston is in place inside a cylinder, the piston rings will press outward against the walls of the cylinder. This action helps

form a tight seal between the piston and the cylinder

the piston requires _________ to complete one full engine cycle.

four strokes

the fuel is injected directly into the combustion chamber where the air and fuel are mixed together, similar to a diesel engine.

gasoline direct injection (GDI)

There are two types of journals on a crankshaft—

he rod journals and the main journals

The sparking action of the spark plug is controlled by the engine's

ignition system

The engines that are used in automobiles

internal combustion engines.

The internal combustion engine produces

mechanical energy directly by burning fuel

When the piston is at the top of its stroke or TDC, the crank is at a point

nearest the cylinder

n a two-stroke engine, the intake and compression stages are combined and completed by

one piston stroke

When the bore is larger than the stroke, the engine is ________, and most of its power is dependent upon revolutions per minute (rpm) and generated at higher rpm values

oversquared

is a can-shaped metal component that can move up and down inside the cylinder.

piston

Note that the outside surface of a piston has several horizontal grooves cut into it. Each of these grooves holds a metal ring called

piston ring

is a circular piece of metal that's split at one point

piston ring

In the combustion chamber, a mixture of air and gasoline is burned to produce

power

the standard unit of horsepower is used to describe the

power output of a gasoline engine.

When the air-and-fuel mixture burns in the combustion chamber, it produces a small, contained explosion. The air expansion produced by this explosion is strong enough to force the piston downward in the cylinder and uses the reciprocating motion of the piston to turn the crankshaft in rotary motion, hence the term

reciprocating engine

When the piston is forced downward in the cylinder, the piston's downward motion is transferred to the

rod and crankshaft

The bottom end of the piston is connected to a

rod and crankshaft assembly

The rod and crankshaft then convert the up-and-down motion of the piston into

rotary motion

he power and exhaust stages are combined and completed by a

second piston stroke

is an example of an external combustion engine.

steam engine/ boiler

What is done during the power stage?

the air-and-fuel mixture is ignited by a spark, and the contained explosion of the fuel presses the piston back down in the cylinder.

burns fuel to produce steam, and then steam is sent to the engine to produce power.

the boiler

What is done During the exhaust stage?

the burned exhaust gases are released from the cylinder. The four stages then begin all over again

The length of the rod journal determines the

the distance the piston travels, or stroke, and is the lever

What is done during the compression stage?

the piston rises and compresses the air-and-fuel mixture that's trapped in the combustion chamber

is force (f) multiplied by length.

torque

the piston takes only _______ to complete one full engine cycle of intake

two strokes

What is the reason thatTwo-stroke engines aren't used in any current automobiles, but seen in motorcycles and small motors?

two-stroke engines aren't very fuel efficient and tend to produce more pollution than four-stroke engines

When the stroke is larger than the bore, the engine is _________, with most of its power dependent on torque.

undersquared

as defined as the product of a force and the distance through which the force acts.

work

is defined as the product of a force and the distance through which the force acts.

work