ENGINE MEASUREMENTS AND
ARRANGEMENT OF CYLINDERS
PERFORMANCE
Engines are also classified according to the
LEARNING OBJECTIVE: Identify various
arrangement of the cylinders. One classification is the
engine measurements.
"in-line," which has all cylinders cast in a straight line
above the crankshaft. Another classification is the
As an AS, you will have to know the various ways
V-type, which has two banks of cylinders mounted in a
in which engines and engine performance are
V-shape above the crankshaft. While these are the two
measured. An engine may be measured in terms of
most common or typical arrangements (fig. 3-9), you
cylinder diameter, piston stroke, and number of
might work occasionally with a horizontally opposed
cylinders. It may be measured, performance wise, in
engine, whose cylinders are mounted in two side rows,
terms of the torque and horsepower it develops and in
each opposite a central crankshaft.
efficiency. These various terms, their meanings, and
their application are discussed here. Also, there are a
The cylinders are numbered. The cylinder nearest
few engineering terms you will need to know.
the front of an inline engine is number 1. The others are
numbered 2, 3, 4 etc., from front to rear. In V-type
DEFINITIONS
engines, the numbering sequence varies with the
manufacturer. You can find the correct order in the
You should be familiar with the following
technical manual for the engine.
definitions:
The firing order (which is different from the
WORK. Work, in the mechanical sense of the
numbering order) of the cylinders of most of the
term, is done when a resistance is overcome by a force
engines with which you will be working is stamped on
acting through a measured distance. When a weight is
the cylinder block or on the manufacturer's nameplate.
lifted from the ground, work is done on the weight. It is
If you are unable to find the firing order, and no
moved upward against the force of gravity. When a tow
operation or instruction manual is at hand to guide you,
tractor pulls an aircraft, work is done. If a 1-pound
turn the engine over by the crankshaft and watch the
weight is lifted 1 foot, 1 foot-pound of work is done.
order in which the intake valves open.
ENERGY. Energy is the ability to do work. When
VALVE ARRANGEMENT
work is done on a body, energy is stored in that body.
The higher a weight is lifted from the ground, the more
The majority of internal combustion engines are
energy is stored in the weight. Then, when it falls, it will
classified according to the position and arrangement of
strike the ground hard; that is, it will do more work on
the intake and exhaust valves; that is, whether the
the ground.
valves are in the cylinder block or in the cylinder head.
POWER. Power is the rate at which work is done.
Various arrangements are used in classifying the
It takes more power to work rapidly than to work
engines.
slowly. Engines are rated in terms of the amount of
Q3-6. Which of the following methods is the most
work they can do per minute. An engine that can do
common method of classification of an
more work per minute than another is said to be more
engine?
powerful.
1.
The type of cooling
HORSEPOWER. The work capacity of an engine
2.
The valve arrangement
is measured in horsepower. Horsepower (hp) is the
3.
The type of fuel used
power of a horse, or a measure of the rate at which a
4.
The cylinder arrangement
horse can do work. An average horse can lift a weight of
(B) V-TYPE
(A) IN-LINE
ASf03009
Figure 3-9.--Typical cylinder arrangements.
3-9
