Chapter 3 Engine Classifi cation, Parts Identifi cation 57
The combustion chamber wedge is formed by the
angled cylinder and a piston with an inverted V
top. This setup will also produce a squish effect.
The spark plug is generally located at one
corner of the wedge, Figure 3-20. This pro-
vides a smooth fl ame travel and loads (presses
down) the piston gradually. When the charge is
fi rst ignited, it loads only a portion of the pis-
ton. This partial pressure starts the piston down
smoothly. As the piston begins to travel down,
the fl ame front spreads across the entire piston
dome, providing smooth loading.
Cylinder Classifi cation
Cylinder placement gives rise to one of the
most common methods of engine classification.
Many arrangements have been used, but only
those in popular use today will be covered in
this text.
Inline Engine
The inline engine has its cylinders arranged
one after the other in a straight line. They are in
a vertical, or near vertical position, Figure 3-21.
Most modern inline engines are four cylinders.
Inline six-cylinder engines were used in older
vehicles and can still be found in a few modern
light trucks. Until the adoption of the V-8, eight
cylinder inline engines were common. A few
three- and fi ve-cylinder inline engines are now
produced. A variation of the inline engine is the
slant or inclined, engine. An inclined engine is
an inline engine with the cylinder block slanted
to one side. This is done to fi t the engine into
a smaller engine compartment, allowing for a
lower hood line.
V-Type Engine
A V-type engine places two banks or rows
of cylinders at an angle to each other—gener-
ally at 60° or 90°. The V-type engine has several
advantages: short length, extra block rigidity,
a short, heavy crankshaft, and low profi le that
allows low hood lines. The shorter block permits
a reduction in vehicle length with no sacrifice in
passenger room.
Valves
Hemispherical
combustion
chamber
Figure 3-19.
A cutaway view of a hemispherical combustion chamber.
The valves are set in two planes.
TRW, Inc.
Wedge
combustion
chamber
Figure 3-20.
Notice that the head in this wedge combustion chamber
is fl at and cylinder block is machined at an angle—
approximately 10°. The valves are set in a plane.
Goodheart-Willcox Publisher
Figure 3-21.
Crankshaft, connecting rods, and pistons of an inline,
four-cylinder engine.
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