As the air passes over the oil reservoir, most of
the particles will not be able to make the turn, and they
will hit the oil and be trapped.
As the air continues upward and passes through
the filter element, the smaller particles that bypassed the
oil will be trapped.
The air keeps the element soaked with oil by
creating a fine spray, as it passes the reservoir.
The air then makes another 180-degree turn and
enters the carburetor.
The dry-type air cleaner passes the incoming air
through a filtering medium before it enters the engine.
The air filter contains a ring of filter material (fine-mesh
metal threads or ribbons, pleated paper, cellulose fiber,
or polyurethane), as shown in figure 4-16. These types
of filter materials provide a fine maze that traps most of
the airborne particles.
The air cleaner also muffles the noise of the intake
air through the carburetor or fuel injection system,
manifold, and valve ports. This noise would be very
noticeable if it were not for the air cleaner. In addition
the air cleaner acts as a flame arrester in case the engine
backfires through the intake manifold. The air cleaner
prevents the flame from escaping and igniting gasoline
fumes outside the engine.
What fuel additive is used to prevent engine ping
Q2. What is the measurement of the ability of
gasoline to resist knock or ping?
What device is used to prevent the accidental use
of leaded fuel in a vehicle designedfor unleaded
What are the two types of air cleaners currently
PRINCIPLES OF CARBURETION
LEARNING OBJECTIVE: Describe the
operating systems and principles of a simple
carburetor and a computerized controlled
carburetor. Identify the different carburetor
accessories and their functions. Identify and
describe possible carburetor troubles and
quick system checks.
The principles of carburetion are presented so you
may better understand the inner workings of a
carburetor and how the other components of the fuel
system function to provide a combustible mixture or air
and fuel to the engine cylinders.
Air is composed of various gases, mostly nitrogen
and oxygen (78 percent nitrogen and 21 percent oxygen
by volume). These gases are, in turn, made up of tiny
particles called molecules. All substances, whether
solid, liquid, or gas, are made up of molecules. In solids,
such as ice or iron, the particles are held closely together
so that they seem to have no motion. In liquids, the
molecules are not held together tightly, so they can
move freely with respect to each other. In gases, there is
still less tendency for the molecules to bond; therefore,
the molecules can move quite freely. The molecules of
gas are attracted to the earth by gravity or by their
weight. It is the combined weight of the countless
molecules in the air that make up atmospheric pressure.
Evaporation is the changing of a liquid to a vapor.
The molecules of the liquid not being closely tied
together are constantly moving among themselves.
Any molecule that moves upward with sufficient speed
will jump out of the liquid and into the air. This process
will cause the liquid to evaporate over a period of time.
The rate of evaporation is dependent on the following:
TEMPERATURE. The rate of movement of the
molecules increase with temperature. Because of this,
Figure 4-16.Dry-type air filter.