Air Filters - OD16200026

Principles of Gasoline And Disesel Fuel Systems
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through the intake manifold on its way to the radiator.

a. Purpose. The air filter fits over the engine air intake to filter

out particles of foreign matter. Any foreign matter that enters the intake

will act as an abrasive between the cylinder walls and the pistons, greatly

shortening engine life. Two types of filters in use are the wet the and dry

types.

b. WetType. The wettype, or oil bath air filter, consists of the

main body, the filter element that is made of woven copper gauze, and the

cover. Operation is as follows: The incoming air enters between the cover

and the main body. It is pulled down to the bottom of the main body, where

it must make a 180 turn as it passes over the oil reservoir. As the air

passes over the oil reservoir, most of the particles will not make the turn;

they will hit the oil and be trapped. As the air continues upward and

passes through the filter element, smaller particles that bypassed the oil

will be trapped. The air keeps the filter element soaked with oil by

creating a fine spray as it passes the reservoir. The air finally makes

another 180 turn and enters the carburetor.

c. DryType (figure 9 on the following page). The drytype air filter

passes the incoming air through a filtering medium before it enters the

engine. The filtering medium consists of oilsoaked copper mesh or

replaceable pleated paper, the latter being the most common.

Principles of Carburetion

a. Composition of Air. Air is composed of various gases, mostly

nitrogen and oxygen (78 percent nitrogen and 21 percent oxygen by volume).

These gases are composed of tiny particles called molecules as are all

substances. In the air surrounding the earth, the molecules are able to

move quite freely in relation to each other as in all gases. The molecules

of air are attracted to the earth by gravity, creating the atmosphere. The

weight of the air molecules creates atmospheric pressure.