Intake Manifold.

Custom Search

Back
Figure 4-12. Bellows-Type Electric Fuel Pump.

Up
TM-9-8000 Principles of Automotive Vehicles Manual

Next
Figure 4-15. Ram Induction Manifold

TM 9-8000

atmospheric pressure. This is important for the following

(1) Deliver the mixture to the cylinders in equal

reasons:

quantities and proportions. This is important for smooth

engine performance. The lengths of the passages

(1) Air must be allowed to enter the tank as the

should be as near to equal as possible to distribute the

fuel is pumped out. Without ventilation of the tank, the

mixture equally.

pressure in the tank would drop to the point where the

fuel pump would not be able to draw any more fuel from

(2) Help to keep the vaporized mixture from

it. In some cases, the higher pressure around the

condensing before it reaches the combustion chamber.

outside of the tank could cause it to collapse.

Because the ideal mixture should be vaporized

completely as it enters the combustion chamber, this is

(2) Temperature changes cause the fuel in the

very important. To reduce the condensing of the mixture,

tank to expand and contract. Absence of a ventilation

the manifold passages should be designed with smooth

system could cause excessive or insufficient fuel line

walls and a minimum of bends that collect fuel. Smooth

pressure.

flowing intake manifold passages also increase

volumetric efficiency (para 2-23).

b. Configurations. The most common methods of

(3) Aid in the vaporization of the mixture. To do

venting a fuel tank are:

this, the intake manifold should provide a controlled

system of heating (para 7-3). This system of heating

(1)

By venting the fuel

tank cap to the

must heat the mixture enough to aid in vaporization

atmosphere. This method was the

most common on

without heating to the point of significantly reducing

earlier passenger cars and trucks.

It still is used on

volumetric efficiency (para

vehicles that are not subject to

emission control

2-23).

regulations or used for fording.

b. Ram Induction (Fig. 4-15). Intake manifolds can

(2) By providing a line to the fuel tank that vents

be designed to provide optimum performance for a given

the fuel tank at a point that is high enough to prevent

engine speed range by varying the length of the

water from entering during fording operations.

passages. The inertia of the moving intake mixture will

cause it to bounce back and forth in the manifold

(3) Vehicles that are subject to emission control

passage from the end of one intake stroke to the

regulations have fuel tank ventilation systems that work

beginning of the next intake stroke. If the passage is the

in conjunction with the evaporation control system. This

proper length so that the next intake stroke is just

system is discussed in paragraph 7-5.

beginning as the mixture is rebounding, the inertia of the

rnixture will cause it to ram itself into the cylinder. This

45. Intake Manifold.

will increase the volumetric efficiency of the engine In the

designated speed range. It should be noted that the ram

a. Description (Fig. 4-14). The intake mani-

manifold

fold should:

Figure 4-14. Typical Intake Manifold.

4-9