PRIN. OF INTERNAL COMBUSTION ENGINES - OD1619 LESSON 2/TASK 1
c. Ram Induction (figure 39). Intake manifolds can be designed to provide optimum
performance for a given engine speed range by varying the length of the passages.
The inertia of the moving intake mixture will cause it to bounce back and forth in
the manifold passage from the end of one intake stroke to the beginning of the next
intake stroke. If the passage is the proper length so that the next intake stroke
is just beginning as the mixture is rebounding, the inertia of the mixture will
cause it to ram itself into the cylinder.
This will increase the volumetric
efficiency of the engine in the designated speed range.
It should be noted that
the ram manifold will serve no useful purpose outside of its designated speed
As stated in paragraph 2b(3) on page 48, providing
controlled heat for the incoming mixture is very important for good performance.
The heating of the mixture may be accomplished by one or both of the following
(1) Directing a portion of the exhaust through a passage in the intake manifold
(figure 40 on the following page).
The heat from the exhaust will transfer and
heat the mixture. The amount of exhaust that is diverted into the intake manifold
heat passage is controlled by the manifold heat control valve.