Lesson 2/Learning Event 1
The multifuel engine is presently used in 2 1/2-ton and some 5-ton wheeled vehicles. These wheeled vehicles
use a turbocharged (forced air intake) engine. Both engines are the same size, but the turbocharged engine
produces more power. With the exception of the air intake systems, both engines operate on the same
principles.
Basically, the multifuel engine is made the same as most four-stroke-cycle diesel engines. The major difference
is the design of the air intake and combustion chamber. A ball-shaped combustion chamber pocket is located
in the top of the piston to permit burning of various fuels.
Let's take a closer look at a typical multifuel engine. Each letter and number contained in the identification
number of the engine has a specific meaning. For example, for the LDS 465-1A engine used in the 5-ton
truck, "L" means liquid-cooled, "D" means diesel, and "S" means supercharged. The 465 is the model number
of the engine, and the 1A means a change has been made in the basic engine model.
Now let's take a look at the-operating principles. First, on the intake stroke, air is drawn through the open
intake valve. The intake passages in the intake manifold and valve port openings are made so they cause the air
to swirl or spin around in the cylinder as it enters. The air swirls with such force that it will continue to do so
for sometime.
On the compression stroke the piston moves up, and both valves are closed, as in other engines. The air swirl
continues throughout this stroke and also throughout the next.
As the piston nears the top of the intake stroke, fuel is injected by the fuel injector nozzle. It is injected onto
the walls of the combustion chamber pocket in the piston head. A small amount of this injected fuel turns to
vapor and starts to burn due to the extreme heat of compressed air. About 95 percent of the fuel settles in the
lower part of the combustion chamber pocket. Oil spraying on the bottom of the piston head cools the
combustion chamber pocket walls so all the fuel will not burn immediately
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