a. Design Features of the 6V53T Engine (model #5393). Examining
the design features of the 6V53T diesel engine will help you to grasp
its operational characteristics.
b. The Two Stroke Cycle.
In a two-cycle engine, intake and
exhaust take place during part of the compression and power strokes
respectively (Fig. 2).
The following paragraphs explain the
principle this engine uses for operation.
o Scavenging. The blower forces fresh air into the cylinders
to expel exhaust gases and to supply the cylinders with
fresh air for combustion. The cylinder wall contains a row
of ports that are above the piston when the piston is at
the bottom of its stroke.
These ports admit air from the
blower into the cylinder when the piston uncovers the
ports. The flow of air to the open exhaust valves, at the
top of cylinder, produces a scavenging effect (pushing the
exhaust gases out of the cylinder through the open exhaust
valves). The exhaust valves close and the blower continues
to force fresh air into the cylinder.
The piston begins
its upward stroke and covers the inlet ports leaving the
cylinder full of fresh air.
o Compression. As the piston continues its upward stroke, it
compresses the charge of fresh air. Just before the piston
reaches its highest point, top dead center (TDC), the fuel
injectors inject the required amount of fuel into the
cylinder.
The heat created during compression of the air
ignites
the
fine
spray
immediately,
and
continues until the fuel-air mixture burns completely.
o Power.
The resulting pressure forces the piston downward
on its power stroke. The exhaust valves open approximately
half-way down allowing the burned gasses to escape into the
exhaust manifold.
Shortly thereafter, the downward moving
piston uncovers the inlet ports sweeping the cylinder with
fresh scavenging air.
This entire cycle takes one
revolution of the crankshaft or two strokes.
Hence the
name "two-stroke cycle."
c. The Fuel System.
This system consists of a fuel pump,
strainer, filter, injectors, and related fuel lines.
A restricted
fitting in the fuel junction box, mounted on the oil cooler housing
assembly, maintains pressure within the fuel system.
The fuel pump
takes fuel from the vehicle's fuel tank through the strainer and
circulates it through the filter.
From the filter, the fuel goes
through the fuel lines and fuel inlet
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OD1713
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