TM 5-3895-346-14
ENGINE OVERHAUL
PRINCIPLES OF OPERATION
PRINCIPLES OF OPERATION
Shortly before the piston reaches its highest position, the required amount of fuel is sprayed into the
combustion chamber by the unit fuel injector as shown in Fig. 1 (power). The intense heat generated during
the high compression of the air ignites the fine fuel spray immediately. The combustion continues until the
injected fuel has been burned.
The resulting pressure forces the piston downward on its power stroke. The exhaust valves are again opened
when the piston is about half way down, allowing the burned gases to escape into the exhaust manifold as
shown in Fig. 1 (exhaust). Shortly thereafter, the downward moving piston uncovers the inlet ports and the
cylinder is again swept with clean scavening air. This entire combustion cycle is completed in each cylinder for
each revolution of the crankshaft, or, in other words, in two strokes; hence, it is a two-stroke cycle.
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