4-Stroke Diesel Engine Principles - Yanmar 1GM10 Shop Manual

SINGLE-CYLINDER ENGINES
As the piston travels downward, the exhaust
valve closes and the intake valve opens,
allowing air to be drawn into the cylinder. When
the piston reaches the bottom of its travel
(BDC), the intake valve closes and remains
closed for the next 1 112 revolutions of the
crankshaft.
As the piston almost reaches the top of its
travel, the injector sprays fuel into the
combustion chamber. The fuel is ignited by the
heat of compression. The piston continues to
top dead center (TDC) and is pushed downward
by the expanding gases.

4-STROKE DIESEL ENGINE PRINCIPLES

When the crankshaft continues to rotate, the
piston moves upward, compressing the air.
Exhaust valve
When the piston almost reaches BDC, the
exhaust valve opens and remains open until the
piston is near TDC. The upward travel of the
piston forces the exhaust gases out of the
cylinder. After the piston has reached TDC, the
exhaust valve closes and the cycle repeats.
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