Operation Section
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(4) Fuel Injection Rate Control
• Although the injection rate increases with the adoption of high-pressure fuel injection, the ignition lag, which is the
delay from the start of injection to the beginning of combustion, cannot be shortened to less than a certain period of
time. Therefore, the quantity of fuel injected until ignition takes place increases (the initial injection rate is too high),
resulting in explosive combustion simultaneous with ignition, and an increase in NOx and sound. To counteract this
situation, pilot injection is provided to keep the initial injection at the minimum requirement rate, to dampen the primary
explosive combustion, and to reduce NOx and noise.
Q000895E
Injection Rate
Heat Release Rate
Large First-Stage
Combustion
Small First-Stage
Combustion
Crankshaft Angle (deg) Crankshaft Angle (deg)
-20 TDC 20 40 -20 TDC 20 40
[Ordinary Injection]
[Pilot Injection]
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