Denso 4D56 - Fuel Injection Rate Control; Outline

Operation Section
1
–
35
12. FUEL INJECTION RATE CONTROL
12.1 Outline
z While the injection rate increases with the adoption of high-pressure fuel injection, the ignition lag, which is the delay from the time
fuel is injected to the beginning of combustion, cannot be shortened to less than a certain value. As a result, the quantity of fuel that
is injected until main ignition occurs increases, resulting in an explosive combustion at the time of main ignition. This increases both
NOx and noise. For this reason, pilot injection is provided to minimize the initial ignition rate, prevent the explosive first-stage com-
bustion, and reduce noise and NOx.
Normal Injection
Pilot Injection
Large First-stage
Combustion
(NOx and Noise)
Small First-stage
Combustion
Injection Rate
Heat Release
Rate
-20 TDC 20 40
Crankshaft Angle (deg)
-20
TDC 20 40
Crankshaft Angle (deg)
QD2362E