Operation Section
1
–
4
1.4 Common Rail System Characteristics
z The common rail system uses a type of accumulation chamber called a rail to store pressurized fuel, and injectors that
contain electronically controlled solenoid valves to inject the pressurized fuel into the cylinders.
z Because the engine ECU controls the injection system (including the injection pressure, injection rate, and injection tim-
ing), the injection system is independent and thus unaffected by the engine speed or load.
z Because the engine ECU can control injection quantity and timing to a high level of precision, even multi-injection (mul-
tiple fuel injections in one injection stroke) is possible.
z This ensures a stable injection pressure at all times, even in the low engine speed range, and dramatically decreases
the amount of black smoke ordinarily emitted by a diesel engine during start-up and acceleration. As a result, exhaust
gas emissions are cleaner and reduced, and higher power output is achieved.
(1) Features of Injection Control
Injection Pressure Control
• Enables high-pressure injection even at low engine speeds.
• Optimizes control to minimize particulate matter and NOx emissions.
Injection Timing Control
• Enables finely tuned optimized control in accordance with driving conditions.
Injection Rate Control
• Pilot injection control injects a small amount of fuel before the main injection.
· Injection pressure is more than double the current
pressure, which makes it possible to greatly reduce
particulate matter.
Common Rail System
Injection Pressure Control Injection Timing Control Injection Rate Control
Injection Quantity Control
Electronic Control Type
Common Rail System
Conventional
Pump
Optimized and Higher Pressure
Speed
Speed
Injection Quantity
Injection Pressure
Pre-Injection
Pilot injection
After-Injection
Post-Injection
Main Injection
1324
Injection Pressure
Particulate
Injection Rate
Crankshaft Angle
Cylinder Injection Quantity Correction
Injection Quantity
Advance Angle
Q000751E
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