SYSTEM / ECM System Fuel Injection Timing Control Purpose: Calculates the best fuel injection timing. Operation: 1. ECM calculates the fuel injection timing according to engine speed and fuel injection amount. 2. ECM controls the two-way valve in injector by turning ON/OFF according to fuel injection timing. Fuel Injection Rate Control Purpose: Improves combustion in the engine cylinder. Operation: 1. The injector injects small amount of fuel (pilot in- jection) first and ignites. 2. After igniting, the injector injects fuel (main injec- tion). 3. ECM controls fuel injection timing and fuel injec- tion amount by turning the two-way valve in in- jector ON/OFF. Fuel Injection Operation 1.
The nozzle in injector is always pressured. 2. When turning the two-way valve ON, high-pressure fuel in the control chamber flows through orifice 1. 3. Therefore, the hydraulic pressure piston is raised and the nozzle opens so that the injection starts. 4. When turning the two-way valve OFF, high-pressure fuel from the common rail flows to the control chamber through orifice 2. 5. Therefore, high-pressure flows to the control chamber and the hydraulic pressure piston is lowered. 6. Consequently, the nozzle is closed and injection stops. T2-3-8