The quantity control in overrun mode function is described by way of example on engine 926.9 (6 cylinder).
G07.15-A029-79
A3 | Drive control (CPC) control unit | Y602 | Cylinder 3 single injection pump | |
A6 | Engine management (MR) control unit | Y603 | Cylinder 4 single injection pump | |
CAN 4 | Drive train CAN | Y604 | Cylinder 5 single injection pump | |
Y600 | Cylinder 1 single injection pump | Y605 | Cylinder 6 single injection pump | |
Y601 | Cylinder 2 single injection pump | B | Output signals |
Overrun mode, shown on single injection pump for cylinder 1 |
2 | High pressure pipe |
3 | Connection fitting |
4 | Fuel injector with nozzle holder assembly |
5 | Pump element |
6 | Supply passage |
7 | Solenoid valve |
8 | High pressure chamber |
9 | Diversion chamber |
10 | Return flow passage |
Y600 | Cylinder 1 single injection pump |
B | Fuel feed |
D | Fuel return |
G07.15-A022-82
If the vehicle is in overrun mode, i.e. the target engine torque requested by the drive control (CPC) control unit is smaller than the current actual engine torque, solenoid valves (7) are not actuated in the single injection pumps for cylinders 1 to 6.
The single injection pumps for cylinders 1 to 6 cannot build up the fuel pressure required to achieve injection since the fuel from high pressure chamber (8) is first pushed by the upwards movement of pump element (5) through opened (deenergized) solenoid valve (7) into diversion chamber (9) and then into return flow channel (10).
In this way, the fuel pressure which is applied over high-pressure lines (2) and connection fitting (3) to the injection nozzles in the fuel injectors with nozzle holder combinations (4) is not sufficient to lift the nozzle needle against the spring force of the compression spring from its seat. This means that the opening pressure of the injection nozzles is not reached and no injection occurs.
This improves the exhaust characteristics of the engine, increases the braking effect of the engine and significantly reduces fuel consumption.