DELPHI IMV Inlet Metering Valve 9109-903
The Inlet Metering Valve controls rail pressure by regulating
the amount of fuel sent to the pumping components
of the HP pump. This actuator has a double role as
First it improves injection system output since the HP pump only compresses the amount of fuel needed to maintain the rail pressure required by the system.
Secondly it reduces the temperature in the fuel tank. In fact when excess fuel is sent to the return circuit, the expansion of the fluid
(from rail pressure to atmospheric pressure) involves a large amount of heat. This generates an increase in temperature of the
fuel sent back to the tank. To avoid generating too high a temperature, it is necessary to do the following:
- Cool the diesel in the exchanger (a costly, cumbersome and not very efficient solution).
- Limit the amount of heat generated by fuel expansion by reducing the rate of discharge. To reduce the rate of discharge, it is enough to adapt the HP pump output to engine needs within the whole operating range. This is what the IMV does.
The IMV is fitted to the pump hydraulic head. The transfer pump feeds fuel to it via two radial drill holes. A cylindrical filter is fitted to the IMV feed orifices. This not only protects the low pressure actuator but also protects all the injection system components downstream of the IMV.