Fuel Injector: Description and Operation

Fuel Injector:

The injection valve consists of a valve body and needle valve with fitted solenoid armature. The valve body contains the solenoid winding and the guide for the needle valve. When there is no current in the solenoid winding the needle valve is pressed against its seat on the valve outlet by a helical spring. When a magnetic field is generated in the solenoid winding the needle valve is lifted by approx. 0.1 mm and the fuel can flow out through a calibrated annular orifice. The front end of the needle valve is provided with a specially ground pintle for atomizing the fuel. The open time of the valve lies in the range of 1 to 1.5 ms. To achieve good fuel distribution with low condensation loss, wetting of the intake manifold walls must be avoided.

Injection View:

A particular spray angle in connection with a particular distance of the injection valve from the intake valve must be maintained. The fuel injection valves are a push fit into the intake manifold and are held in place by the injection rail. Large rubber O-rings at the inlet and outlet of the fuel injector provides insulation against heat which prevents the formation of fuel-vapor bubbles and guarantees good hot-starting characteristics. The rubber O-rings also ensure that the injection valves are not subjected to excessive vibration.
The injection valves receive power from the DME main relay and are operated by ground pulses from the DME control unit. The duration of injection is determined from various inputs to the DME control unit.