Injectors Essay

INJECTORS FUNCTIONING. MEASUREMENT OF PARAMETERS

Summary
Injectors are one of the most important components of internal combustion engines. Their task is to pump the right volume of fuel into the combustion chamber to secure an optimum combustion.
Nowadays most of the injectors are electronically actuated which has allowed a better control over them. Types of injectors
We can distinguish some types of injectors depending on these things:
• Depending of the type of injection (direct or indirect).
• Depending of the number of nozzles (single point or multipoint).
• Depending of the type of control on the fuel quantity (controlling by flow or by time).
• Depending of the variables used to calculate the mass air flow (pressure or air flow). How do they work?
An

Structure of an injector.
Page 1 of 2 Miguel Moreno Armenta
FSUPV admission task, Universitat Politècnica de València
It usually has two pins. One of them is connected to the car’s battery and the second one is connected to the ECU.
When the ECU sends a pulse to the injector, which closes the electrical circuit, the injector’s solenoid creates a magnetic field. This magnetic field attracts the needle’s magnet opening the exit orifice and letting flow the fuel.
The duration of the injection is controlled by the pulse width. How does the ECU control the injection?
The ECU enters in an internal 3D table (that engineers have previously filled in with calculated values) with three variable values: spinning regime, percentage of actuated throttle pedal and engine temperature. With these parameters the ECU looks for a value in the table and extracts an estimation of the torque.
Once the ECU has the torque value, the mass air flow control acts on the butterfly valve to reach the torque value (the open percentage of the butterfly valve and mass air flow value come from a table which is used as in the case of torque estimation). Figure 2. Control structure of