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Fuel Injector

1. What is Fuel Injector ?

A fuel injector is an electronically controlled mechanical device which is used to inject/spray (just like a syringe) the fuel into the engine for the preparation of correct air-fuel mixture which in turn provides efficient combustion to the engine.

Fuel Injector

The position of the fuel injectors differs for different engine designs but usually they are mounted on the engine head with a tip inside the combustion chamber of the engine.

Fuel Injector Location

2. Why do we need Fuel Injector ?

Fuel injectors are the necessity of all the automobile vehicles these days because:

– The working principle of internal combustion engines directly indicates that better the quality of fuel-air mixture better will be the combustion which in turn provides higher engine efficiency, so we need fuel injectors which provides far better air-fuel mixture quality than carburetors.

Brand of Fuel Injector

– The improper air-fuel mixing provided by carburetors leaves various un-burned particles inside the combustion chamber of an internal combustion engine which leads to improper propagation of combustion flame due to which  engine malfunctioning known as knocking or detonation takes place, so to avoid this almost all the vehicles on road today adopted fuel injection technology.

– The wastage of fuel in the form of carbon or un-burned particles inside the combustion chamber directly reflects the mileage of the vehicle, which is not desirable, so to avoid this, adopting fuel injection technology becomes essential.

– In case of carburetors, controlling the air-fuel mixture quality and timing(fuel metering) is not precised, the adjustments can be done mechanically, but when it comes to fuel injectors due to its smart electronically controlled unit or ECU high precision of fuel metering can be achieved

– It has been seen that not only the mileage but also the performance of the fuel injected vehicles is better than that of carbureted vehicles.

3. Types of Fuel Injectors

The advancement in fuel injection technologies gave rise to various fuel injection arrangements like throttle body fuel injection, multi-point fuel injection, sequential fuel injection and direct injection that can be used according to the application but when it comes to types of fuel injectors then it is really a tough call to categories them. On the basic of fuel injected Fuel injectors can be categorised as:

Fuel Injector

* Diesel Fuel Injector

These fuel injectors are used to inject or spray the diesel (which is heavier fuel than gasoline) directly into the combustion chamber of the diesel engine for further combustion by compression.

The capillary and nozzle of diesel fuel injectors are made in such a fashion that they can form the diesel packets while spraying the fuel inside the combustion chamber.

Diesel fuel injectors required higher injection pumping than gasoline injectors as diesel is heavier than gasoline.

Fuel Injector

* Gaosoline Fuel Injector

They are the fuel injectors used to inject or spray gasoline directly or through intake manifold into the combustion chamber for further combustion by spark.

The capillary and nozzle of gasoline fuel injectors is made smaller or same as the diesel fuel injectors depending upon the requirement.

As the gasoline is lighter than diesel, gasoline injectors required less injection pumping than diesel injectors.

Fuel Injector

4. Operating Principals Simplified

* Fuel Injector Duty Cycle          

An injector on a running engine is continually switched “ON” and switched “OFF” by the PCM. The period that the injector is switched ON during that cycle (and allowing fuel to be Injected) is classified as Duty Cycle and is calculated as a percentage.

That is: a 50% duty cycle indicates that the injector is being switched ON and OFF for the equal amount of time. A greater duty cycle increases the injector ON time.

* Injector Pulse Width

This simply refers to the amount of time measured in milliseconds (ms) that an injector stays open generally during the intake cycle. (delivers fuel) Injector pulse width for an idle condition at normal operating temp may be typically: 2.5-3.5ms. This will increase as engine load increases.

* Typical “Injector Spray Pattern Varieties”

Not all injector spray patterns are alike. Injectors are designed to supply the correct amount of fuel directed to an area as required by the manufacturer. Altering the spray pattern may affect the performance dramatically

Typical Bosch spray pattern variations


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