What is a fuel injector? The fuel injector is the last stop for fuel in your engine before it goes boom inside the combustion chamber. It is basically an electrically operated gate that opens just long enough to meter the perfect amount of fuel to run the engine. On one end of the gate is the cylinder where the gas is ignited, and on the other end is a whole bunch of gas under high pressure. When your car's brain (connected to a Mass Airflow Meter or MAF to take measurements) sends an electrical impulse to the injector, it opens the gate for an short burst of fuel.
Fuel Injectors Modification
There are a few important factors that you must take into account when modifying an electronic fuel injection engine. These automotive accessories factors are: the pulse duration of the injectors and the duty cycle. The injector pulse duration is the amount of time that the fuel injector is held open so that it can inject fuel into the combustion chamber. The pulse duration is controlled by the engine control unit (ECU) and is dependent on various sensors in the electronic fuel injection (EFI) system. The longer the pulse duration, the more fuel is added to the air/fuel mixture. The amount of fuel required at any one time varies by the amount of air flow, the air density, the engine load, and the engine temperature. Therefore the pulse duration will vary. However, there is only a limited amount of time that the fuel injector can be held open at each revolution of the engine. This amount of time is reduced as engine speed increases. For example, at 600 RPM the available time is 0.1 seconds (60 seconds in a minute divided by 600 revolutions) but at 6,000 RPM it is only 0.01 seconds.
The pulse duration relative to the available time at the engine red line is called the duty cycle and is expressed as a percentage. Thus a duty cycle of 80% means that at the engine red line the pulse duration (the amount of time the fuel injector is help open) is 80% of the available time.
Fuel Injector Duty Cycle
Some engine tuners will tell you that if your car has a duty cycle of 80%, you have a possible gain of 20%. However, performance fuel injectos are electronic solenoids and cannot be held open for too long or it will overheat and fail.