Definition and Function of Injector Pulse Width

Because almost all gasoline-powered automobile engines currently use fuel injectors to deliver fuel to the combustion chamber. Changing load, speed, and temperature conditions require fuel delivery to be adjustable. This can be achieved by changing the pulse width of the injector. This article will show you what is the pulse width of the injector, how to determine the width, and what are Possible malfunction.

Posted on Jan 18,2021 by Sharon Wen

Injector pulse width definition

The fuel injection pulse width refers to the length of time for each fuel injection controlled by the engine on-board computer and is the most important indicator of whether the engine fuel injector is working normally.

The oil pressure in the engine oil circuit is constant, so the flow rate during fuel injection is also constant. The amount of fuel injection can only be controlled by the duration of the fuel injection. Because the electronic fuel injection nozzle of an EFI engine is opened and closed through a solenoid valve, The engine speed is high and the fuel injection time is very short. Therefore, the fuel injection signal given by the ECU is a very short pulse signal. The time width of this signal is the fuel injection pulse width.

The numerical unit of the fuel injection pulse width is milliseconds (ms). The larger the value displayed by the parameter, the longer it takes for the injector to open the fuel injection each time, and the engine will obtain a richer mixture; the smaller the parameter display value, It means that the shorter the time the injector is opened to inject fuel each time, the engine will get a leaner mixture. There is no fixed standard for the fuel injection pulse width. It will vary with the engine speed, load, and intake air volume. The ECU calculates or queries the database based on these indicators to obtain specific fuel injection pulse width values, generally the pulse width range Between 1.5ms and 2.9ms.

How to determine the pulse width of the injector

In terms of engine mechanics, determining the injector pulse width is very simple. First, determine the basic pulse width by looking at the reference table, in which the relationship between engine speed and load is explained. After determining the reference width, you can determine which factors affect engine performance, such as oxygen level and coolant temperature, and insert them into the equation “pulse width = (reference pulse) (factor A) (factor B)”.

However, in reality, the pulse width of your engine is determined by 100 or more such factors, and a reference table can be used to determine the corresponding metric for this equation. For example, in the above formula, through its reference table, the coolant temperature “coefficient A” is 75 and the value is 0.9.

Fortunately for us, the manufacturer has used this formula for many years and has continuously improved the process. Now, most cars are equipped with electronic monitors that can read out the precise measurements of all the factors that determine the pulse width. Hackers can program them by adjusting equations to improve engine performance. It is not recommended for novice mechanics or mechanics with little engine control module (ECM) experience.

Possible causes of injector pulse width

Even the smallest change in fuel injection rate will affect the performance of the engine, mainly because it is designed to operate at a certain ratio based on a variety of factors. You can observe injector problems in many ways.

For example, the smell of fuel from the engine compartment may mean that the pulse width generated by the fuel injector is too long. Engine misfire or power, acceleration, or speed reduction may be symptoms of injector failure. In any case, your vehicle has built-in safety information to prevent related spontaneous failures: the “check engine” indicator light.

If the check engine light is on, you should see a mechanic or check the engine yourself by querying the OBD-II code output by the vehicle’s ECM. If you see a code that references an injector failure, the only solution may be to replace the injector. In any case, it is best to find a mechanic for a comprehensive diagnosis and provide the most professional solution for your engine failure.

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