Electronic Fuel Injection - Injector Sequencing

Electronic Fuel Injection is the obvious solution to modern engine fueling and ignition delivery.

There are dozens of areas within subject of electronic fuel injection where a little more insight will give you big advantages in terms of power, idle quality and fuel consumption, when you configure and tune electronic fuel injection systems.

This post is a brief introduction to the area of Injector Sequencing for your Aftermarket Electronic Fuel Injection System. This is a very advanced part of electronic fuel injection installation and configuration. It will run though the reasons why you would want to sequence your injectors, and a couple of the specific ways you can sequence them, depending on your application. If we don't go through your specific setup, don't worry, just drop by www.wolfems.com and let us know about your application. We will be able to work with you to determine the injector sequencing to best suit your engine.

First of all, lets talk about sequential vs banked or grouped injection.

Banked injection - is where more than 1 injector is pulsed at the same time. On some early fuel injected cars, the injectors on all 4 or 6 or 8 cylinders, were pulsed together. This can lead to fuel mixtures varying from cylinder to cylinder, as there is no control over when in the engine cycle, the injection pulse occurs for each cylinder.

Sequential injection - Every cylinder has its own injector, and that injector is opened at the same point in the engine cycle as the engine rotates. It is pulsed once for every two engine revolutions.

Let's look at an example of sequential injection on a 4 cylinder engine with the firing order of 1-3-4-2.

You will want to ensure that your injectors are pulsed in that same order.

That sounds simple. And it is. But how do you work out where to pulse each injector in the engine cycle? Do you pulse an injector when the intake valve is open or closed?

Lets take a quick look at what happens when the engine is starting, as that is the most critical situation for injector sequencing. That is because the injector pulse takes up a very small amount of engine rotation at that engine speed.

This is more critical in some engines than others, depending on the physical placement of the injectors, and the shape of the intake system.

Imagine the intake valve is closed. There is no airflow. The injector is pulsed. The fuel sprays out of the injector, and some of it hits the other side of the intake runner, and pools there. Some of the fuel that you thought you were injecting is now sitting on the bottom of the intake runner.

This may happen a few times while you crank the engine, until it starts, at which time there may be enough airflow to suck the pooled fuel into the cylinder, making it stumble (since this pooled fuel is not atomized, but rather, it is huge drops).



One the other hand. Picture that the intake valve is open, and that the air is rushing past the tip of the injector, and into the cylinder as the piston moves down the bore.

The injector pulses, and as it does so, the atomized fuel is sucked straight into the cylinder by the inrush of air.

All of the fuel that the injector delivered is now in the cylinder, and ready to be ignited by the ignition system.



Obviously, the best solution is to have the injector pulse when the valve is open and the air rushing past the tip of the injector can transport the fuel into the combustion chamber.

And this basic theory applies to engines with any number of cylinders. So long as you have a camshaft pulse that you can synchronize off, you can setup your injectors to pulse sequentially, giving you the most control over the fuel delivery to your engine.

Sequential injection is the ultimate electronic fuel injection system.