Another question we get frequently here at Holders Diesel is, “What size injector do I go with, and more importantly what size nozzle?” We are going to cover fuel injector nozzles in this article.
Let’s start with the function of the nozzle. What does it do anyway? The nozzle is the last part of the injector before fuel enters into the cylinder to be combusted. The nozzle’s main function is to spray the fuel in the cylinder in an atomized state (a mist) so it can be easily ignited to burn and therefore run the engine to the best of its potential. So obviously, the smaller nozzle will have smaller spray orifices and the larger size nozzle will have larger spray orifices. With the same amount of injection pressure applied, the smaller nozzle will atomize the fuel better due to the smaller spray holes while the larger nozzle will not atomize as well, but it will flow more fuel in the same amount of allotted time.
What do the nozzle sizes mean? Well the % of nozzle size is just the amount of fuel that nozzle is designed to flow over stock size. For reference:
Stock - stock flow
30% - Flows 30% more than stock
75% - Flows 75% more than stock
100% - Flows 100% more than stock
And this goes on through every nozzle size.
Why is atomization of the fuel so important? When your fuel is atomized well, it burns better, cleaner, and makes good, clean power. With good atomization you will get better fuel mileage, less smoke, and lower exhaust gas temperatures. For this reason, someone using their truck mainly for towing or daily driving, without a lot of modifications, are generally happier and better off with a smaller nozzle such as a stock-30% size.
The nozzle only dictates how fast you can deliver X amount of fuel. It does not make a “stock” fuel injector flow any more fuel than it already does. It just changes the ability to empty that injector in a different amount of time. No matter who is tuning the vehicle, you cannot change the mechanical size of the injector through tuning, it is what it is. You can pull pulse width back in the tuning but the nozzles are not variable size so the fuel is just going to atomize or spray different.
So what nozzle is right for you? Well that greatly depends on what you use your truck for and what size injector you are interested in. For instance, most of our 6.0 Power Stroke injector 155cc-190cc customers run 30% nozzles and that is our most popular size nozzle. This nozzle is small enough that it still atomizes fuel well, but increases size enough to make a very noticeable difference in power. For example, a 30% nozzle has no problem flowing enough fuel to make 600 horsepower at the rear wheels. But, the real benefit to this nozzle is that it is small enough to atomize the fuel well and work well with towing and daily driving while still running clean and cool. The 30% injector nozzle is very versatile, and that is why it is our most popular.
What if you want more power than the 30% nozzle can provide you? That is where larger injector nozzles come in and shine. Maybe it’s time to go up a nozzle size, let’s talk about a 75% injector nozzle. We typically do this on our 205cc+ fuel injectors but we can accommodate any size you have in mind. The 75% fuel injector nozzle will empty the fuel quicker, so you can spray fuel into the cylinder in a shorter time. This helps significantly with making more power at higher RPM’s. This would be best suited for a competition or “hot street” diesel truck. However, the sacrifice is that although you are making more power, the truck will naturally run hotter and smokier, so it will not be as tow friendly or as ideal for daily driving. As you can see, there is some give and take with any nozzle size you choose and there is no “one size fits all”.
In short, just remember that the smaller the nozzle, the better the atomization is and the better the ability to tow and keep your exhaust gas temperatures down, while the larger nozzle will make more power when paired with the right size injector. The size nozzle you choose should reflect the modifications to your truck and what you use your truck for. You are always welcome to call us at the shop or email us if you have questions about your particular setup and uses for your truck. Just do your research and make an educated decision on injector sizing.