Modern fuel injection is a beautiful thing. Electronic impulses tell your injectors exactly when to open, how long to stay open, and when they need to close, and best of all – each of these events can be completely controlled by you through your laptop. It’s a great thing, as long as every part of the system is doing its job in exactly the way it needs to, and it’s easy to forget that just because EFI systems are so technologically advanced doesn’t mean that they don’t still need occasional maintenance.
Probably the most common parts of an EFI system to need serviced are the fuel injectors. They can get clogged, stick open or closed, and over time the spray pattern and flow rate will just naturally degrade and greatly reduce fuel injectors’ consistency. Thankfully, under most circumstances fuel injectors can easily regain their original functionality with a simple cleaning and flow test to ensure proper function.
During a recent dyno tuning session with our Project BlownZ 4th Gen drag car, Horsepower Connection‘s Brian Macy was explaining the benefits of injector flowing and cleaning. BlownZ has a 1,300 horsepower 388ci ProCharged LSX, and every component of our fuel system needs to be functioning at full capacity. So, just to make sure we had all of our bases covered, we took BlownZ’s fuel injectors to RC Engineering, in Torrance, California for a good cleaning and flow test.
The injector test stand allows both a precise measurement of the volume of fuel delivered as well as a direct view of the injector's spray pattern.
We talked with John Park at RC Engineering, who gave us the low down on the how and why of fuel injector flow testing. “The first thing we do is a baseline flow test of the injectors.” Park says. “Flow testing of the injector takes place on our custom made flow bench using using an EFI Technology ECU.” This step is simply to get a look at how the injectors are performing in their current state.
In the ultrasonic bath the injectors are cycled on and off, allowing the cleaning solution to get into every crevice and break loose every minute piece of gunk.
After they have their baseline from the initial flow test, the next process involves cleaning all the injectors in an ultrasonic-bath. So what exactly is an “ultrasonic bath”? Basically, an ultrasonic machine cycles sound waves through the injector cleaning solution at frequencies above the range of human hearing. This vibrates the bath and creates an immense amount of energy that can clean inside the smallest crevices. Park tells us, “The injectors are pulsed on and off during the process in the ultrasonic machine to make sure all the moving parts get thoroughly cleaned.”
The next process is one of the most important. The guys from RC take every injector and record the spray pattern and check for any leaks after the cleaning. “The next process takes place on the single pattern tester with the injector filter removed and back flushed.” Park tells us. “After cleaning you’ll see what the injectors should have been functioning like in the first place, and they will be restored back to spec.”
This is one of RC's stands for testing the flow and spray pattern of multiple injectors at once.
One of the big things you should be looking for from your injectors is flow consistency across the board. You want the system to be balanced with as little spread in the difference of flow rates as possible. Park says, “In a street car, the spread might go as high as four or five percent but, a race application like BlownZ, you want it under a two percent spread.” As you can tell from our before and after flow charts, BlownZ’s injectors did pick up some measurable amount of flow from RC’s cleaning and testing. Our overall system balance improved from 1.6 % to an absolutely stellar 0.3%. Additionally, the BlownZ’s injectors had their spray pattern upgraded from “Good” to “Excellent.”
Here you can see just how many CC/Min. each one of BlownZ's injectors gained from cleaning and testing at RC Engineering. John Park also let us in on an easy way to convert CC/Min to Lbs/Hr. - simply divide by 10.5. That means that BlownZ's injectors are flowing around 160 Lbs./Hr!
You’ll also notice that the amount of horsepower the injectors can support at a given Brake Specific Fuel Consumption number also went up a good bit thanks to the added flow. Since BlownZ’s engine is supercharged, it’s BSFC is a bit higher, likely around the 0.65 mark. According to RC’s flow charts, that means that our injector set flows enough fuel to handle about 1,576 horsepower – right in the ball park for what we are aiming to make at the crank.
These BSFC horsepower ratings are based on how much power the injectors could support at 80% duty cycle to give a nice safety cushion.
If you’ve got a high horsepower late model that relies on fuel injectors to keep it well fed with the good stuff, you might want to consider having them professionally cleaned and flow tested. As you can see from our results, you might gain a bit more flow, and if nothing else you can have peace of mind that your entire fuel system is up to snuff. For more info on cleaning and flow testing fuel injectors, check out RC Engineering’s website.