Here are two stock Acura Integra fuel injectors. They may look the same, however testing them proved one is clearly outperforming the other. The trick to “parts-bin tuning” is to find more injectors, test them, and get a matching set.

Some NASA racing classes mandate you use certain stock OEM parts on your racecar. Any solid racing mechanic can tell you not all stock parts are created equal. The trick is to use the best stock parts to make your racecar legal and as fast and efficient as possible. To do this, you want to do something called “parts-bin tuning.”

AJ Gracy’s fuel injector cleaner and tester at his shop, Performance In-Frame Tuning, is the key to parts-bin tuning because we can measure the output of each injector compared with others at the same time. The machine allows you to make a multitude of adjustments for testing and takes the guesswork out of how your injectors are performing.

I learned the fine art of parts-bin tuning back in the old Cub Scout days racing in the prestigious Pinewood Derby. If you wanted to legally win the Pinewood Derby, you needed to purchase about 10 Pinewood kits. Sifting through all of the different wheels, you would find some wheels were junk. Some wheels were perfectly round while others had impurities from the molding process, making them not as round and thus not as fast. Putting together the best four wheels out of 10 kits could ensure a victory in the gravity-powered downhill race. How much difference does this process make? Well, the proof is in our trophy case: This method earned my son a district championship.

We decided to use this same method for finding the best stock fuel injectors. In NASA’s Honda Challenge 4 class, rules specifically prohibit the upgrading of fuel injectors from non-OEM parts. Instead of just resting on our laurels and driving a car with four stock fuel injectors of unknown performance, we decided to inspect our injectors, flow test them, and then use the parts-bin tuning method to install four high-performing matching injectors.

You can clearly see the number three injector is not flowing as much fuel as its counterparts. This means this cylinder will run lean. This injector’s next stop: the trash can.

Our first step was to go to NASA racer AJ Gracy’s shop, Performance In-Frame Tuning, in Napa, Calif. AJ owns a cool device that lets you test injectors, see their spray pattern, and verify their output. He also can clean injectors to improve their performance. We ripped the injectors out of our Acura Integra and put them on his machine to see where our baseline was.

We saw some concerning data. The spray pattern on one injector didn’t look healthy while another injector wasn’t pushing as much fuel as the rest of its teammates. This creates a bad situation where one cylinder could be running lean, causing less performance, over-heating issues, and possible damage to the engine block.

If you look carefully at the spray pattern of the far-right injector, it looks a bit splotchy. We want to ensure the spray pattern in the intake manifold is nice and ionized so it mixes well with the air as it enters the combustion chamber. We decided to toss this injector in the trash, too, and try to find a better replacement.

This sent us to our local Pick-Your-Part to grab as many stock OEM fuel injectors out of Acura Integras as we could find and then start the process of parts-bin tuning to get the best-matched four injectors possible. If you are a dedicated wrecking yard nerd, like myself, a nice inexpensive toolkit with a carrying case is a must have. Never head to the wrecking yard with only the two wrenches you “think” are all you need to remove a fuel rail. Inevitably, you will need another tool. Bringing a small basic tool kit is a life saver. I never leave home without it.

Before heading to the wrecking yard to search for some much-needed fuel injectors, I ensured that I had the tools I needed to disassemble a car in the middle of a dirt lot. There is nothing worse than needing a tool you don’t have. Inexpensive and easy to carry, tool kits like this one are a must-have at the wrecking yard.
After wandering around the wrecking yard for a bit, I found just what I wanted, a DA Integra with four fuel injectors still mounted in the intake manifold. A few turns of the wrench and “Come to papa,” I had four injectors to take back to the shop to clean and test.

After our little scavenger hunt, we checked each injector with a volt meter to ensure it was the correct one for an Acura Integra. You never really know what you will get at a wrecking yard. After determining the injectors we mined were correct, we were back to the flow test to match four good injectors. AJ cleaned the injectors, put them on his machine, and after a few different tests, and some swapping around, we found four matching injectors.

Once we were back from the wrecking yard with our new (old) injectors, it was time to use AJ’s machine and clean up the injectors before testing them. This process only takes around five to 10 minutes.
To ensure the injectors we found in the wrecking yard were correct, we checked the resistance with a multimeter to ensure they were consistent with the year of manufacture of the car. The resistance should have been between 10-13 ohms. These were testing right at 11.8, which was perfect.

We replaced all of the seals with brand new rubber and slapped our matched set of injectors into our Honda B18A1 engine. We put the Integra on AJ’s chassis dyno to measure our improvements. The good news is we made more power and we were able to do it legally and inexpensively, a win-win in our book. More power from a few parts from a wrecking yard? How can you beat that?

After reassembling the Integra with our new, cleaned, blueprinted, and matched stock injectors, we put the car on the chassis dyno at Performance In-Frame Tuning to measure any performance gains. The good news is we found horsepower using inexpensive parts from a wrecking yard.
After cleaning, swapping and testing, we finally found four stock fuel injectors that had good spray patterns and flowed an equal amount of fuel. As you can see in this photo, all four injectors produced the same level of fuel flow. Awesome.


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Image courtesy of Rob Krider