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Injector Operations

EFI Tuning Fundamentals

Discussion and questions related to the course EFI Tuning Fundamentals


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So of the two High and Low impedance injectors which one provides better performance? Please forgive me I am just really getting started trying to understand more of the tuning aspects of my project. In the past I have paid others to handle this aspect of my project. But after coming across HPA, I am convinced that tuning is not "Magic it's a Science" and have become more determined to learn all I can. I am currently working with a 1990 Honda CRX with a B18c swap. I was also considering removing the resistor box located to the right of the injectors. What are the possible effects or draw backs with removing the resistor box? How would it affect the operation of the injectors? Would I then by pass the resistor box and go right to the injectors? Would I need to verify the type of injector drives the ECU is using? I would like to replace the factory injectors and go with the Low Impedance. Any advice would be greatly appreciated, thank you.

Today, you can get high-flowing injectors with high impedance, and that is compatible with more ECUs. If your injectors are low-impedance, then you need to make sure your ECU can drive them (often listed as "supports peak & hold injectors"), or augment your ECU with something like this external injector driver from Acceleronics: http://www.acceleronics.com/versafueler.htm.

Adding resistors to low-impedance injectors does allow them to function, but they don't have the same capability (ie. the turn-on time may be slower, so the published battery compensation won't be correct). Yes, you can tune around this -- but why not do it right? If your setup has an external resistor box, check that you don't already have low-impedance injectors (just measure the resistance of across the two pins on the injector -- 2-4 ohms, or 12-16?).

So for your Honda, if you remove the resistor box (or perhaps leave it in place depending on the resistance) and use good high impedance injectors (like Injector Dynamics ID1050x), you will have plenty of flow capability. Is there a reason you want to use low-impedance injectors?

Back in the 80s through early 90s port fuel injectors had very large valves inside them with poor spray patterns, when you compare them to modern designs . you had 3 system designs from the factory in cars of that era:

1) high impedence injectors

2) low impedence injectors with a resistor in the harness

3) low impedence injectors with a special driver that doesn't need a resistor, called a "peak and hold" driver. This was the best design for its day, but it was more complicated and cost more money, so not many cars had them. There was a brief time in the aftermarket when special peak and hold drivers were popular, but that's not the case anymore.

in the modern era designs #2 and #3 went away at the OEM level, and then the aftermarket followed. The modern port injectors you can get are high impedence but respond better than the old low impedence + peak and hold driver.

What you want to do is get a modern injector, which are all high impedence, and bypass the resistor pack.