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Injector scaling troubles

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I've been following the courses and felt confident in my understanding of injector scaling. I watched the section in practical reflash tuning which was a worked example of fitting 1k cc injectors to a subaru (which happens to be what I'm working on at the moment as well)

The car currently has a professional tune with these injectors that I had done a while ago and it runs and logs excellent. The car's stock ROM with stock injectors also logs well and shows no problems.

In an attempt to learn and follow along, I followed the steps in the worked example - modifying my stock maps and starting with the injector flow scaling (my injector data sheet shows test results at 954cc @ 43.5psi) then decreasing the other tables referencing injector pulse width by 30%

The car will start, but will idle lean (16.5 AFR) at 25% correction. I can get the car to idle with minimum correction by setting the flow scaling to about 700cc with cruise showing about a 7-9% correction (lean) but it will then oscillate between rich and lean under any heavier load.

Is there anything I may be overlooking here? Are some vehicles more problematic than others? Any help here would be greatly appreciated!

I've never been a fan of injector scaling. I've never been happy with the results. I always seem to end up redoing the VE/Inj Time table

Lost work? Well the injectors all behave a bit differently I've found


Especially at low injector pulsewidths found at idle, recalibrating the injector dead time/latency values is really critical to informing the ECU of the characteristics of the new injectors, beyond their max flow potential.

Low injector pulse non linearity is another potential contributor to what your experiencing, but I'd start with the injector dead time/latency data and go from there.

Please keep in mind some injectors come with very accurate data that well represents them, and some do not. If yours are the latter, the behavior of the engine will not mirror the behavior shown in the course, because while rescaling the max flow potential is a key component of injector characterization, it's not the whole story.

When tuning a Subaru with ID1050xds injectors for example, following the procedures taught in the course does lead to the car starting right up with minimal fuel trims.

Just in case there's something else at play, you could double check that a mechanical issue such as an air leak wasn't perhaps accidentally induced during the injector install, perhaps at the lower injector seals where an air leak is possible without fuel leaking.

What specific injectors did you get?

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