Any fool can go in and set the flow rate and the motor will run fine above 20% throttle. But if you want idle and part-throttle drivability, and especially if you want it to start quickly and smoothly, you have to have the short pulse adders and voltage offsets correct, respectively.
The way Ford labels and characterizes their injectors is really helpful - they actually have a number called MINPW which is the minimum pulsewidth the injectors will reliably fire. The last time I sized injectors for a friend's build, we were looking hard at injectors that had this data available. For this particular situation we actually discovered that a set of 80lb injectors had a lower MINPW than the 60lb injectors he was considering, even though the 60s would have met the fuel needs of the motor. Given that this was a heavy manual transmission car, I insisted that the injectors be able to reliably fuel down to 400rpm during clutch engagement, and so the 80s would have been the better choice despite their higher peak flow.
Ford also includes two slope values (a high slope and a low slope) and a transition point. This transition point is where the pulsewidth gets so short that the magnetic field delays and the pintle rise/fall times become significant relative to the requested pulsewidth. Here's an example. https://performanceparts.ford.com/pa...-9593-lu34.pdf It's at this transition point where the GM short pulse adders start to grow. There are some posts out there how to convert the elegant Ford values to the verbose GM values, but the result is perfectly characterized injectors from the first crank.
Personally I'm running 2011-2017 Ford Mustang GT injectors in my LT1 with fabulous drivability.
It continues to blow my mind how places like Racetronix advertise GM injectors with NONE of these critical parameters available. Maybe they have it on their forums, but their rules state you have to buy something before they'll give you forum access. Huh?
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