QUOTE(Jeff Bowlsby @ Jan 17 2015, 08:42 AM)
... the same injector can be used on a 1.6L or a 2.0L engine all else being equal, because the pulse width is determined by the ECU.
Yes, but.
A given size injector can only flow a maximum of so much fuel for a given fuel pressure. (And there are limits to the pressure; if it gets too low the fuel will dribble instead of spraying, and if it gets too high the pattern also suffers and the seals can leak.) So you can't have the injectors be too small.
You can't have them be too large, either. Metering of small amounts of fuel is difficult for large injectors, because the amount of time the injector would be open is too small. The ECU will only have a limited amount of resolution at those very short durations, and it will take a noticeable amount of time for the injector itself to open and close, and the variations in that will start to become noticeably large relative to the desired opening time.
That said, a given injector can support a variety of power levels or engine sizes.
Your point is valid in this context, but it is not a universal truth.
--DD