Bernoulli understood all this fluid dynamics stuff but sadly I’ve forgotten so much of it. The gist of it is that as pipe diameter decreases, flow velocity increases and pressure decreases.
As is, I’d think an injector is effectively a pipe diameter reduction, so flow velocity through the injector would increase. When the injector is closed, the high fluid velocity may cause fluid impact issues. I’d think it’s much like when you turn off a tap in an old house. As such flow velocity through an injector may need to be within a given range to avoid damage. It may be that the ECU uses fuel pump duty cycle to reduce fuel pressure which reduces flow velocity to keep the fluid velocity within a given range. Injector duty cycle is used to control the amount of fuel getting into the combustion cylinder.
It’s a bit of speculation on my part as I’ve not digested all that
@07GTS has posted but I’ll get there, one day
Poiseuille’s was another smart Cooke who defined flow rate. Flow rate is proportional to the 4th power of the pipe radius and inversely proportional to fluid viscosity and pipe length. Basically as pipe diameter goes up so does flow rate and the longer or thicker the fluid the lower the flow rate.
Still don’t quite fathom how lowering pump pressure increases flow rate... doesn’t quite marry up to simple science.
In any case it really sounds like the whole shebang is a balance between fuel pump capacity (specs), fuel pipe size and injector size but the duty cycle of the pump and injector is fiddled so things work with some longevity within the desired operating range and power output one desires.
So much more to learn
