Injector Delta Pressure - is not really pressure but math?

[CTSVNZ]

Heres a good one. I have read everywhere the injector delta pressure is rail pressure less boost pressure. makes sense.
But I am running a LSA with no factory fuel pressure sensor (ie 0 pressure shown in HPT). All I have is a Fuel Pressure Requested (that never moves - set at 65 psi approx), yet the Delta pressure moves around and drops under boost.
So one must assume the Delta pressure is a calculation of injector math against requested pressure - and is not actually attached to any actual real time pressure readings at all.
Any thoughts on this...

[blindsquirrel]

In the ones without a physical fuel pressure sensor, the math assumes a fixed 58psi versus manifold pressure to calculate the Delta.

[blindsquirrel]

Oh, and, it's still just math even where there is a physical sensor.

[hjtrbo]

See here...
Fuel pressure sensor doubts (hptuners.com)

[TheMechanic]

See here...
Fuel pressure sensor doubts (hptuners.com)

Something kind of dinged in my head about that. Tell me what you think. The stock sensor is vertical to the fuel line without increase or decrease in line diameter. My theory is that it is getting a venturi effect, so as the flow increases the pressure at the sensor will decrease being less accurate. It would be intresting to plot the difference between the pressure seen at the rail and the pressure at the sensor as actual volume/flow changes across the "tee" at the sensor.
Might be barking up the wrong tree but something to think about. Maybe a correctable error fix.

[blindsquirrel]

I would probably want to measure, with an external device, actual sensor voltage. Then compare with the scan tool data. If they diverge anywhere, then it's processed data shown in the scan tool and not reality. I hate when they do that shit.

[CTSVNZ]

Makes the most sense. Thanks

[smokeshow]

Absent the pressure sensor, or with a sensor that has not passed the relevant diagnostics, the fuel pressure in the injector delta pressure calculation will assume the 'default' value under 'Desired Fuel Pressure'. However, manifold pressure will still remain active in the delta pressure calculation.

[lxlaw]

Absent the pressure sensor, or with a sensor that has not passed the relevant diagnostics, the fuel pressure in the injector delta pressure calculation will assume the 'default' value under 'Desired Fuel Pressure'. However, manifold pressure will still remain active in the delta pressure calculation.

i have the FP sensor hooked up and it still goes off of requested not actual. I wonder if there is a way for it to get it to run off actual? It would be perfect. Goes to 74 psi under WOT, but requested in still 58, it looks like ill have to calculate low/high flow settings and set the pressure as close as i can get, run it a little rich. Or not run boost reference at all, set at a static 58 or 65 and run it like that. Only way ive been able to get it right. Or run a static flow number on injectors where this adjustment has no effect on fueling and set the flow rate at 58 psi or 400kpa