I want to raise the fuel pressure from 39.15 psi to 45 psi. This would be enought for this 2010 Mustang GT 4.6 3V N/A without changing injectors. I set the (engine, fuel, General) "Pressure Drop Ref from 39.15 to 45 PSI (45/39.15=1.15). Under (fuel Sys, General) "Desired Injector Pressure Drop" I raised the old data 1.15 times (to 46,06 psi) and the same under "Desired Pressure Drop High Load, table data times 1.15, new table data 45.00 up to 80.50). At first I logged the Fuel pressure from the pump with VCM Scanner 2.24 and it is now at 45 psi, like wanted.
BUT: messuring at the fuel rail with an Adapter and fuel pressure gauge shows the old stock 39 psi at the injectors/fuel rail.
What is wrong on my doing? Why is the fuel rail pressure not raising to 45 psi?
Change your Injector Pressure Drop Reference back to stock. That number is the reference pressure that the injector data was calibrated under. That gives the ECU a baseline, if you will, to calculate fueling from. I don't know if that will change your rail readings, but it should be done anyway.
Drop Reference is back to stock 39 psi.
But no changing. The logged fuel pump pressure is at the new 45 Psi but the real messured fuel rail pressure is still at 39 Psi (Sensor Voltage 3.1 V). The fuel system is returnless, there is no pressure regulator, only the fuel pressure sensor. All HP-Tables for fuel pump pressure where changed to the new wanted pressure, but there is no changing at the fuel rail. Even deaktivating of adaptive pump voltage changes nothing. Who can help?
Remember that if you put a gauge on the rail, its giving gauge pressure not absolute pressure. The FRPS is providing absolute pressure (what you'll see in the datalog) but if you put a gauge on the rail that gauge is referenced to atmosphere so it is displaying gauge pressure. On this gauge you should see your target pressure (45 psia) minus one-half the manifold pressure (in in-Hg) when manifold is at vacuum and target pressure plus boost (in psi) when under boost. So if idling and you have a manifold vacuum of 20 in-Hg, the fuel pressure gauge should display 35 psig (45 - 20/2 = 35) and if under 10 psi of boost it should read 55 psig (45 + 10 = 55).
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