I am setting the pressure on my return style system in my 2012 GT500 and I notice that the fuel pressure that I am logging is 8-10 psi higher than the pressure shown on the fore fuel pressure gauge that is in the rail 5" away from the factory sensor. Can someone help me out with why the sensors are so far off? I have my injector data setup for 50 psi base pressure. but had to add 8-12% or so total to get my STFT near zero in the maf curve of my PMAS.
For example when I have the vac line off the regulator the scanner is reading 58/59 psi and the gauge is reading 50 psi. When I connect the line back up to the regulator the scanner drops to 51-53 but the mechanical gauge on the rail is around 42-45. I have always just set it by the mechanical gauge, I changed the fuel lines around and spent some time tonight messing with it and noticed just how far off they were. If I drop the pressure where the scanner reads 50 psi then my fuel trims are adding like 9-10% on top of the adjustments I already made in the MAF curve. When its set from the mechanical gauge it bounces from -1 to +3.
I think I figured it out. I left the stock fuel pressure sensor still hooked up to the vac as I just pulled it off the regulator. I believe it is showing the delta between the pressure in the manifold and the rail pressure. When I am out driving it bounces around between 49-51. no matter what boost I am pushing.
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