Quote Originally Posted by joecar View Post
You need to do this:

- find out wheather your fuel pressure regulator is vacuum-referenced or not...
if it is, it will be on the fuel rail(s) and have a vacuum hose attached to it;

- find out your fuel pressure:
vacuum-referenced: pull the vac hose and measure it,
non-referenced: measure it;
do you have any [electric/electronic] device that alters pressure...?

- find out injector rated flowrate:
if not stock, what is their rated flowrate and rated pressure...?
Joe,

Isn't equal to the pump pressure? (I mean the rail pressure), so if the pump is a stock one, very easy to know its pressure.

What about depending on efilive scan tool, I found the following (in PIDs):

DESCRIPTION PARAMETER
Fuel Rail Pressure SAE.FRP_C
Fuel Rail Pressure (Gauge) SAE.FRP
Fuel Rail Pressure Relative To Manifold Vacuum SAE.FRP_B

Another question, let's say the stock fuel pump gives 58 psig. Is it possible GM designers will rate engine's injectors at lower than that, so we need to correct it when we start tuning??????