Originally Posted by MikeR
I have a pressure sensor on my fuel rail and a Zeitronix/Dashdaq to monitor fuel pressure.... mine is adjusted(NW fuel kit) to 62psi and at WOT I see the rail pressure drop to about 48psi while sucking down gas..very interesting to look a the data log of the fuel pressure across a run....
What do your AFR's look like when it drops?
Sounds like you may have a fuel supply issue...the pump isn't keeping up with the demand. The regulator tries to maintain pressure by returning excess fuel back to the tank. When there is no excess, the regulator is closed off and the total volume of fuel is going out the injectors. When the injectors flow more fuel than the pump is supplying, pressure drops.
These constant-power pumps will supply more fuel volume at lower pressures, since it is fighting less against the head pressure. A possible solution (if lean) would be to lower the pressure, and increase injector pulse-width at WOT if possible. Unless there is no more inj pw and they are static, then the solution is more pressure (and possibly bigger pump).
Dropping fuel pressure is not always an issue. When the pressure is high at low-demand conditions, the PCM just dials back inj pw. At WOT, if inj pw is large enough and fuel pressure drops to a level sufficient enough to maintain AFR, then it's ok. However, almost always, there is no safety margin if the need for more fuel (hot day, bad gas, high boost, etc) suddenly arises.