Originally Posted by aidandj
was the one who had issues. He is also running a returnless.
It probably isn't a big deal with the fpr close to the rail, but you need a fuel pressure sensor to be sure.
You need a fuel pressure sensor and you need to look at it with something high-enough resolution to see the pulses. A gauge is worthless, something that logs at the speed of the MS3 (~ 16 hz, IIRC) will show what looks like random noise around the shape that the fuel pressure curve is supposed to be, and with an oscilloscope you can see the injectors open.
FWIW, this is what the fuel pressure looked like with a Walbro pump, stainless lines, non-return system, id1000s, AEM FPR, manifold referenced, and using an FM fuel rail. The the small factory on-rail damper is installed and the big on-fender damper is deleted. It's the white line in the third graph:
Note that there was no obvious drivability problem in the car, the only reason I know there were 10-15 psi fuel pressure swings is because of the sensor I had installed. Does a return-based system have these same swings? I don't know, I haven't measured one, and AFAIK
neither has anybody else on mt.net.
I installed a Radium damper and it completely eliminated the pressure variance.