Restrictor in Prochgr FMU Vac Line, Why?
 

I have the Aeromotive A1000 fuel pump and regulator on my 5# procharged 454 MAG MPI.

I recently installed a mechanical gauge at the FMU and notice a pulsation, or oscillation, of the fuel pressure at idle. The extent of variance is only 1 or 2 psi, at the most. It is a fairly quick oscillation of pressure.

I have read that procharger (and some aftermarket FMU mfgs) sometimes suggest the use of a .018" dia restrictor oriffice in the vacuum line leading to the FMU. I do not have one in my vacuum / boost signal line.

Could the purpose of this restrictor be to act as a pneumatic damper and smooth out the flutter I'm seeing, or does the restrictor act to buffer (slow) the rate of fuel pressure adjustment.

Your response is appreciated.

anyone?

Comon' there are a lot of smart people out there. Someone must know.....

the restrictor is to slow the rate of pressure increase once boost is acheived

I had the same set up and never saw any flucation of pressure. If 1-2 at idle I wouldn't think it's much too worry about as long as fuel pressure at higher rpm is correct.

We've installed a restrictor jet in the MAP sensor line on Procharger and turbo drag cars with stand alone aftermarket ECU's to smooth the signal so it would keep the fuel and timing table corrections stable. We've also installed restrictor jets into the boost gauge lines on late model turbo diesel trucks to keep the gauge from jumping around. I'd think you're getting both results............dampen the pulsations and that will stabilize and smooth out the fuel psi adjustment at the FMU.

Good Information.