I was wondering what drainback fitting I should use in my AEM fuel pressure regulator? I bought it used and it didn't come with instructions. I'll be running a walbro 255 and probably stock rail pressure. around 300whp on 550cc injectors. Should I use the big, medium or small opening fitting? Thanks for any help.

Nate

 

use at least the medium with the 255lph .
something about the smaller one with more pressure from the bigger pumps causes diaphram flutter and missfires, mine did that and drove me nutts for a while until i got on the phone with AEM , he told to me switch that and worked like a charm since.

 

ok, thanks. The biggest one is in there now. Not sure if I should swap it out to the medium or not..

 

youll prob be fine with it , thos ebigger fittings have to do with fuel pressure thue the fpr, and the smaller the fitting the more you will need to turn the set screw in to lower the pressure from what i remember and it causes the diaphram to flutter becuase it tries to clamp down on it too much or something , i forget how to explain it

 

If it's working fine, leave it in there.
using the largest one with my fpr, I'm also runing a holley 255lph intank pump.

 

Haven't put it on yet so not sure how it works. I'll probably just try the big one. thx guys