I just upgraded to a #14 pulley on my p-600b. when I finished all the work I was doing, I found that my in-line pump had died. I want to upgrade the fuel system but I'm not sure of the way to go. I have been looking at and aeromotive in-line to replace the old one but was wondering if I should change all the line at the same time. New to all this, so I don't know much. What is the purpose of an FMU? I see most people remove them ASAP. Should I remove mine? Me and a buddy do all the work ourselves so it's learn as you go. Any help would be great.

Chris

 

The FMU increases the fuel pressure under boost by restricting the flow through the fuel return line (the same way the stock fuel pressure regulator works). The higher fuel pressure under boost forces more fuel through the injector at the same pulse width, thus avoiding the need to reprogram the PCM. It's a cost effective way to add fuel under boost to go along with the extra air, but it's not an exact tool. Adjusting it basically comes down to making the car run rich and then trimming back the fuel until you're not running too rich. Like I said, not exact, but it works. Compared to the price of 42 lb/hr. fuel injectors, it's not a bad way to go for a stock or mostly stock motor. For the best performance and to keep your air/fuel right where it's supposed to be, you're better off with injectors and a professional tune. Again, like most things, it comes down to the cost factor. For a modified application, you're best to have a professional tune anyway. The FMU can still be a useful device, but it depends on how you go about the tuning.

As far as a custom fuel system goes, when you're talking about higher boost and increased fuel needs, replacing the lines with larger ones eventually becomes a necessity. There are lots of threads on the subject, just search around. You can ditch the FMU and get yourself a set of big injectors, just know that you're going to need some involved tuning to get it all to work right--unless you know what you're doing, you'll likely need professional assistance from a qualified PCM programmer/tuner.

Dave