100% IDC, bigger inj. or injection?

[blcknspo0ln]

If anyone ends up searching this, my IDC's went from 100% to 69%, ceteris paribus.; I jumped from Denso 660's to FIc 950s.

 

[kahl23]

The biggest restriction in the system is actually in the return line. The higher flowing system is trying to shove too much fuel back through the return line, so the pressure you set at the regulator is actually lower than it is at the injectors. Until you fix this, something like raising the fuel pressure at the regulator won't do much. The good news is you can just run some some ss line or large diameter hard brake line to fix the problem.

For the front end of the system: http://www.dsmtuners.com/forums/showthread.php?t=209428

I was thinking about that, but on the other hand, who cares if a lot of fuel is just sitting in the fuel rail? Generally at WOT, most of the fuel is getting used up that goes into the fuel rail. And it's not like the fuel pump is pumping at the same PSI the entire time its being driven around town. I undertand that the fuel needs to return back to the fuel tank, but I wonder how "necessary" it is to upgrade the fuel return line for most "normal" applications.

In case someone searches this, here's the deal on the return line:

The thing is that the fuel doesn't just sit in the fuel rail, it goes out the injectors. Don't forget that fluid under pressure follows the path of least resistance. In this case, that means that it goes out through the open injector. The end result is that the ECU believes the fuel is at 37 psi (for example) at the injectors while it's actually at 42 psi or higher. Because of this, more fuel is delivered to the cylinder than is needed (or wanted). You end up with a rich mixture.

Now get out there and widen those return lines!