How to lower fuel pressure???

[gallacmic]

Ok so now that I know my erratic fuel pressure was discovered to be because my fuel pressure was to high which was revealed by a live data logger tool which said my fuel trim was -18%. What happened was the computer was trying to lower my fuel pressure by slowing the injector pulses but it would overcompensate and make the car stall and bog. I was able to lower the fuel pressure from 37 psi to about 29 psi which brought the fuel trim down to -8% and the car definitely idles better but not perfect. The problem now is I have lowered the fuel pressure as far as it will go with my adjustable fpr. The screw is as far out as it will go. The vortech fmu is the only thing now in the return line and I guess that this thing has a base pressure of 29 psi just from the size of the holes in it and the little disc the fuel runs into going through. Is there any way to go lower or is my only option now to adjust the duty cycle of the injectors?? 0% is what Im shooting for as that is what the computer is happy with just like it was stock and thats where it idles perfectly. I have a 255hp walbro and 310cc accell's and a 12:1 vortech. If I cant get this to idle right I might as well get a portfueler and put the 310's in the portfueler and the stock 190's in the stock rail. 500cc total I guess.
Thanks for any input or ideas!

[SilvrEclipse]

The computer is not trying to lower fuel pressure, the ECU has no idea what your fuel pressure is, all it knows is that there is to much fuel going into the motor so it decreases pulsewidth to try and compensate. The ECU can only adjust +/- 20% so yes you should be trying to get under about 5%. Remember that after every change you need to reset the ECU by pulling the battery so the computer has to relearn the fuel trims.

The stock injectors are 235cc, what year car do you have so we know your fuel setup? With your 310 injectors you only need 75% of the stock fuel pressure. So I would start at about 34psi. Reset the ECU and see what happens. Drive the car for a couple days and then check the fuel trims.

Also because you are running larger injectors you dont need to run a 12:1 FMU. You probably should be around 8:1 or so. Im betting you will run stupid rich in boost. If you have the money I would highly recommend port fueler or a SFMU at the very least. You can sell you FMU and AFPR to help fund it.

[gallacmic]

I use the 12:1 based on my a/f readings. I tried a 10:1 and under boost the a/f was 12.9 to 13.1 so i put the 12:1 back in and now Im at 11.9 to 12.5 under boost. When I ordered my injectors from cimotorsports they told me the stockers were 190cc. The aftermarket injectors start at 200cc and go up from there.
http://www.cimotorsports.net/motor-s...alon-420a.html
I went back to autozone and had them plug in their live data scanner and I noticed that at idle this time that the throttle position percentage was at 12%. I checked out a bunch of other forums and it seems like every other car varies from 1-10% but never 12% Any idea what the 420a is supposed to be at? On dsmtuners a guy with a gsx said he keeps his at 1% and anything over that causes the same idle symptoms Im having. BTW I tested the map sensor and it passed all tests. Here is the link for the map sensor testing on chrysler maps. My car is a 98 and please explain what the benefit is of a super fmu over using a regular fmu combined with an inline afpr? The only thing I can see is they are one unit that does both tasks at $300
http://easyautodiagnostics.com/chrys...shooting_1.php

[danielsatur]

What about the fuel pump regulator?

[gallacmic]

See my first post. I backed the afpr out as far as it will go and the idle is at about 29 psi.