? about converting to return style fuel system

[Joe Lynch]

I already have a return style regulator and '03 pumps and have been running with an eFPC for a year on 100-150 shot with good results. But it isn't perfect.

I can make the computer speed the pump up to go on the regulator control at 50 psi, but I can't keep it there during the run. The computer interferes.

Here is what I propose doing. Run a 30 amp fused 12 ga hot wire from the junction box to a spdt relay (30 amp) in the trunk. Connect the pole of the relay to the pump hot wire, use the normally closed contact for the normal fuel pump circuit from the FPDM and inertia switch. Connect the normally open contact to the new hot wire from the battery.

Energize the relay coil when the nitrous system arming switch is on. Then the full 12 volt will be sent to the pump, it will go to full speed, the regulator takes over, and the fuel system runs at 50 psi instead of 39 psi.

I can correct both open loop and closed loop mixture for the new fuel pressure with the MAFterburner Plus (or SCT 4 program chip).

The only problem I see with this is that the stock normal fuel pump circuit is now dead ended (open) at the pump due to the new relay. Will the FPDM send a pump monitor signal back to the PCM that will result in unusual engine control problems or a SES light?

One of my problems is that I don't understand how the FPDM works. I can't tell what it will do from reading the emissions control book from Ford.

Any comments are greatly appreciated.

Joe

[Ed Clark]

Joe,

Do you have the SCT software yet?

I haven't done any nitrous systems like yours before, but I've done returnless/return conversions and even a hybrid type setup and using nothing more than the SCT software could get almost full control of fuel pressure using either the software or the FPR.

Ed

[Joe Lynch]

Ed--No, I'm waiting on the flasher. I have a TwEECer right now and can't access any of the fuel pressure tables. But I may want to go to a constant voltage signal to my '03 Cobra pump and use the mechanical regulator I already have when the nitrous system is armed.

Do you have any idea what action the PCM will take if the fuel pump is no longer wired into the FPDM? I know there is some feedback to the PCM from the FPDM but it is not clear what action the computer takes if "trouble" is detected at the fuel pump. Any ideas?

Thanks,
Joe

[Ed Clark]

Joe,

There are settings in the SCT software to fix the voltage the pump speed. So yes, you can probably do what you want.

If you give me your computer code I'll ensure it's in there for your car.

Ed

[Joe Lynch]

ZMR2

Thanks, Ed.

Joe