? About "fuel pressure across injectors"

[itzl0l]

I've been data logging a bit, base tune (waiting on the arrival of prp software) and havee a question about the "fuel pressure across injectors" pid. I have heard differing opinions as to what this should read under idle, cruising and wot.

Mine idles about 38-40psi but doesn't rise with boost as I've read it should.. Actually it drops and fpdc goes to 100.

Some say this pid should rise with boost... Others say it should always be around 39-40... Still others say it should idle around 20 (base minus manifold vac).. I understand what a mech gauge should say... But what about the sct pid?

It's like the actual frps isn't seeing or responding to boost and vac (I have verified the vacuum and boost source going to sensor is good).. And as such fuel pressure isn't rising like it should and as a result the fpdc goes through the roof

Possible bad frps?

03 cobra.. 2.3 whipple @ 17.
2400 maf
Stock pumps with bap/wire upgrade.. Pprv still in tank (I've never had the hesitation)
No cats.

Afr mid 11s but oddly when the fuel pressure pid goes south and the fpdc goes up the car actually goes rich... In the mid upper 10s.

 

[2004silvercobra]

Mine idles around 38-40 but goes up around 50+ at Wot

Sent from my Galaxy Nexus using Tapatalk 2

 

[03Steve]

It depends on what you ask the EEC to do. You can change fuel pressure across the injectors in a couple of manners with the calibration.

Want to know how far your FPDAI is off from the commanded value? Log 'Fuel Pressure Error'.

 

[itzl0l]

so when looking at that (fuel pressure drop across inj) is it what the ECU *thinks* the fp is or is it what the ecu is commanding?

I'll see if i can get a log of the fuel pressure error later. As well as voltage to the pumps. Battery voltage at wot never drops below 13.05.

Again...really just a base tune until i actually dig into it, but seeing the fuel pressure drop and the fpdc spike, followed by the car going into the 10's afr peaked my interest. Just thinking about possible mechanical issues...like bad frps or something in tank... dont wanna chase my tail when i start tuning

 

[LeKiD]

If you hit 1.0 FPDC you need more pump . Its not a good thing to have the fuel pressure below 36-37psi.

Mine is around 40 at idle and still up to full boost. FPDC is at .3 at idle and .78 at wot .