Gary Z

Recorded data from my stock fuel system showed a significant pressure droop at WOT. I need larger injectors and was dissatisfied with the performance of the stock system so I installed a Racetronix pump and wiring harness. I had expected that fuel rail pressure would be more constant but I am surprised to find virtually no improvement. Average fuel pressure at WOT is approximately two psi higher but the droop has increased. Graphs showing performance of the original and Racetronix systems are attached.

It is not my intent to bash the Racetronix system which I believe to be well engineered. The geroter-type pump is undoubtedly superior to the original vane-type pump and the Racetronix wiring harness will supply increased current with a lower voltage drop than the original wiring. I am however still not happy with my fuel system. I now think that a better pump is merely a band-aid on a poorly designed system. I also think I won’t get the performance I want without going to a full-return system with the regulator at the fuel rail. Bummer.

Jake@EPP

If there was no improvement on the two fuel systems then there is a issue somewhere else. If it was on the vehicle in your sig, the stock setup should have been fine. The racetronix or even a plain 255lph should have been rock solid. Being a return less system is a MAJOR fault, but even a plugged up fuel filter would cause a large inconsistent drop like shown.

Gary Z

Jake, thanks for your input. Yes, it is the car in my sig. The fuel filter was replaced a few months ago and my tank was immaculate inside (turquoise) so I don't think that's the problem. The two in-tank socks were discolored (brown) but not clogged. There are no kinks or leaks in my fuel lines.

Jake@EPP

The socks are usualy discolored soon after installing, it means there doing there job. Another possibility is the pump is going bad, i would also check voltage back there.

MIGHTYMOUSE

iTrader: (59)

have you considered that your fuel pressure regulator may be the issue?

Gary Z

Pump voltage is not the problem. The wiring to the new pump is much better than the original wiring. I understand the importance of a good ground connection for the Racetronix wiring and I exposed bare metal under the relay-mount/ground lug. I think my graphs show normal performance for the original and Racetronix systems. I would very much like to see data that shows otherwise.

Gary Z

Yes, but I think it is performing normally. I think it just doesn't work very well. I didn't disassemble it but others have said it is just an orifice.

Racetronix

iTrader: (2)

This is a FPR location issue. No matter how good the pump is, it can not compensate for line pressure drop given the factory regulator's location. You can use a BAP which will create a pressure rise that can offset the line pressure drop but a FM FPR is a better approach in this case.

If you add a FM FPR you will see that that Racetronix system can support much more HP esp. with a pump booster.

Gary Z

Racetronix, thanks for confirming my suspicions. As I indicated, I am impressed by the Racetronix kit but have been surprised to learn how poor the stock fuel system is. Before I investigated, I had assumed that normal pressure at the injectors was always close to 58 psi. Clearly this ideal is not necessary. I am going to go ahead and install my matched Ford red-tops but I will use something like 55 psi when calculating a new injector table.

Thanks to all, Gary

oange ss

iTrader: (50)

i also have a Racetronix P-N-P kit, my fuel pressure is 58 psi with light throttle and 60 psi at idle, WOT gets down to 53-55 psi..just got done dropping the tank and checking for loose connections, with no negative results..I'm not using the hotwire kit....just adding info to the thread, from your data, my data and Racetronix's input it sounds normal considering the fuel system design

Doc

iTrader: (9)

I just went thru this ordeal and might have some info that could help. I am monitoring FP with an Autometer FPSU @ the rail w/ EFI Live. I noticed a huge drop like you and others have mentioned. I logged batt volts and found out that at the drop off point I was going down to ~10vdc. I rebuilt the alternator and the problem went away. Hope this helps.

SPRAYED 01

iTrader: (22)

I to logged voltage at the pump at wot and idle. I found with racetronix pnp with wireing harness,idle would be at 61psi, and full throttle would go to 55psi everytime. Voltage at idle was 13.8 and full throttle was about the same. Seemed to work just like the stock system.

oange ss

iTrader: (50)

i upgraded my charging wires to 4 guage and installed a 160 amp alt, my voltage never drops below 13.8 regardless of conditions...

BrianC98Z28

iTrader: (11)

where did you get the 160amp alt??

oange ss

iTrader: (50)

Ebay, forgot the name of the company, Power Alternators or Mr Alternator somrthing like that...do a google search, there are quite a few companies to buy from...