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Indo-Canuck-Yankee
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Discussion Starter #1
I've got a rail mounted Mallory 4212 AFPR and I noticed recently that my vacuum was a couple of psi low and my fuel pressure was right around 40 psi at idle. It would increase linearly under boost, but was not dropping below 40 psi when decelerating or idling. I tested the vacuum port on the AFPR and sure enough, it was leaking vacuum. Ordered a rebuild kit for the AFPR, but have a nice OEM regulator that I can drop in for the meantime. Is there really any kind of flow difference between the 2 FPRs since they're both rail mounted anyway?
 

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...Is there really any kind of flow difference between the 2 FPRs since they're both rail mounted anyway?
I know the Kirban is, the supply & return ports are slightly larger.
1987-1990 1991 1992 1993 Ford Mustang GT 4.6 5.0 Shelby Cobra BILLET ALUMINUM ADJUSTABLE FUEL PRESSURE REGULATOR #5005

This adjustable fuel regulator is totally adjustable from 30-100 psi. It has a larger feed and return fittings internally for 30% more fuel flow, which reduces fuel restriction of the fuel regulator. If necessary, the regulator can easily be rebuilt as we stock the diaphragms separately.
 

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The regulator port is usually the smallest point in any fuel system. Out of curiosity, what fuel pump are you running now? OEM regulator will have no issues with a 255lph pump.
 

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Indo-Canuck-Yankee
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Discussion Starter #4
The regulator port is usually the smallest point in any fuel system. Out of curiosity, what fuel pump are you running now? OEM regulator will have no issues with a 255lph pump.
I think I have a Holley 190 lph pump installed. I have an Aeromotive 340 Stealth in a box here, but haven't gotten around to installing it yet. Not sure about how to cleanly and reliably upgrade the wiring as is suggested for the higher output pump, yet.

I installed the stock regulator on the rail (with great difficulty due to the access being horrible with a Flowzilla manifold in close proximity). Pressure under vacuum was in the low 30s, even high 20s once the engine was warmed up. At what point do you question how low the fuel pressure is? Once I replaced the fuel filter with one of Canton Racing's CM Filter units, the pressure dropped even more. We're talking about 28-29 psi at idle, less when decelerating. Pressure does increase under boost, to the low 40s, but would this be a good argument for installing an AFPR?

Friends want to go drag racing tonight for test and tune, but not sure this is acceptable. Injectors are Siemens-Deka 80 lb/hr units.
 

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My tuner recommended a stock regulator on my combo, which put 500hp to the wheels. I'm running stock lines, rails and filter with a 340lph pump and 42# injectors
 

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I have a stock fuel system with a walbro 450 running e85. LOL stock pickup, stock lines, stock rails, and stock regulator with SD 80's. Works just fine
 

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I think I have a Holley 190 lph pump installed. I have an Aeromotive 340 Stealth in a box here, but haven't gotten around to installing it yet. Not sure about how to cleanly and reliably upgrade the wiring as is suggested for the higher output pump, yet.

I installed the stock regulator on the rail (with great difficulty due to the access being horrible with a Flowzilla manifold in close proximity). Pressure under vacuum was in the low 30s, even high 20s once the engine was warmed up. At what point do you question how low the fuel pressure is? Once I replaced the fuel filter with one of Canton Racing's CM Filter units, the pressure dropped even more. We're talking about 28-29 psi at idle, less when decelerating. Pressure does increase under boost, to the low 40s, but would this be a good argument for installing an AFPR?

Friends want to go drag racing tonight for test and tune, but not sure this is acceptable. Injectors are Siemens-Deka 80 lb/hr units.
do not be concerned with rail pressure so much

tip pressure is the concern

aim for 38-41psi tip pressure.........=rail pressure-manifold

you will need some math
 

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Indo-Canuck-Yankee
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Discussion Starter #8
do not be concerned with rail pressure so much

tip pressure is the concern

aim for 38-41psi tip pressure.........=rail pressure-manifold

you will need some math
I did not end up running at the track due to the fuel concerns, although I did go the track simply to celebrate my friend's birthday. The event motivated me to drop the tank and sort this out, once and for all - well, for a while.

The current setup is probably right at the ragged edge of not being adequate.

  • Stock tank
  • Aeromotive 11140 340 lph pump
  • Stock lines
  • Canton filter
  • Stock Fox rails
  • Aeromotive 13103 AFPR
Researching options, I came across this article which details an Aeromotive design using stock components that supposedly supports 700 hp. Since I cannot afford to run an A1000 complete system and I don't expect my power expectations to exceed 700 hp (but am very likely above 600 hp, which appears to be above what the stock lines will support), this plan makes sense.

Basically, the only thing that needs to change would be:

  • Run fuel pump hanger with larger output diameter
  • New feed line (have some -6AN PTFE lined stuff in the garage)
  • Adapters and fittings as needed for new feed line from hanger to rail and return
Uncertain about the wiring aspects of the upgraded pump. I'd really like to avoid having to run a lengthy 10 gauge power line from the front of the car to the back. I have a hefty car stereo amplifier setup that is already on a 200A circuit breaker and powering some relays in the rear already... was thinking of piggybacking on that instead. I believe it's 2 gauge wire from the circuit breaker. Maybe?
 

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....Uncertain about the wiring aspects of the upgraded pump. I'd really like to avoid having to run a lengthy 10 gauge power line from the front of the car to the back. I have a hefty car stereo amplifier setup that is already on a 200A circuit breaker and powering some relays in the rear already... was thinking of piggybacking on that instead. I believe it's 2 gauge wire from the circuit breaker. Maybe?
You probably don't need it. My Walbro 255 draws 7.5A @ 13.5V at 40 psi. Not a problem for existing 14AWG.
Walbro gives a better description.
Fuel Pump: GSS340
The Walbro high output in-tank electric fuel pumps are available in flow ratings of 255 liters of fuel per hour. These particular pumps flow significantly more fuel at higher pressure. For example, at 80 PSI the standard 255 lph pump will flow around 132 liters (35 gallons) per hour. At that same 80 PSI the equivalent HP (high pressure) fuel pump will flow over 210 liters (50 gallons) per hour.

BTW, with an AFPR you can raise the fuel pressure to 50psi or more.
 

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Indo-Canuck-Yankee
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Discussion Starter #10
According to Aeromotive's published charts, the 340 Stealth draws 13A @ 40 psi, 15A @ 60 psi, and 19A @ 90 psi. 14AWG rated at 60*C ambient is good for about 17A - while I don't intend to push the pump that hard, the pump manufacturer has made it very clear that upgraded wiring is required. I'm planning to run some Turnigy 200*C silicone jacketed 12AWG or 10AWG, should be good for a hot 20-30A, easy. Planning to run a relay to bypass the long stock 14AWG feed and use the feed to drive the relay instead. Real PITA to upgrade the pump wiring in a clean fashion...
 

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Indo-Canuck-Yankee
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Discussion Starter #12
Ok, so what is the point of upgrading all the wiring to a better, lower resistance state when you've still got to contend with the relatively miniscule 14-16 AWG leads from the inside of the hat to the pump itself? Sure, the leads are only about 6-8" long, but they really should be upgraded. I was all about doing this until I realized that it's difficult to find the snap lock style quick disconnect 0.250" female terminals in 12-10 AWG. I can find them in 14-16 AWG max, no more for some reason. Probably not looking the right places.

In any case, I've upgraded the fuel pump wiring by adding an extra relay triggered via the old fuel pump relay output and powered by a massive 0 gauge welding cable directly from the battery via a 150A circuit breaker. The new relay has a 30A fuse on it, should the Aeromotive pump develop serious electrical issues. I reused the existing 4-pin male/female connector for the fuel pump passthrough wiring between the trunk and to the external tank area. I was able to do this because I had several of these connector pigtails from some EEC-V scrounging I had done more recently. Many of the '96+ Ford cars use these connectors, but are setup using heavier 12 AWG wire. I repurposed these pre-crimped 12 AWG leads and reused the silicone passthrough plug with wider diameter lead holes as well. The end result is that the entire setup looks totally factory - however the fuel pump wiring is much heavier gauge, higher quality jacketing, and relay fed for lower voltage drop.

Fingers crossed.
 

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I've got a rail mounted Mallory 4212 AFPR and I noticed recently that my vacuum was a couple of psi low and my fuel pressure was right around 40 psi at idle. It would increase linearly under boost, but was not dropping below 40 psi when decelerating or idling. I tested the vacuum port on the AFPR and sure enough, it was leaking vacuum. Ordered a rebuild kit for the AFPR, but have a nice OEM regulator that I can drop in for the meantime. Is there really any kind of flow difference between the 2 FPRs since they're both rail mounted anyway?
No, unless something else is screwed up...,Waste of $$ IMHO.
 

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Indo-Canuck-Yankee
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Discussion Starter #14
No, unless something else is screwed up...,Waste of $$ IMHO.
I'd agree with you if I hadn't heard that you need to increase base fuel pressure for a forced induction high output engine. That being said, I have no idea how much to increase my base pressure by.
 

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Indo-Canuck-Yankee
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Discussion Starter #16 (Edited)
the regulator increases/decreases base pressure as needed

why its called what its called
The base pressure dillhole!

Well who's the dillhole now... the OEM baffle has broken off and is loose in my tank. Are there any fuel tank upgrades that accept the stock style pump hanger available for the Fox Mustang?
 

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Indo-Canuck-Yankee
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Discussion Starter #18
If your injectors are able to support your horsepower level at a fuel pressure of 40psi there is no reason to raise the base fuel pressure just because you have forced induction.
Great, thanks for that response. I'm using Siemens-Deka 80 lb/hr injectors which I believe should support my power levels even if kept static at 40 psi.
 

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The base pressure dillhole!

Well who's the dillhole now... the OEM baffle has broken off and is loose in my tank. Are there any fuel tank upgrades that accept the stock style pump hanger available for the Fox Mustang?

base..........leave it alone, let the reg do its job


run this tank

Complete Late Model Mustang Cell, SA110A
 

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Indo-Canuck-Yankee
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Discussion Starter #20 (Edited)
Ha, now that is one spendy tank setup!

I spoke with Glenn's Performance today for quite a while about the tank setup. Apparently, the OEM Fox tank is not a bad one with its internal baffle intact. Their suggestion was to simply replace the stock tank with a new one, although the new ones offered by Spectra Premium for example, have thinner gauge steel walls than the stock Ford units. For this reason, I'm thinking of having my stock tank dipped and the baffle welded back on by Performance Radiator, which seems to specialize in these types of things. Interestingly, dipping and rewelding the baffle will cost $125, whereas a new Spectra Premium tank costs about $100.

Also, I was told that the stock regulator, while it will work for a while, doesn't have a very tough diaphragm material and will eventually have an issue after cycling through boost. How is Kirban for a stock replacement AFPR?
 
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