SpeedracerRX7

Ok I went single almost 3 years ago now and I have never been able to get the fuel setup to work correctly. The problem is that when the the car begins to boost the fuel pressure drops. I do have a 1 to 1 FPR and I have T-ed the line from my boost controller to the FPR to make sure it is reading the correct pressure. I have tested the FPR with just the pumps on and not the car using a pneumatic hand pump and the FPR raises the fuel pressure accordingly. I have even powered my pumps directly from the battery so as to rule out the relays.

I am running what you see in my signature with 2 Denso Supra fuel pumps. I am running through my stock fuel lines and using the venting solid line for a return back to the tank. The two fuel pumps were originally run seperately with individual fuel filters. Due to some problems I switched over to running both -8an lines to a Y with a -10an filter and then back through a Y to two -8an lines then running throught the stock hard lines. It then comes out around the firewall and through my fuel rails seperately and then goes into either side of the FPR. The return then returns to the tank via an -8an and stock hardline.

OK the only thing I can narrow a problem down to is that somewhere I have a restriction in one or both of my supply lines. The diagram attached is a rough approximation of the fuel setup. If you have any questions feel free to PM me.

Busted7

I see nothing wrong with the diagram. I would look at wireing and pumps first. Try disconnecting one pump at a time and make sure there both working. Are you running two relays with power direct to battery and turned on by computer? Kinda sounds like your only running on one pump! If one pump is running it can back feed at the y's and reduce pressure becouse you have no check valves. Good luck!

SpeedracerRX7

That is the first thing that I thought I should check too. For this reason I have changed both pumps out with 2 others that I have had and the problem persisted. I am running 2 seperate relays, one for each pump, that are both sharing a trigger wire. In my troubleshooting process I have used a wire off the battery to both trigger my relays and also to directly power each pump through switches that I had installed. I am thinking of trying to install some checkvalves but that will still cause an issue if one pump is dropping out because the overall pressure would probably drop.

I am thinking of buying enough of the aeroquip hose to completely run from my filter to the fuel rail to eliminate the chance that I have a restriction in my stock hardlines. I hate to do this as it would probably cost me $150-$200 for the hose and the hassle.

Does anybody think that it may be the FPR? Is there anyway it can be this? It is the only thing in the entire fuel system that I haven't changed. I may in the near future borrow one that I know is working off ShawnK's car that I know works. It is funny because I built his car with him and we are having no problems when it comes to fuel pressure.

arghx

iTrader: (3)

Do you REALLY need two fuel pumps? 500R... that's a little bigger than a GT35 right? Have you considered simplifying your system, not because a dual pump isn't better for fuel flow, but because it may not be necessary and it's just more stuff to fail/cost you money?

I have run 21 psi on a T04S (smaller than a 500R, yes, but not a tiny turbo) with just a hotwired Supra TT pump (no resistor relay, just big gauge wire triggered through a relay by the stock circuit opening relay) and base fuel pressure of 40psi set on my Aeromotive FPR tapped into a nipple on the UIM. That's gotta be 400-420rwhp with a big street port, maybe more, with no fuel pressure issues. How much power is this making/going to be making? You can also do a single Supra TT pump with a Kenne Belle Boost-A-Pump, which will flow 600whp on a piston engine and probably 500 on a rotary. I just use 6AN line which is close to the size of the stock fuel line, everything is in series (no Y splitter), new stock replacement fuel filter.

Now I know you would rather just get the setup you have working, but is that complexity really necessary? I bet if you ran one Supra TT pump in the stock location with 10 gauge wire going to it (with new ground) you would flow enough for 420-450. You don't even need the Y splitter either, yes I know it's superior in some way but most street cars don't HAVE to have it. And if you really are using a stock FPR (that was unclear to me from your post), ditch it.


My system goes like this (this is on an FC, but it's not that different really) 1 Supra pump in tank --> rubber hose connects to hardline in tank --> 6AN line to fuel filter (it's in the engine bay on an FC) --> 6AN clamped to primary rail barb --> KG secondary rail with 6AN fittings --> Aeromotive FPR --> 6AN clamped to stock fuel return hardline

For wiring, I cut the stock pump wire right near the tank and used it to trigger a relay which pulls bigger gauge wire directly from the battery to the pump, ensuring that the fuel pump ALWAYS sees full battery voltage with almost 0 voltage drop, so around 14. I took the unusual step of running that wire right into the gas tank, but I don't think that's necessary.

Azcamel

iTrader: (1)

i having the same problem. i cant get any more fuel up top (7k above at WOT) . my afr is high 11 (like 11.8-11.9) and with a light jump to 12.2 at 8k. i tried to richen up as much as possible, the tuner said that he added more via PFC controller and it really didn't help much to the top to rich it up. im running dual supra pump, direct wire to the battery so its getting around 14 volts, then to the hard line, and 6an to the rail/FPR. i also have 550 primary and 1600 secondary. Its was tuned on a mustang dyno reading 400rwhp and around 355FPTq, according to the tuner it should be 440-450rwhp on a dynojet for comprasion. he is thinking i have a clog fuel filter, or maybe the hard line is not big enough. do you guys think the OEM hard line is the problem? i was hoping for 500whp on a dynojet or 450 on a mustang dyno, i rather not redo the hard line for a 6an or 8an if i can help it, i rather just leave the numbers where its at.
BTW the FPR is at 42psi, and boost is at 1bar.

mods are
large stg 4 street port
GT42
550primary 16002nd
2supra pump hard wired
aeromotive FPR
rail is rated for 1khp

am i missing anything?

Turblown

iTrader: (12)

Could also be a problem with one of the pumps. I would switch to one big pump personally. What is the fuel pressure when this lean condition happens?

arghx

iTrader: (3)

^^ dude you are probably running out of injector. 550/1600 is undersized for a GT42. Either go with 850 primaries (at least) or install a third fuel rail and wire them in with the secondary injectors. On the dyno, do you see your fuel pressure dropping up top? If the fuel pressure isn't dropping it's probably not a problem with the fuel pumps, and I really doubt it's the hardlines. What is the peak fuel duty cycle reported by the commander? And I'd also like to know what injector settings he's using (lag and transition) but I don't expect you to have that information.

Is he tuning it with the Commander handheld unit or the datalogit laptop software?

Azcamel

iTrader: (1)

tuning with commander handheld unit. dont knwo about the lag or transition. he did not metion any pressuer drop, i think the peak duty was in the low to mid 80 ( think i saw 84).
will i just have to buy retainer clip for the 850 primary? anything else i need beside that and a tune?

arghx

iTrader: (3)

^ You need a tuner who has the proper equipment to tune your vehicle, which is the Datalogit laptop software. Installing big secondary injectors requires adjustment of settings which are not accessible by the handheld controller. Otherwise you may have hesitations and injector staging problems. It's also really hard to tune the trailing ignition split.

Have you considered AZRotaryRockets? http://www.azrotaryrockets.com/ they know their ****, or so I hear.

Bacon

iTrader: (12)

Your seeing fuel pressure drop @ the FPR’s gauge correct?
One thing I have seen MANY friends and customer who plumbed their own fuel system the fittings going into the FPR, you HAVE to use Radiused Pump Fittings, if your using regular length threads to -8 the threads on going into the FPR are way to long and the hole inside the FPR where these fittings goes to is small and if its blocked only 50% you will get the issue you are having. The Radiused Pump Fittings have shorter threads to prevent this problem

http://www.jegs.com/i/JEGS/555/100163/10002/-1


I know above is hard to explain, Cmartinp28 had this problem @ a dyno tune with Steve Kahn, he didn’t believe me until I took off the 4 Allen screws holding the top of his fpr and he saw th threads blocking the holes that come into the FPR

Your setup IS fine, I would definitely either swap FPR’s or set up a fuel press gauge other than the one in the FPR….

You have more than enough fuel to keep pressure up @ higher rpms, look @ whats giving you the readings, i.e- the pressure gauge, its placement, fuel flow through the FPR….

Bacon

iTrader: (12)

My fuel syst is 2 Walboro’sm feeding 2 areomotive filters, running through the stock hardlines (1 for each pump, and the 3rd as return) into kg primary and secondary rails 850/1600 into areomotive fpr… both pumps coming right off the battery (mounted in the hatch)

When I first plumbed it I didn’t get full fuel press till after 1 min and would get press drop on the high end. Was beating my head against the wall thinking I had a bad FPR, anyone who has taken one apart knows all that’s in side that top hat of the FPR is a ball and spring, and diaphragm to increase pressure with boost, theres nothing to really go wrong besides a tear in the diaphragm. (this is how I saw the threads of the fittings going in blocking the holes into the top of the FPR)

If you have pressure, its not the pumps running out of steam, one pump is almost enough to keep pressure for the amount of fuel your drinking,

The filter, yea it might be, depends if your running the paper 10 micron, or metal screen 100 micron one the smaller the micros although better filtering, decrease flow. I run the paper. If you are premixing the premix builds up in the filter, maybe part of the testing (if you don’t take a look @ the FPR’s fittings first ill be mad lol) pull out the fuel filter and make a run, see if you get any pressure drop

Bacon

iTrader: (12)

the hole in question, its easy to bottom out a fitting thus keeping pressure in the supply lines, but not flowing through the regulator (the fpr pressure gauge gets is pressure from inside the cap of the fpr, not the line pressure coming in) so you might have the pressure but cant see it.... lol

SpeedracerRX7

Though that would not be LOL funny for me that could defninately be it. I'll pull that and check that this weekend. Thanks for the help. I think mine are just regular pipe thread adaptors. I don't know if I have ever looked at my AFR on my wideband because I was just so concerned about the reading I was seeing on my guage. By the way it is and Aereomotive 1:1 FPR with a defi sending unit in the guage port.

Bacon

iTrader: (12)

If you have easy access to the top of the fpr, don’t pressurize the fuel system.

Loosen the top set screw (the one that adjusts the fuel pressure), then loosen the 4 Allen screws holding the cap on. From there you will be able to see into the top of the fpr and see how deep the fittings thread in. if you can see the threads down through the fpr your going to need the Radiused fittings.

Sorry for being the crazy poster, I’ve seen this happen to at least 12 FD owners and it drove me crazy, cant help but share the useless knowledge.