Fuel pressure steady but lean on dyno??

[95 GA/TA]

I just got back from the dyno and i am running lean at about 5200rpm and up.I had installed 60lb injectors so im guessing that its time for a fuel pump upgrade.I have the racetronix with hot wire kit.I watched the pressure gauge in the car as it was on the dyno,i would climp to about 49-50 psi and then stop, it never dropped any but on the dyno graph wideband it was going lean.The fuel pressure is set at 46psi with the vaccum line off.The 50 psi at wot is the gauge in the car with the vaccum line on.I made over 540rwhp on a mustang dyno so im guessing that i need a dual setup but just wanted to be sure.The injector duty cycle was at 70%.Any help or info appreciated.

[Injuneer]

Are you running a 2-bar tune? Who did it?

[95 GA/TA]

1 bar tune,base tune was internet tune.It was on the dyno at a local shop being touched up.

[Injuneer]

Working backwards....

540rwHP through an M6 = 540/0.87 = 620 flywheel HP

620fwHP x 0.55 BSFC = 342 #/HR fuel = 42.7 #/HR per injector

Allowing for 15% bypass to keep the FPR from going full open, 342 / 0.85 = 402 #/HR fuel pump required

402 #/HR / 6 #/Gal = 66.94 Gal/HR x 3.78 = 253 LPH

That would indicate you may be on the ragged edge with the Racetronix pump..... BUT you say your fuel pressure is not dropping. If the engine was using more fuel than the pump could produce, the pressure should start to drop as the fuel pressure regulator opens all the way up. You said the pressure isn't dropping.

As a cross-check to the above numbers, the injectors would be capable of flowing 64.3 #/HR at 50psi (assuming they were flow rated at 43.5psi - is this the correct pressure rating for your injectors?). The calculation indicates 42.7 #/HR flow per injector = 73% duty cycle. You may be running a bit less than an 0.55 #/HR/HP BSFC (closer to 0.525), if you were only at 70% DC. So the calculations would seem to be close to correct, but showing a slightly higher fuel demand than your actual tune. Might be indicating the tune is lean.

Which 255 LPH Walbro did you get, the standard pressure or the high pressure? Since you are trying to run 50psi at the rail, the standard pressure pump might not be flowing 255LPH. But the high pressure pump should be capable of that flow. What did your system voltage look like during the pull? Was there any evidence system voltage was falling off? The wiring kit helps you avoid problems with voltage, but if the system voltage drops, the fuel pump will still suffer.

I'm not sure how accurate a tune you are going to get running a 1-bar tune. Its always a mystery to me how they fuel the engine on boost using a 1-bar tune. I'm not a "blower" expert though, so I'll defer to the experts on that part.

[95 GA/TA]

Thanks man, i agree that it appears i am just on the edge of lean.i believe my afr was about 12.0-12.2 so i was lean at 5200-5500.I believe it is the high out put pump for racetronix but i am not 100%for sure.I have researched and found that they are good for about 500-550rwhp.The injectors are rated at 43.5psi.As for the voltage drop i havent checked that yet but it would be smart too.I have a massive fan setup that really pulls some power and it may be hurting me.I did make a effort to watch the pressure though and it climbed with boost up to 49 or 50 and then seemed to just stop.I believe that i am gonna look into Lonnies dual pump setup and methanol injection kit.I knew it would be close to running out as ive seen some make more and some less with the same fuel pump.I guess its the luck of the draw.I will check that voltage though.I asked the tuner about the 1 bar,he said he had tuned them before with no problems so i guess its ok.I was kinda wondering about that too.He has tuned it many times before and always ran well and made good power.Thanks and im always open for any advice or suggestions.