I'm running a little lean with my new setup, my injector BPW is showing 10-11 past 6k rpm in TunerPro and I'm wondering does this get divided by 2 since it is batchfire? Basically anything over 10 at 6k is 100% dutycycle. I'm running code 59 for my setup with 60lbs injectors and afr usually stays in the 11.8 range but after a new pulley change with more boost I'm getting up to 12.7 past 6k. Not sure if my 255lph pump is at its limit or the injectors are to small and I need to pump up the fp to bring the BPW down some. Though you would think 60lbs injectors would support this engine no problem

So I got some help on code59.org with my question and looks like I'm running out of injector and my duty cycle has been maxed out. I suspect I hit the limit of my fuel pump. Once I get my car all put back together after this cam change, I have a new auto meter fuel pressure gauge to setup and hope to see what's going on.

When i went thru this exercise i was told batch fire you multiply the calculated duty cycle % by 2.

In my case my log shows 8.91 pulsewidth at 5775 rpm. Thats 42.88% by the calculators online but since you fire twice its actually twice that or 85.76. I dont know if i believe that but maybe its right, for me that seems high running 115 lb injectors and only 15 psi boost.
11.7-11.8 air fuel so tune is spot on where i wanted it

What did your car trap again? I would think 60's would support 600whp fairly easily, and that should put you closer to 130-135 mph traps if 3500-3600 lbs raceweight

No doubt that you are out of fuel pump. The fuel pressure is dropping off. Here is a quick calc using 60#/hr injectors:

60 #/hr * 8 cyls = 480 #/hr total fuel flow at 100% DC.

Fuel weighs about 6#/gallon, so 480 / 6 = 80 gals/hr.

Convert to quarts, which is a tad less then a liter:

80 gals/hr * 4 = 320 quarts/hour.

Then google to convert to liters: 302 L/Hr.

So yes, no more fuel. Time for a double pumper. Also, that 255 lph rating is usually at 13.8 volts and 43.5 psi fuel pressure. As the pressure increases the flow drops off.

Instead of getting a gauge it is better to get a 0 - 100 psi pressure sensor and log it. Tough enough watching where one is going then have time to look at a gauge.

Injector DC% conversion (RPM & Injector PW based, this is for the common double fire set up):

6000 RPM / 60 = 100 RPS = 100 RPS

1/100 = .010 or 10 msec between injector firings

If the injector PW is 8 msec: 8 / 10 = .80, then * 100 = 80% DC

RBob.

Single pump should support 550 whp. Maybe 500 in a higher bsfc boost motor. Depending on fuel pressure ofcourse. Your combo should be capable of maxing it out but i dont recall your traps being 500 whp level? Is the pump getting full voltage?

That's pretty much how I'm told how it works and seems to make sense since I'm maxed PBW at 6k or so and my AF/R starts to rise after that point. What don't make sense is the car is only trapping 114mph which is pretty low for maxing out the injectors though I'm reving it a lot higher now after this mini ram intake swap. I never did put on a fuel pressure gauge and drove around with it before I tore it apart, my guess is the 255lph is not supporting the mods. I have a walbro 400lph coming, hopefully I can make that fit if this is the problem...

Honestly the car should be trapping 125mph or higher with 12psi at 6k, something is up even though the wb02 is showing a nice AFR line up until that point. Plugs look fine too

No I haven't looked at the voltage at the pump, one of those need to do projects. I do have a hotwire kit from racetronics I could put in but I like to see how the stock wires hold up, it's been good to me up until this point.

Thanks Rob for the calculations, I run 44psi with the line off but I'm not sure how the boost affects the fp regulator. Looks like the pump change will have to be a go

The larger the pump the more current it pulls. The more current it pulls the greater the voltage loss through the wiring, which means that the pump doesn't pump as much fuel.

At 44 psi line off and 12 psi of boost, the fuel pressure will (should) rise to 56 psi. It is a 1:1 ratio to maintain the same pressure differential across the injector. Which in turn has the injector staying at the same flow rate.

RBob.

Just curious about this pressure sensor thing. Could you post some details about this? Like what kind of sensor and /or where to get one. And by logging it do you mean data logging as in Tuner Pro? Can it be done with TP?

Sorry for the thread jack...

I have gone to using Honeywell pressure sensors. They are well built and have an automotive temperature range, which is important for stuff that goes under the hood. This is the part number 0 - 100 psi sensor:

MLH100PGB06A

It has a male 1/8" NPT fitting and a 5V power supply (pick up from MAP or TPS). Use a 1/8" NPT to -4 adapter, then a piece of -4 Teflon lined hose to connect to pressure fitting.

For data logging I use the EBL products which makes it easy. Otherwise, I think the AutoProm has logging capabilities.

RBob.