tnx for the reply that cleared it up for me, ill seach for a voltage boster and see how that works.

 

1: Have you tried changing the fuel filter?

2: You have to get larger fuel injectors as they are too small.

Re'

 

Ok i got the larger injectors installed (LS1 28#'s for now) and i have NOT changed the fuel filter yet. Ill do that as soon as it stops raining.

IS their a way i can boost the fuel pumps performance temporarely, some one mentioned larger wires, and some ones i taked to said run a wire straight from the battery to the pump harness on the rear.

Can you guys explain a little more on how to do this?

 

An LS1 28# injector is the same size as a stock LT1 injector, when you run the LS1 injector in the 43.5psi LT1 fuel system. You haven't gained anything, unless you boosted the fuel pressure to the 58psi level the LS1 uses. You could have done the same thing with the stock injectors and turned them into 28 #/HR injectors.

I will assume you are reading your injector DC from DataMaster. From my experience, the DC reported in DM is higher than actual. Appears they calculate it by dividing the injector BASE pulse width by the time available for 2 revs of the crank. While that would be correct if the BASE pulse width is the same as the actual pulse width, I'm not so sure they are correct. With a good tune, the stock injectors would be supporting about 425 flywheel HP at 100% DC (which you don't want to run them at).

If you are making appreciably more than 425 HP, you need larger injectors. You also need a larger (or healthier) fuel pump. If the pressure is dropping, it isn't because the injectors "are staying open too long". The injectors are staying open as long as they need to, to support the HP (assuming the tune is correct). The fuel pump is not able to supply adequate fuel flow to meet the requirements of the engine.

Poor voltage at the fuel pump would cause it to flow poorly. Have you checked the voltage at the pump? Have you ever checked your system voltage at 6,000rpm? Is it maintaining close to 13V under those conditions? If the voltage is falling off, the pump will lose capacity.

 

Tnx Injuneer, you caught something that i would have never, thanks for really paying attention and thinking about my problem!

You know i got these freaking injectors at a f-body performace shop, i told them i need to get bigger injectors and they sold me the LS1 ones
I have to find a LT1 tuner, Some of these guys really know their sh*t about LS* engines but are in the dark when it comes to the LT1.

As far as me reading the Duty Cycle im doing it from auto tap, it show the pulse width (witch was 22.5 and 22.3 at 6025 rpms) and from another post of your i calculated the 112% DC. I know it isnt going to be 100% correct but with that and my plugs being all white after a WOT run i am pretty sure i am running lean up top. NOW if understand correctly this could be do to the fuel pump not keeping the presure at those RPM's and the computer trying to correct that buy opening the injectors longer. I dont think i am really near the 400+ HP mark, but i will find out to day on the dyno. If im not i will just chalk the injectors up to general mantinance

I will check my voltage to the pump (is at the conector on the rear ok?) and check the voltage at high rpms (At the battery?) If that is fine then i will buy a performance fuel pump and see where i am with that.

Gawd i hope i get this fixed soon!

 

The PCM can't try and compensate for the low fuel flow/pressure at WOT (PE mode). It is ignoring the feedback from the O2 sensors at that point. The pulse width is based on the standard fuel calculation, dividing the MAF air flow by the target A/F ratio to get mass fuel flow, then multiplying that result by the long term fuel correction for Cell 15 (assuming the PCM was adding fuel in that Cell).

Your AutoTap scan will tell you what the "system voltage is". To measure the voltage at the fuel pump, get as close to the pump as you possibly can. In most cases, that's is the harness connector over the rear axle.