Injector duty cycle

[htrdbmr]

I have a 383 with a mini-ram, and the injector bpw at 3500 is 9.2 ms or so, and at the same time it's going extremely lean-22.45 on WB afm. The fuel pressure is steady at 45 or so. I know I'm not making enough hp to exceed the capacity of my 30 lb injectors, is it possible the injectors are shutting down due to too great a duty cycle? The motor seems to fall off a cliff from 3000 to 3500. If it can struggle past that range, it pulls strong from 3500 to 5800. in that range the bpw is 8.2 ms or so. The o2 sensors are not on the same side, NB on drivers side, WB on pass. side. I'm using Tuner Pro RT, all the data looks right except for this condition. I've been chasing this for a long time, and any help/suggestions would be very much appreciated.

[sturgillbd]

A datalog along with engine specs, your bin file and what ecm you are using would be a big step for someone to help you.

Brian

[steveo]

your assumption that it's going extremely lean may be a bad one?

consider that a gigantic series of misfires of some kind will show up as really lean on a wideband (your wideband probably maxes at 22:1 or something, it's probably reading pure air).

your ignition could be breaking up in a certain range or something, or something else might be completely messed up, hell you could have some kind of mechanical issue going on too

it makes no sense the injectors would fail to fuel mid-range then suddenly start fueling again at high rpm. you'd have to have an insanely large spike in volumetric efficiency in that 3000-3500rpm range -- engines generally move more air and hence require more fuel as RPM rises.

[htrdbmr]

your assumption that it's going extremely lean may be a bad one?

consider that a gigantic series of misfires of some kind will show up as really lean on a wideband (your wideband probably maxes at 22:1 or something, it's probably reading pure air).

your ignition could be breaking up in a certain range or something, or something else might be completely messed up, hell you could have some kind of mechanical issue going on too

it makes no sense the injectors would fail to fuel mid-range then suddenly start fueling again at high rpm. you'd have to have an insanely large spike in volumetric efficiency in that 3000-3500rpm range -- engines generally move more air and hence require more fuel as RPM rises.

Thanks for the reply, I need all the help I can get. Prior to installing the WB, I assumed the lean condition because the motor had a "lean cough" when it was stumbling.
At first I thought it was ignition too. I replaced the dist. module, no help. I bought a new distributor (small cap hei), no help. Along the way I tried different coils, no help. I don't think it's an ignition problem. I had thought maybe there was some sort of weird reversion issue with the mini ram, but then it would seem like that or an ignition problem would result in a rich condition, not lean.
I agree, it seems like a mechanical issue is shutting off the injectors in that rpm band, but I cannot find it. Operation is fine in all other areas. I'll post more information when I have it, I'd value your opinion.

[steveo]

but then it would seem like that or an ignition problem would result in a rich condition, not lean.

not according to an oxygen sensor, as a misfired stroke pumps pretty fresh air into the exhaust, ignition problems read lean

[htrdbmr]

not according to an oxygen sensor, as a misfired stroke pumps pretty fresh air into the exhaust, ignition problems read lean

Now I understand, no ignition means no combustion, so no oxygen is consumed. My head was thinking since the bpw was high, too much fuel would be in the exhaust, causing rich condition...duh I bet a spark plug in the tail pipe would be cool (if I could get it to spark)
So now I have to find something that is cutting out ignition.
I went for a walk to clear my head. Ignition can't be failing completely, because the motor continues to run, it's just not making power. I don't see that there is any knock retard in that range, spark scatter inside the cap? (term from back in the day)

[htrdbmr]

A datalog along with engine specs, your bin file and what ecm you are using would be a big step for someone to help you.

Brian

Thank you for your reply,I'll try to do some runs this weekend. I'm using a -727 ecm from a '91 vette, SAUJP v5. As stated the motor is a 383, TPIS mini ram, 224/230 @ .050 cam .510 lift. 700r4 w/3.64 rear