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]

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

[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)

[steveo]

still could be fuel, though... don't let me throw you too far off.

a great trick for that kind of thing (finding a spark miss while driving) is to get your inductive timing light, put the probe right near the plug boot of the suspected cylinder, and just point the damn light at your windshield. then go for a drive. if the flashing gets sketchy, you'll know what's up.

you can then track backwards to before the distributor cap to see if it's a distributor/plug wire cutting or the coil?

it's probably not the pickup or your ecm cutting spark, or you'd see your tachometer drop out in that range, wouldn't you? (assuming you have a fairly responsive tach)

a portable oscilloscope is a superior tool to diagnose any of these issues, of course

are you 100%+ sure you don't have a valve hanging up or something?

[buddrow]

Have a look at the fuel and spark maps in that rpm/load range. Also, verify the distributor is set at 0*, the ecm pulls 9* iirc then adds per the cal. I can't see an injector going static at 3500 rpm then clearing up after. Double check that there is no spark knock detected during this hiccup. Does it act up in park, if you rev the engine to 3-3500 or is it only under load?

Buddrow

[htrdbmr]

Did a quick data run today, I saw some knock retard in the areas in question. I disabled knock retard and went out for a while to run some errands, problem persists. Attached are my bin file and logs. If one of you can see something that might be the cause of the problem, I'd appreciate your suggestions

[steveo]

if im using the wrong mask or something don't get me wrong, i'm not experienced with this xdf and really want to help,

..... but has your ve table been sniffing glue?...

[sturgillbd]

I agree with steveo. The VE table has some issues. Your fueling is dropping sharply after 3k rpm. You may be overcoming the VE with PE and that is why it pulls after you get over the hump. How are you adjusting your VE? The datalog you sent is short with little steady driving. See this thread for how to use BLM data to adjust your VE tables: http://www.gearhead-efi.com/Fuel-Injection/showthread.php?1895-Adjusting-VE-Fueling-tables-with-BLM-data-Tutorial! It also describes how to populate your history table with good data so you can adjust the VE table. It is a basic tutorial based on the $0D mask but the same principles apply for all masks.

Attached is a screenshot of the sample count on the extended table with NBO2 data.

[htrdbmr]

if im using the wrong mask or something don't get me wrong, i'm not experienced with this xdf and really want to help,

..... but has your ve table been sniffing glue?...
Wow, that does look bad- I'm glad it's not mine. Seriously, thanks for looking into this but I think you have the wrong dxf or mask. I'm using S_AUJP V5 I'm at work now, so I can't post shots of my VE tables or graphs. I'll try when I get home.

[htrdbmr]

I agree with steveo. The VE table has some issues. Your fueling is dropping sharply after 3k rpm. You may be overcoming the VE with PE and that is why it pulls after you get over the hump. How are you adjusting your VE? The datalog you sent is short with little steady driving. See this thread for how to use BLM data to adjust your VE tables: http://www.gearhead-efi.com/Fuel-Injection/showthread.php?1895-Adjusting-VE-Fueling-tables-with-BLM-data-Tutorial! It also describes how to populate your history table with good data so you can adjust the VE table. It is a basic tutorial based on the $0D mask but the same principles apply for all masks.

Attached is a screenshot of the sample count on the extended table with NBO2 data.Thanks for looking, that run was to try and capture the instances where the system went lean. What's strange is the data points that are missing, from 3000 to 4000 at less than 95 kpa.

[htrdbmr]

I took a closer look at my VE tables this weekend, ( BTW, I am using the extended table, to 6400 rpm) and yes, it does look a little lean. I did richen everything beyond 3000, and took it out for a ride. I did not log it, just went to see if the problem persisted, and it did. It sure feels like ignition, but I can't find it. Nailing it from a stop has no hesitation anywhere, and it will pull until I back off it. I apologize for not staying with you, and again, I appreciate any help you can give me.

[sturgillbd]

I saw some sharp spikes in your VE table. I am working out of state this week and don't have my tuning laptop with me. Ill try to view the datalog again in a virtual machine tomorrow eve since this is a Linux machine. Could you maybe get another datalog driving around? Try to populate the history table while staying out of PE.

[sturgillbd]

Here is a view of your VE table. Notice the spikes down low in RPM. Also notice the fuel dropping off above 3000 RPM.

[htrdbmr]

Pouring rain when I got home last night, couldn't do any logging. Maybe tonite, but now we have a hurricane to think about. Those spikes were a quick and dirty run thru a spreadsheet, no finesse or smoothing.

[steveo]

you are tuning with a spreadsheet already? you need a ballpark ve table and lots of clean logs to do that. i'd reccommend a fresh ve table based on a similar engine. yours is trash.