Need help with 383 TBI

[Hellbilly]

I adjusted the whole spark map, brought down the injector size to give you more room in your VE table. Should get it more to drink with the injector size being programmed smaller. As such I roughed in a VE table that is smoother than a plateau of 100%. I also disabled the EGR since the AFR Enforcers do not have EGR passageways to feed the valve.

Test carefully while listening for audible pinging.

Wow, thanks. Yes, distributor is set at 5*. I hadn't smoothed anything out yet, that bin was just where I ended at yesterday, by changing a few cells at a time till I got to where it would go down the road. I also forgot what you said about lying for injector flow and had just added 15% to the factory tables, and smoothed out a little... wasn't actually planning on needing anymore than that when I went out.
I noticed you also changed the AE, I was going to ask if I should do something with that. And also what is the reason for changing the AFR stoich?
want to make sure I understand the reason behind changes, so I can get better at this.

[Fast355]

Wow, thanks. Yes, distributor is set at 5*. I hadn't smoothed anything out yet, that bin was just where I ended at yesterday, by changing a few cells at a time till I got to where it would go down the road. I also forgot what you said about lying for injector flow and had just added 15% to the factory tables, and smoothed out a little... wasn't actually planning on needing anymore than that when I went out.
I noticed you also changed the AE, I was going to ask if I should do something with that. And also what is the reason for changing the AFR stoich?
want to make sure I understand the reason behind changes, so I can get better at this.

Change stoich because almost all fuel you will find now has 10% ethanol. Just corrects the fueling from the alcohol content being added to the fuel. I did bump up the AE modestly to get it some more to drink when you open the throttle. The AE is all pulsewidth based and proportional to airflow. If you have more airflow you need more fuel.

I decreased your injector flow rate in the tune because I noticed the INT and BLM rising in areas you already had the VE table at 100%. The injectors were still showing the pulsewidth and duty cycle to be fairly low. I reshaped the VE tables to try to get them more in line with what I feel the VE probably is on your engine given its specs. Adjust from there.

I am sure it will probably run, how good I cannot say since its more or less a startup tune I would flash into my Autoprom and modify from there.. I also raised the idle just a bit to keep the cam happier.

If it is globally rich, increase the injector flow rate in the tune. If it is globally lean decrease it. Once you get the BLM and INT in the 128 or less ball park, you can fine tune the VE table from there. My typical BLM target is 124. Keep it slightly rich and let the computer pull fuel as it sees fit. Prevents the fuel curve from having random lean hiccups.

Not sure if you noticed that I also brought your open loop air/fuel ratio table more inline with what it needs to be. GM programmed them to command 16:1 during warmup and they tend to run very lean set that way.

[Hellbilly]

Ok, cool. I haven't had time to mess with it yet... hopefully this evening. I am concerned that I'm not going to here knock over my exhaust though. It's pretty loud with true dual, headers and flowmaster 40s. The last time I messed with it though, I had exhaust popping in some areas. Would that indicate a need for more or less timing? At the times it happened I still had enough fuel. I found out the knock sensor I put in was for a manual transmission if that makes any difference (besides throwing a code) I'm going to order the right one and a wide band on Friday.

[Fast355]

Ok, cool. I haven't had time to mess with it yet... hopefully this evening. I am concerned that I'm not going to here knock over my exhaust though. It's pretty loud with true dual, headers and flowmaster 40s. The last time I messed with it though, I had exhaust popping in some areas. Would that indicate a need for more or less timing? At the times it happened I still had enough fuel. I found out the knock sensor I put in was for a manual transmission if that makes any difference (besides throwing a code) I'm going to order the right one and a wide band on Friday.

The manual trans knock sensor is the same as the older one. It was used on the trucks that had a seperate ESC module as well as the Vortec 350s. Make sure you torque it to 15 ft/lbs. The torque value is critical for it to work accurately.

Every engine setup is different but if it pings a little at part throttle it won't typically destroy anything. Detonation at higher rpm and WOT is what kills things. Stay out of the throttle until you get it dialed in better, have a knock sensor and a wideband. If your narrowband is in the 880-930 mv range under load its not really lean anyway.

There are plenty of SBCs in service without knock sensors. Just have to be a little more conservative on the timing.

[Hellbilly]

Little update: I got the knock sensor replaced this week and got the truck running good enough that I drove it to work a few days. Had a few issues I was having trouble figuring out. But, Friday, my MAP sensor decided to quit working, so I put the new one back on. This one seems to read about 5-10KPA different than the old one did, but now I'm chasing non-engine related issues. Rear axle seal leaked into the drum, so I gotta get that fixed.

Some of the issues I was having: When coming to a stop, it gets to about 1000RPM and kinda hangs out there, making it feel like the engine is trying to push through the brakes. Until you get to below 5MPH and it switches to idle timing. Would the fix for this be less timing at 1000RPM or raise the max MPH for idle timing?

The other issue is, at idle, I've noticed that the IAC is going all the way to zero and hangs out there till I accelerate again. I've sat in the driveway at idle and played with timing and VE but, it seems like no matter what, it idles 750-775RPM, IAC at 0, and 5 degrees advance. What am I missing?

If it makes any difference, I've had Power Enrichment and DFCO turned off while trying to get VE dialed in. I can get a log to upload today, if you want but I have a feeling everything is going to be a little off again, because of this MAP sensor reading a little different.

Also, I got a wideband, but don't have everything to install it yet. Have to double check PCM connectors, but I don't think I have a wire on the pin needed to log AFR, so I'm gonna have to buy some pins. Or I guess I could steal one from the EGR solenoid wires

[Fast355]

Little update: I got the knock sensor replaced this week and got the truck running good enough that I drove it to work a few days. Had a few issues I was having trouble figuring out. But, Friday, my MAP sensor decided to quit working, so I put the new one back on. This one seems to read about 5-10KPA different than the old one did, but now I'm chasing non-engine related issues. Rear axle seal leaked into the drum, so I gotta get that fixed.

Some of the issues I was having: When coming to a stop, it gets to about 1000RPM and kinda hangs out there, making it feel like the engine is trying to push through the brakes. Until you get to below 5MPH and it switches to idle timing. Would the fix for this be less timing at 1000RPM or raise the max MPH for idle timing?

The other issue is, at idle, I've noticed that the IAC is going all the way to zero and hangs out there till I accelerate again. I've sat in the driveway at idle and played with timing and VE but, it seems like no matter what, it idles 750-775RPM, IAC at 0, and 5 degrees advance. What am I missing?

If it makes any difference, I've had Power Enrichment and DFCO turned off while trying to get VE dialed in. I can get a log to upload today, if you want but I have a feeling everything is going to be a little off again, because of this MAP sensor reading a little different.

Also, I got a wideband, but don't have everything to install it yet. Have to double check PCM connectors, but I don't think I have a wire on the pin needed to log AFR, so I'm gonna have to buy some pins. Or I guess I could steal one from the EGR solenoid wires

Have you adjusted the Minimum Air Rate screw on the throttle body? If you have not, I suspect a possible vacuum leak. The IAC counts should be low at idle, but not zero. I would say probably 5-15 counts at idle is enough for the PCM to be able to lower the idle as needed.

Less timing will allow the engine to idle lower with the same IAC counts FWIW. Retarding the timing while the engine is decelerating will make it return to idle more quickly.

[Hellbilly]

Have you adjusted the Minimum Air Rate screw on the throttle body? If you have not, I suspect a possible vacuum leak. The IAC counts should be low at idle, but not zero. I would say probably 5-15 counts at idle is enough for the PCM to be able to lower the idle as needed.

Less timing will allow the engine to idle lower with the same IAC counts FWIW. Retarding the timing while the engine is decelerating will make it return to idle more quickly.

Ok, so I finally got brake issues worked out so I could drive the truck. But the ignition timing is making me feel like a complete idiot. I keep adding timing to open throttle table, or taking away were I get knock retard, but I feel like I've added way more to the majority of the table than I should have and it doesn't seem to have any effect on what the truck actually runs at. Except that I noticed after adding a bunch of timing to idle table it revs really high and holds it at initial start up. Once it gets into closed loop it goes back to the normal timing that it always runs at. I know its not going to run the exact numbers that are in the tables, due to coolant bias and whatever other bias's it has, but the tables literally seem to have no effect on closed loop. Is this normal or am I completely missing how to tune ignition on these things? When I tune fuel, I turn off power enrichment, DFCO, EGR ect. and can get it close that way. Do I need to be doing something similar with ignition tuning? the truck is running good enough to drive through town, but has its quirks still, and the timing tables don't look anything like what I think they should. But I can literally sit in the driveway with my Ostrich plugged in and add 5* to the table and nothing changes.

I've looked on here and other places online, looking for a tutorial on ignition tuning and can't find anything that's helped me. I get the idea of the timing shelf before knock occurs, but cant seem to actually get the truck to run more or less timing than what its doing on its own, except at initial start up. I data logged my drive home from work, and I'll add the BIN used. I put the idle advance table you sent me back in to keep it from running at 1200 RPM at start up, but you'll see that I have a lot of timing in the open throttle table, and its not actually running near that advance and its not knock retard taking it out.

I've appreciated you help so far, I'm not looking for someone to do this all for me, I want to learn to do it myself. I'm just not understanding how the PMC is correcting it, I guess. Thanks