RPM drops coasting

[ns158sl]

I have been fighting this for a a few weeks now. Seems no matter what I do doesnt really help, and/or just amplifies the issue. I have tried a few different avenues. Ive tried throttle follower, VSS RPM setpoint, prop airflow, integral airflow, all 3 spark adapt tables, trans downshift speeds, then i took a deep dive at VTT.

I can't seem to get the coastdown Idle nailed. It always overshoots and will be 200 rpm below commanded, which then drives adapts nuts and oscillates. Im sure i can figure out Proportional eventually, but I am trying to prevent the overshoot first. Stock Cal has its 0'd for prop so idk where to keep going. I am starting to think the trans is binding from 2-1 and dragging the rpm down but i highly doubt thats the cause.

[Alvin]

Almost always.. A idle dip like this is caused by going to rich as it returns to idle. I saw a couple returns to idle with your AFR 13.3 which is rich enough to cause exactly this.

Even if the MAF is well tuned you might run into this because a lot of this situation is referenced by VVE first. Have you purposefully failed the MAF and flushed out the VVE?

[ns158sl]

I did awhile ago, but I've made changes since, especially when the calculates. I'll double check when I get home, here I was thinking lean lol, but it goes lean probably from the trims pulling it down.

[IN10SS]

I think I may be having a similar issue with my new build. Good luck with the resolution and please post how this worked out. Thanks!

[ns158sl]

So there a few things going on. Alvin was onto the fueling. Problem was, I am still figuring out why. One thing I noticed tonight is my timing is almost 20 degrees lower in the idle coast compared to the HO. That sends the fueling nuts and then the trims try to compensate both ways, and too slow, lol. I did get a crash course on integral airflow. There is definitely something that needs to be addressed also. But first would be fuel and timing, theeen start adjusting integral, if needed.

[GHuggins]

Usually when timing changes fueling that much injection timing is off. It looks like you might be running a modified version of one of my earlier boosted tables? If so it's too retarded. Target 570 as the max value then taper it down easily from there. Also possibly running a GPI cam from the looks of the VE spikes? They always seem to cause those. I will say that once you have the fueling figured out you can usually fine tune the idle with the throttle stop and airflow settings. You can also dial back the actual spark values being pulled and then play with coastdown spark if you like. It all works together. You really need to put the torque model back to stock and only correct the idle area for now. It will indeed help to control idle more, but if not shaped right it can hurt more than it helps. You can log and plug in delivered torque, but you need to include the offset created by the air models into it. 4th gens aren't as dire to have it perfect. It will most definitely help to get reported into the 20's to 40's either way for throttle and timing control.

[ns158sl]

I used the killer EOIT calculator so I assume Im closeish. No that timing table was from a 6.2 denali. Figured Id start there being the new engine was 6.2 bore and LS3 heads. The VT tables were an average of L92 and LS7 being it is a 10.8 to 1 Cr, 405 Cu In.

I "fixed" the fueling like Alvin stated and that helped a bunch. It still drags the RPM too much coming to a stop. I also corrected the Idle timing tables. So at this point I have almost eliminated Integral for High RPM (-RPM) on the coastdown for the -32, -64 areas, and that helped also. At this point I will start dialing in the Coast Decrement, being that helped a shitload. Only other avenue would be to adjust the Integral coast limits and put back the coastdown back closer to stock, but one thing at a time. Thank you everyone. Someday this thing will be driveable enough for the wife ahhaha.

[IN10SS]

Thanks for the update. Glad you're getting closer. Some knowledgeable people offering good strategies. I wish I could contribute to the solution besides offering a cheering section!