6l80e pulling rpms down rolling to a stop

[Niemer]

I'm having this strange issue where the trans will pull the engine RPM below 500 as I'm coming to a stop, then right before I stop it feels like something lets go and the RPM returns to normal idle. It almost feels like the converter is locked then unlocks right before the car stops. It doesn't happen all the time, it only seems to happen if I decelerate fairly quickly, if I take a long time to slow down it doesn't seem to happen. I haven't been able to get a log of it because it seems that every time I plug my computer in it doesn't happen. I'm wondering if anyone can look at my tune and see something, G8 GT, TVS1900, stock cam, converter, and trans. I used BlueCat's spreadsheet to make all the changes to shift speeds and TCC lock speeds.

[Niemer]

I was able to get a log of it this morning, it happens at the very end. You can see the RPM go down to 429 around frame 4100 or so. The converter slip seems to be too low for the speed of the car but as much as I can tell it should be fully unlocked in 4th once I go below 24 MPH. You can see the RPMs jump back up to the high 600s once I make it to a stop.

[realcanuk]

Are you sure its related to the trans ? Try raising your idle airflow in the low rpm areas and see if that changes it at all.

[Niemer]

I guess I don't know that it is related to the trans. This all started after I installed the blower and had to make a bunch of changes to the trans to drop the shift points down until I get bigger injectors, so I assumed it was the trans. Could you point me in the right direction for the tables to look at/change? I haven't done any idle tuning, but am reading through the Gen3 how to in hopes of gleaming some info from it.

[Niemer]

Is the Airflow Final Minimum table under the Idle/Airflow tab the one I want to look at changing?

[realcanuk]

Is the Airflow Final Minimum table under the Idle/Airflow tab the one I want to look at changing?

Yes. Search and read about it. There is a procedure for tuning it.

[Niemer]

I put new injectors in so I went back to my original trans tune with higher shift points and the issue seemed to have disappeared. IDK, odd.

[Niemer]

realcanuk, I saw your post here about this issue. It wasn't the solution for the identical issue I was having. CT Downshift is enabled in both tunes, still not sure what fixed it for me.

[realcanuk]

I believe that if the 3-2 and 2-1 downshifts are a little bit higher, this torque management won't have any effect because the trans will "drag" the engine along. I have the 2-1 set at 1 mph because I want the car to stay in 2nd unless I come to a complete stop.

[OldFartC6]

I believe that if the 3-2 and 2-1 downshifts are a little bit higher, this torque management won't have any effect because the trans will "drag" the engine along. I have the 2-1 set at 1 mph because I want the car to stay in 2nd unless I come to a complete stop.

Setting the 2-1 at 1 mph is a good idea. I didn't think of doing that.

Thanks or the idea!