Rolling Idle Surge TCC Unlocked - L83

[WS6FirebirdTA00]

All,

So this really isn't a major issue as the TCC is nearly locked all the time, but on the way out in the AM with a cold transmission and the TCC lock delayed as a result of being cold I get some rolling idle flare.

Tune and log attached, also a screen shot of the issue area.

I had upped the rolling idle and it seems more stable, but still hunts. I went back to stock and tweaked the idle external load and the stock table only made it worse (had a weird spike at 1300 RPM).

From what I see there is either some spark control playing into it or DFCO. Right before the dip the spark is stable, then it dips. Then the recovery spark and thus RPM right after.

Any suggestions? I am not sure what else would be causing the crazy spark swings. I did tweak the rolling idle in that area from 600 (stock) up to 900 now and it was more stable. This way it seems more like a dip then recovery. Before it was a dip then a surge.

[WS6FirebirdTA00]

Well, tried to bump up rolling idle and put the idle desired RPM in and max I ever saw was 896 RPM. It maxed by 15 MPH and does not correlate to the table at all.

[Higgs Boson]

off throttle on a downhill?

[WS6FirebirdTA00]

Mainly, yes. Some other areas were flat, but I lost speed too fast to really see.

I was thinking maybe going in and out of DFCO, but with unlocked TCC it should disable below 1400.

[WS6FirebirdTA00]

Another odd thing, the fuel trims rail at +39.x% when the RPM is stable. Then when the spark changes they go back to about -0.2% and swing back to +39.

I only saw a few times where I saw the trims go +25 like they do on DFCO exit, but it was not consistent with all surges doing that.

TCC unlock high STFT.PNG

Nothing is consistent other than the spark. I can only assume the desired idle speed is too low for where it wants to idle, it pulls timing to try to get there, pulls too much and then adds it back to prevent undershoot. I sent a note to support to check on the rolling idle tables to see why it basically does nothing. At one point rolling idle command is 800 and I am commanding under 700, then the next it commands 896 when I command 1000. I thought if I could get it to command 1000 it would be happy there.

As I coast and get below 50 MPH in 8th gear it will settle itself out at about 940 RPM. I don't know if it finally stabilized there or hits a new value in a table that allows it to stabilize. Really hard to test that as losing speed too quick doesn't give enough time to capture anything. I thought this was a key speed because in the stock table at 51 MPH rolling idle went up to 800 RPM from 600 RPM.