Calibated base idle airflow again and now it's 18-28% lower?

[AdsoYo]

After getting the new LS3 swap running the first thing I did tune-wise was fire up HPTuners and set the base idle airflow. I did it in cool dry air, somewhere in the mid to high 50's. A few nights ago it was down around 30 degrees so I took the car to work, planning on running the RussK idle config while it was nice and cold out and I'd be able to populate the 46 degree column in the table. Well I let the car idle up to operating temp and the whole table filled with numbers that were much smaller than before. Up to the 111F column the numbers were 18% smaller and above the 111F column they were 28% smaller. The car idles okay with a very slight oscillating surge after a cold start. I know that usually means this table isn't dialed in so I'm going to run the new numbers. I just want to know how could there be such a difference if I didn't change anything?

Here's the original table

oldbaseidle.png

Here's the new table

newbaseidle.png

Here's the comparison table

comparebaseidle.png

[AdsoYo]

Ran the idle config again tonight and got numbers closer to the original. What variable am I missing here? Why the flip flop?

[AdsoYo]

Loaded up the new larger numbers because it idles better with them. Had another cold night so ran the idle config again. Again it spat out smaller numbers.

So if I run big numbers, it gives me small numbers and if I run small numbers, it gives me big numbers. It idles great with the big numbers so I'm sticking with those. Still would like to know why hptuners is doing this.

[bk2life]

What variable am I missing here?

change to g/s on the chart. youre currenlty logging pounds per hour.
that wont help, but the chart is so off im having ahard time understanding

[bk2life]

i opened my tune and grabbed both for your understanding of the differences.

20230302_150816.jpg
20230302_150825.jpg

[bbowerman]

Have you dialed in the maf curve or the ve with a wideband or narrowbands yet? That needs to be done before trying to dial in the braf. Are you doing the ltit+stit method? I prefer the dynamic airflow method but the maf and ve must be dialed in first. Also you say it's swapped but I need some more info to give better advice. Is it an aftermarket harness or is it swapped into a factory ls vehicle? What intake and Throttle body are you using?

[bbowerman]

I see you said russk now that's ltit vs stit. That does work but only with stock throttle bodies in my experience. Dynamic is a better way to do it imo but if you have a stock TB then I've had decent luck with the stit+ltit way. On an aftermarket TB you dial in your fueling completely then do a datalog when its completely cooled down. Setup a histogram logging dynamic airflow just like the stit+ltit histogram is setup and put those numbers in. You also need to have an iac effective area correction histogram setup. I can upload some pics of the setup for that. But if you have an oem throttle body that table doesn't need modification.

[Tunercharged]

The closed loop adjustments have to be monitored when setting up the Idle air. If Maf or Sd is way off then the ecu may throw the AFR way off trying to correct for that and the swing back can be pretty far so the initial idle air will no longer be enough or be too much. Once idling steady enough set the AFR for Maf and Sd correctly and then adjust idle air flow again, it should be easier to find a good level the second or third time around.

[Alvin]

LTIT and STIT will hardly ever backup day to day like fuel trims will.


The IAC is really the slow response in idle control. As long as it is range timing will control it just fine. If I can I like to shoot for a -0.5 gram/sec error in LTIT + STIT (so purposefully a touch high)