occasional stalling

tooned Ve then MAf, now tuning idle

having issue with occasional stalling

overall decent but i having a hard time remembering the steps for tuning braf/ltit/stits

can someone provide me a reminder so i can ship this tahoe


cam, CAI, headers, stock truck intake with flex injectors



---only concerned with remembering how to get the airflow portion corrected---

thank you

Attachment 157628
Attachment 157629

You never really come to a stop long enough for me to be able to judge if BRAF is right. It takes a sec for STIT and LTIT to start moving.

The VE doesn't look fully flushed out to me. Do have a wideband? There are areas it will traverse coming back to idle that can be 15% rich but go though it so fast the fuel trims never come off 0. What cam is in it? Using a wideband to get part throttle VE is critical IMHO especially on a GEN 3 with slower to update fuel trims than later gens. It sucks to break all that out for this.. but it can take a 10 reflash tune job down to 3 just to get VE completely right. Getting VE right can solve things like this.

EDIT Oh. tune BRAF to be slightly positive.. .5-1 g/s. SO logging STIT+LTIT will show -0.5 ~ -1 g/s

Undo what you did to the overspeed tables. Be mindful that timing dips can cause the idle to drop.

VE can't be right.

BRAF looks too low for any amount of cam.

Quote:

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Originally Posted by Alvin

You never really come to a stop long enough for me to be able to judge if BRAF is right. It takes a sec for STIT and LTIT to start moving..

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Quote:

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Originally Posted by edcmat-l1

VE can't be right.

BRAF looks too low for any amount of cam.

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for me to remember / learn again, im looking for the info on how to tune the ltit/stits..
do i have the right channels being logged?
there are many 'idle' threads in here and on google, and nearly everyone is different.

if i remember correctly it is as simple as taking the ltit and adding to idle adapt (stit) and subtracting or dding to braf?

this is what i don't remember, how to adjust the idle trims.

thanks for the comments

here is an example of what i have found.
and no replies on the question asked.

https://forum.hptuners.com/showthrea...-understanding




.

https://forum.silveradoss.com/topic/...sing-hptuners/

IDK if youve tried or read this yet. About a quarter way down the page it goes through STIT and LTIT and idle tuning.

Re: Setting base running airflow via LTIT and STIT

it is as simple as looking at the STIT and LTIT MPIDs. There really is no other way.

STIT is the current adaptive idle "correction" the PCM is having to apply to your base setting to achieve the target idle RPM.

LTIT is the long term adaption to move the STIT towards zero.

It is exactly like fuel trims. LTFT moves to make the STFT zero.


So, if you take the LTIT (gear or PN) and add the STIT this is the total amount that the PCM is "correcting" your base running airflow number by (assuming you don;t have the AC on and fans running etc. which add to the base airflow).

eg.

Base Running Airflow PN (in the editor) = 7.0 g/sec
LTIT PN = 0.3 g/sec
STIT = 0.5 g/sec

This means your base running airflow is too low by 0.8 g/sec for the current operating conditions. Again remember to take account of fans being on etc. (which are all MPIDs as well)

Now the problems begin when the LTIT reaches it's upper or lower limit (as per the editor). This means that the LTIT cannot "learn" any further and the STIT has to do all the work, the kicker is that everytime you go off idle, the STIT is set to 0 and when you return to idle the PCM starts with the LTIT as the "learned position". If it has hit the limit then the STIT needs to do some very fast learning, gernally resulting in RPM hanging high or lowRPM when returning to idle, depedning on which limit it hit.

You have two choices, set the limits wider or set the base running airflow such that the LTITs are within limits.

VERY IMPORTANT. Whenever the STIT is not 0 (or close to) the LTITs will learn, they move VERY slowly so be patient and give them time to adjust after any changes to idle airflow tables.

it is also a good thing to do a cold start log of these numbers so you can see the LTIT vary with temp, ideally it should not move at all if the base running airflow numbers are correct for the idle RPM you are commanding at the given coolant temp.

Chris....

Attachment 157648

Setup a BRAf histogram and plot your MAF rate. Copy and paste that into your table and add 1 g/sec. That's a solid starting point. You always want your idle trims slightly negative.

Setup the histogram and start your data log from a cold start and just let it sit and idle until it's fully at operating temp. You can do both park and drive or just do park and add a couple g/sec in your drive row then data log and see what your idle trims are doing.

thanks for the replies...

i was able to go through my old notes and a few suggestions above and got this taken care of.

sometimes just need a good reminder and there is so much information out there you got to weed through it all to find what you
are lookin for

Quote:

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Originally Posted by Alvin

oh. tune STIT and LTIT to be slightly positive.. .5-1 g/s

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Quote:

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Originally Posted by edcmat-l1

You always want your idle trims slightly negative.

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:confused:

I misspoke. to be clear logging.. you want to see -0.5g/s in the scanner so the BRAF is positive 0.5 is how I was liking thinking in my head as I wrote it.

Have you sorted out the stalling issues? I am having the same problem

Quote:

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Originally Posted by 68camaroLS6

Have you sorted out the stalling issues?

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yes, but i doubt youre having the same issues as i did.

make a new thread and post your tune with a datalog.
Then we can see what your issue might be.

Mine was BRAF, i just forgot what to do, and needed a reminder.