idle logging, anyone figured it out?

[ozorowsky]

Looks like my STIT in p/n is around .12 and in gearis .22 I think I want to be closer to zero. My LTIT stays at .07 anyone have any good info where to go from here?

[checkmate]

Chris posted this a few days ago.

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....

[ozorowsky]

right, so say at 180* my stit is .12, and ltit is .07 So I would ADD .19 to my base running airflow vs ect at 180* right???

[98A4LS1]

Good question OZ, maybe someone can elaborate more on the above post.
The explanation is good, just not how to make the right changes ie actual values with an example.

[WS6snake-eater]

ttt up up up

[ozorowsky]

yeah I'm gonna add this into my "tuning for dummies" write-up once I get the DEFINITE answer.

[SideStep]

yeah I'm gonna add this into my "tuning for dummies" write-up once I get the DEFINITE answer.

I am doing this today at lunch... I will let you know how it goes...

Just installed new cam (F13 Futral), 230/232 .595/587 112lsa +4, and it idles pretty good right out of the box.... very suprised....

[SideStep]

I am doing this today at lunch... I will let you know how it goes...

Just installed new cam (F13 Futral), 230/232 .595/587 112lsa +4, and it idles pretty good right out of the box.... very suprised....

I just logged my idle from start-up to 192* degrees (f). Idle is set to 900rpms after 154* ECT

ECT Average (roughly) Combined STIT and LTIT
90-155 -.09
155ish 0
155-192 .1



??? This seems to be pretty damn close right out of the box??? The car does idle fine though...

Any thoughts...?

My only concern at the moment is the rpms do not fall as fast as I would like. Would this be fixed by adjusting the "Throttle Follower Decay"? It does not hang ... or hunt/roam for idle.....

[Screamn03]

I just started playing with this last night and my LTIT was .07 and STIT was 0 so I just applied +.07 to everything in the base airflow table and then started logging it again and I was seeing a good correction (about -.06 STIT, the LTIT were still +.07) so it seems to work. After driving it around for about a half hour I noticed that it was still a little unsettled but I just left it alone and I'll get a couple days or normal driving on it before I mess with it again.

I wasn't having any idle problems except sometimes the idle would dip when coming to a hard stop with you pushed the clutch in to early. I did notice the car seems to start better this morning, like it lit right off. Could that be from messing with this table?

-Mike-

[WS6snake-eater]

well I tried messing with it a little tonight, and I must say I am very discouraged. my LTIT is at -.40 and my STIT is at -.02 while in gear at idle. So I went ahead and subtracted .4 from 177* an up. Nothing happened...I even let the car sit in gear at idle for 15 minutes, to see if the LTIT would move. It did actually go to -.39 but remained there indefinatley. It seems that no matter what changes I make wether they be postive or negative , have an effect on my LTIT's. Right now my car idles great in park and it even settles into a nice little idle in drive once it has been sitting for 3 or 4 seconds. But it sure sucks donkey balls when it's time to come to a stop. The only way I can keep it from surging is by tapping the brake pedel to build up some vacum.

[Dixit]

For us Noobs that dont know all the terminology, whats LTIT and STIT?

Dixit

[SideStep]

For us Noobs that dont know all the terminology, whats LTIT and STIT?

Dixit

LTIT = Long Term Idle Trim

STIT = Short Term Idle Trim

[WS6snake-eater]

Ok I finally figured out why I was having problems...Hopefully the rest of you have not been dumbassess like me. Mine was actually way off. I was showing -.4 LTIT. I then tried to correct for this by subtracting -.4 from the corresponding ECT in the table. However I was not noticing a very good correction. In fact it was hardly moving my trims at all. So I decided to look into it a little further. After 3 days of this crap it finally hit me in the face. The scanner is reporting in lb/min however the IA vs Cool table is setup in g/sec. You have to convert it over to g/sec. So instead of subtracting -.4 I should have been subtracting -3.03!!!!!!!!!

Hopefully none of you have been making the same mistake, or if you have you can learn from mine.

FWIW, my table was so far off that I had a real hard time getting the car to start after making such a drastic change to the IA vs Coolant table, due to the fact that the car was still using the old trim. I actually had to hold down the throttle a slight bit to get the car to start then let off very very lightly. The idle would then bounce up and down quite a bit, then the car would die. However after 3 or 4 starts, it finally stablized itself. It took a good 20 minutes of idle relearn procedures, but my trims are now resting at or near 0. Good luck guys, and remember:

YOU CAN NOT MAKE A 1:1 CHANGE OF WHAT YOU ARE SEEING IN THE SCANNER. YOU MUST CONVERT YOU VALUES IN THE SCANNER FROM LB/MIN TO G/SEC.

[SideStep]

Ok I finally figured out why I was having problems...Hopefully the rest of you have not been dumbassess like me. Mine was actually way off. I was showing -.4 LTIT. I then tried to correct for this by subtracting -.4 from the corresponding ECT in the table. However I was not noticing a very good correction. In fact it was hardly moving my trims at all. So I decided to look into it a little further. After 3 days of this crap it finally hit me in the face. The scanner is reporting in lb/min however the IA vs Cool table is setup in g/sec. You have to convert it over to g/sec. So instead of subtracting -.4 I should have been subtracting -3.03!!!!!!!!!

Hopefully none of you have been making the same mistake, or if you have you can learn from mine.

FWIW, my table was so far off that I had a real hard time getting the car to start after making such a drastic change to the IA vs Coolant table, due to the fact that the car was still using the old trim. I actually had to hold down the throttle a slight bit to get the car to start then let off very very lightly. The idle would then bounce up and down quite a bit, then the car would die. However after 3 or 4 starts, it finally stablized itself. It took a good 20 minutes of idle relearn procedures, but my trims are now resting at or near 0. Good luck guys, and remember:

YOU CAN NOT MAKE A 1:1 CHANGE OF WHAT YOU ARE SEEING IN THE SCANNER. YOU MUST CONVERT YOU VALUES IN THE SCANNER FROM LB/MIN TO G/SEC.

Damit!!! I did the same thing.... I am using your advice now....
: I feel like a noob.....

Thanks

[WS6snake-eater]

Sure hope it works out for you.

[Screamn03]

YOU CAN NOT MAKE A 1:1 CHANGE OF WHAT YOU ARE SEEING IN THE SCANNER. YOU MUST CONVERT YOU VALUES IN THE SCANNER FROM LB/MIN TO G/SEC.

LOL, time to go make some corrections to mine. I was starting to wonder why they didn't seem to change much. Good find ...

-Mike-

[sspeedracer]

FWIW, my table was so far off that I had a real hard time getting the car to start after making such a drastic change to the IA vs Coolant table, due to the fact that the car was still using the old trim. I actually had to hold down the throttle a slight bit to get the car to start then let off very very lightly. The idle would then bounce up and down quite a bit, then the car would die. However after 3 or 4 starts, it finally stablized itself. It took a good 20 minutes of idle relearn procedures, but my trims are now resting at or near 0.

Thanks for the above info. The LTIT on my car was pegged at -3.0 with STIT ~ -.4 so I changed base running airflow in two steps. In other words I added 1/2 of LTIT+STIT to the base airflow. Worked well.

I also just finished logging LTIT/STIT data while turning on and off the low/high fans via Scanner and the AC manually. As soon as I crunch the numbers I'll have a better airflow numbers for those accessories.

Is the MAF being used to target the base running airflow? Just wondering 'cause I get offsets when logging various flow rates along side of the LTIT/STIT and base flow data. I havent calibrated the MAF yet, after MAF calibration, will I need to retune base airflow?

[SideStep]

Sure hope it works out for you.

I just tried it and yes it did.....

.. have to laugh at myself :

[WS6snake-eater]

Well I just about got it nailed down...I'm going to use the above suggestion, and disable the fans when I start it up this afternoon to get some better numbers for in gear. I've got park dead nuts on. After I nail down the in gear with no fans, I will re-enable them one at a time and see how much they offset. From there I can enter those values into the fan offset tables. This is some pretty good stuff!

[sspeedracer]

How does the VCM look at the idle base running airflow temperature? ie, does the 20C column get used for all ECT between 10C-30C or from 20C-40C? Does it interpolate?