2010 CTS-V Idle Tuning

[Da-Grump]

Greetings,

Long time lurker - second time poster here. I need some guidance on smoothing out the idle on my 2010 CTS-V, please.

It has upper/lower pulleys, modest cam with -9 degrees overlap, LS7 TB, CAI, post-boost meth/H2O injection, ZL1 lid, and tuning by me, a rookie tuner.

The idle is a little rough - it feels somewhat like a lean miss, but not a lope. If you look at the pic below, the left half is idling in gear and right half is in park. This is a screen capture from the attached log file. It's a 3-minute file where the car was warm started, driven around the block, and then parked in the garage to idle. There were four misses captured during this time. Idling starts in gear at the 2:26 point and continues in park at the 2:43 point.

Also, the O2 plots from the NB sensors are strange when idling or coasting. As soon as gas is applied, they smooth out.

The attached tune is currently set up as MAF only and is minimal until I get this figured out. Any help in fixing these issues is greatly appreciated.


2010 CTS-V Idle.jpg

[JBZ]

you might try and check out these 2 threads and see if either of them are helpful.

http://www.hptuners.com/forum/showth...e-tuning-guide
http://www.hptuners.com/forum/showth...-perfect-idle!

[Da-Grump]

Thanks or the suggestions, but I've already been through both those threads. I tried some of their procedures, but nothing changed. If I could figure out what's causing the erratic O2 spiking at idle I think I may be able to fix it. The WB indicates it's not an afr issue, but I'm not so sure anymore.

[JBZ]

do you have aftermarket exhaust? it could be your closed loop fueling or O2 settings. if it swings too often it can make the engine surge. I have pretty indepth thread I started about NB O2 settings with headers. mmaybe there are some answers in there. http://www.hptuners.com/forum/showth...g-with-Headers

hope this helps but maybe not, I don't have a cam for what its worth.


OK, I just looked at your log again and I would bet that's what the problem is. I bet whats happening is that because of your cam it has put you in a different airflow mode in your closed loop settings and is swinging to often at idle. you might try either changing your airflow mode to the left (decreasing it some) or increasing your integrator delay table. i would bet you have moved up to the airflow table 8 at idle and its just swinging far to often. if you look into that thread it may help give a better explanation.

[Da-Grump]

do you have aftermarket exhaust?

Stock exhaust manifolds, hi-flow cats, replaced crimped sections, and stock mufflers.

Thanks for the airflow mode suggestion. I'll check out that thread.

[Da-Grump]

I read through that thread and there are some new concepts that I still need to wrap my head around, so more reading is needed.

I started with your basic changes first:

Proportional Airflow x 0.8
Integrator x 1.4
Airflow Mode table to match DOD values

Then I did a cold start, drove around the block, and let it idle for about a minute. It still idles a little rough and there were still misfires, but the NB O2 plots look much better (see pic below). It looks like we're headed in the right direction. What to change next?

2010 CTS-V Idle Rev1.jpg

[JBZ]

So its probably best to determine where your idle falls in the airflow mode table. Then try and take your idle integral number...like 1200 something and put that in the cell that your seeing your actual idle airflow. Im guessings its now in the 8 cell. Just try that to see what it does for you, easy enough to go back to what you had.

So i noticed in your screenshot the idle spark advance goes up and down with rich lean swings. So if you can extend the timeframe between swings (i.e. Integrator delay) that may reduce the surging. I will look at the log later tonight on my pc, on the pad now.

[Da-Grump]

So i noticed in your screenshot the idle spark advance goes up and down with rich lean swings.

Yes, I saw that in previous logs. That's what made me postulate there was an afr issue, in spite of what the WB was indicating. I'll await your further review. Thanks again.

[JBZ]

Yes, I saw that in previous logs. That's what made me postulate there was an afr issue, in spite of what the WB was indicating. I'll await your further review. Thanks again.

Go ahead and give it a shot and see what it does for you...again worst case scenario is nothing so you can put it right back

[GHuggins]

JBZ, could you go over a step by step on the best way to adjust the airflow modes I'm always interested in learning and you seem to have made some pretty good leaps on this...

[Da-Grump]

Go ahead and give it a shot and see what it does for you...again worst case scenario is nothing so you can put it right back

Sorry, give what a shot? Are you saying increase the values in the Integrator Delay Airflow table?

[JBZ]

Sorry, give what a shot? Are you saying increase the values in the Integrator Delay Airflow table?

so its looks to me like you landing in cell 8 at idle based off of your MAF (LB/HR at the end of the log) so what I'm suggesting is putting the entire integrator delay table back to factory values...for now. then take cell 0 (value = 1127.625) and copy that into cell 8. just see if that helps...no guarantees.

if I take a look at your log file and compare it to mine at the same zoom your is switching a lot faster and most likely is contributing to your problem. there are a few other thing that you may try to stabilize your idle, you could raise your idle RPM a little bit and raise your idle timing by a degree or two as well to see if that helps.

[Da-Grump]

Thanks for the concise instructions - I'll give that a try and report back.

I've played with idle RPM, base running airflow, timing, and the various adaptive idle parameters trying to resolve this. Nothing seemed to have an impact. Perhaps after your suggested tweak, they'll be more effective.

[Da-Grump]

so its looks to me like you landing in cell 8 at idle based off of your MAF (LB/HR at the end of the log) so what I'm suggesting is putting the entire integrator delay table back to factory values...for now. then take cell 0 (value = 1127.625) and copy that into cell 8. just see if that helps...no guarantees.

Just did this - no discernible difference. The idle RPM swings actually felt a little worse. Next suggestion?

[Da-Grump]

One other quick thought - my Base Running Airflow is currently set at 1 g/sec over stock, and the idle timing is +2 degrees. Is that enough airflow to not influence these tests? My cam has 24 degrees more duration than stock, with -9 degrees overlap.

[JBZ]

its still swinging way to fast, from the only spot I see logged at idle at the end of your log anyways. the integrator delay didnt change the swinging like it should. here is a screenshot of your log at idle and one of mine from yesterday. a couple of things to take note of, your maf trace (dark blue) your idle advance (white) and adaptive advance (green) all jump with the rich/lean swings. mine do to but not as dramatic as yours does. most likely it is the cam. you may be too low of an idle RPM, you may need to mess with your integrator delay, your timing and min idle airflow may not be ideal or the RPM error P&I gains may not be ideal, it could be many things...sorry but that's all I got.

you really need to get that KR taken care of, I would be wayyyyy more concerned about 5.2 degrees of knock retard your seeing than the unstable idle. you are seeing KR all over the place.

[Da-Grump]

you really need to get that KR taken care of, I would be wayyyyy more concerned about 5.2 degrees of knock retard your seeing than the unstable idle. you are seeing KR all over the place.

Crap! I uploaded the wrong file. That was a quick WOT test to check my baseline fueling. I had the meth/H2O injectors temporarily disabled.
Here's the right file.

[Da-Grump]

Now I've taken your three table edits and added more idle airflow and 50 RPM, and put idle timing back to stock. This resulted is a noticeably smoother idle, but the O2 sensor data still looks strange. Also, there is some KR at idle. See pic. I noticed this on prior logs, too. Is this indicating that I'm still too lean?

2010 CTS-V Idle Rev3.jpg

[GHuggins]

O2 data looks like you might almost be misfiring?

[Da-Grump]

O2 data looks like you might almost be misfiring?

Sometimes, but not always. When it does misfire, there will be 4-6 during a 5-minute log.