Can't figure this out- underspeed idle spark

I'm sure I'm just missing something but I don't see it.
It does not matter where I set the idle spark advance, the underspeed spark table will not add any timing to catch an underspeed condition.
Say I set all the spark tables at 24* for the idle area. When the engine dips below the commanded idle speed, the underspeed table does not throw in any timing at all. The log shows a max timing of 24*. If I set it at 20*, it's the same thing. 20* is the max timing shown in the log.
On startup it surges and does the same thing. The timing flatlines at 24*.
The overspeed table is operating.
I have 5* in the idle spark adder table but that was just an experiment to see if it did anything.
Now I don't know if my overspeed and underspeed tables are optimized but with one not working at all, it's pretty hard to work on that.
I've added proportional idle air but I need to get the spark tables fixed before I mess any more with that, I suppose.
Idle air final minimum is high enough, I think, but maybe some input on that would help me.
This thing has never idled "just right" and I really want to nail it down.
Can someone look at this and see what I'm doing wrong?
With a cam this small, I would think I should be able to get it to idle with no wierd surging at startup.
Actually, once it's been running for a few minutes, It's fine. It never stalls or anything. It's just not "right" If that makes sense.
It is a 2011 CTSV with a 224-232-116 cam and 60# injectors.
My fuel trims are + - about 2% in the idle area so I think I have the fueling at least close enough to idle decently.
Is there something else in the idle area that I'm just plain overlooking?
Right now it's a MAF only tune because I just haven't figured out the Virtual VE stuff at all. But that's for another day.
I've attached a log of it starting up so you can see where the timing stalls as it surges.
Also attached is the tune file.
I've searched till I'm blue in the face and don't see anything to help me.
Any help would be greatly appreciated.

I had a similar problem, your high octane table is set to 24 degrees in the idle area, it wont exceed that value (or at least the scanner wont show it exceeding that value), if your base idle timing is 24 also the underspeed cant add anything.

Thanks. I tried that but now am more confused than ever.
When does it reference the idle spark table? If I put the stock numbers in the regular high octane table, it idles way up in the 30s and doesn't seem to reference the idle spark table at all.
I know I've seen several posts, from guys who know a lot more than me, that say to make both the regular spark table and the idle spark table the same. (in the upper left corner)
I do not understand what table is being used on startup and at idle. Can anyone clarify?
That being said, after changing the main spark table, it still idles like crap after startup, even though the timing is now completely different. It really acts pretty much the same.
I see a lot of posts here about idle timing being the key. It doesn't seem to make much difference no matter what the timing is set at.
Once you get it to settle by holding the throttle for a few seconds it is about 85% good. A little rough but not a lot of surging.
On startup it revs up and dies if you don't hold the throttle.
I think I have plenty, if not too much, idle air. Startup airflow has been raised a bunch to get it to start without touching the throttle.
Proportional is up about 50%. I'm afraid to go up any more on any of these tables as it seems like nobody else has to go that high.
Can anyone clue me in? Thanks

Why do you need 24* of timing during idle?

What is the stock timing table set at?

How did you come up with 24*?

If you have too much idle spark thing become erratic.
Sometimes you don't need to add timing at idle.

Just get the idle airflow tables perfect.

I was just trying different things.
With 24* in the idle table it idles mostly up in the 30s.
With 16* in the idle table it idles in the mid to upper 20s.
It moves around but seems to stay above whatever is in the idle table most of the time.
I thought the timing should osscilate around whatever number is in the idle timing table with the over - under tables compensating. It doesn't seem to do that and I don't understand why. What is making the timing hang much higher than commanded?

Try this:

1) The Hi and Lo octane tables set to 24 degrees. This effectively put a ceiling on the total timing. So the various spark adder tables have no room to work. Reset both tables back to stock then add 4 degrees. If you see any knock, reduce timing in those cells only.

2) Your idle spark adder tables are set to +5 degrees at all temps. You said this was an experiment, so reset these back to stock.

3) The idle spark advance and coast down table are set to 24 degrees. Reset back to stock then add 3-4 degrees. For a decent idle, a low or soft timing is very desirable. If you set timing close to maximum torque value, you can get a very unstable idle as it becomes hyper sensitive to any air/fuel/timing changes. A low spark advance makes it much less sensitive to changes thus give the adder tables more leverage to control idle speed.

4) The IAT spark retard table adds ignition advance at temps below 95 degrees and starts pulling timing at 131 degrees. Is this stock? If not, reset back to stock and let this table do its job. Higher IAT results in a faster burning mixture, so you need LESS advance for the optimum spark advance.

5) I would wager the reason the timing is going into the 30's is the various air flow tables need work. It is adding ignition advance to compensate for bad air flow tables to achieve the targeted idle RPM.

That is way too much idle timing for that thing. When I get back from out of town, I'll take a look at your file.

Step 1, put it back to stock.

Step 2, change nothing but inj data, idle speed and add about 10% to the idle airflow table.

Step 3, turn off your long term fuel trims.

Step 4, slowly, and gently dial in the idle area of your MAF table using short term fuel trims. Just give it a little bit of throttle to keep it running, and to hit several cells in the table. Only reason you're doing this is to get it close. Run the histogram, and copy and paste to your MAF table.

Step 5, slowly add air to the base idle airflow table until it idles. If it has trouble starting, but will idle if you give it help starting, add some to the startup airflow. I usually do this only at the temps needed, to avoid start up flare at temps where it doesn't need any additional air.

Leave all the timing tables alone for now. The factory settings should work fine for a cam that small. The procedures above should be about all you need to get it to start up and idle and drive around.

I got this far yesterday. It's a lot better. It started with just a little flare and settled pretty quickly. It still has a little instability at idle, but not bad.
Cold start this morning started right up with no throttle, was smooth for 3 or 4 seconds and then had some large surges that went up to over 1500 and down to 400. They slowly settled to being pretty smooth after 30 seconds or so.
Once that's over with it drives fine.

I had no idea that the main spark tables had any effect on idle tuning. I've read that they should be the same as the idle table. Changing that and taking timing out of the idle table helped a lot.
I was playing in the 20* to 24* range because my Tuning School book says 23* is a good average. ( I have about $2K in books and DVDs and I'm still as confused as ever at idle tuning):doh:
I also have the proportional table changed as per the Tuning School, so I guess I'll put that back to stock as well.
I have my Grandkids this morning so I'll try what was suggested later today and put a lot of stuff back to stock and start over.
Thanks. Just what I learned yesyerday has made quite a difference.
I've attached the last tune from yesterday as that is what I'm working from now.

Yea, I would totally ignore what that book says. I've yet to come across a Gen IV setup that wants tons of timing to idle. My buddy's 441 with 14.8:1 pistons idled best with 19*.

in your book
when they say 24 is a good number
they are assuming that your timing around 19 to 21 ,, then u get it up to 24 if you need

its a book ,, and all cars are different ,,
if you Paid money for your book
then you can call the tuning school support and they can help u

Quote:

---

Originally Posted by edcmat-l1

Step 1, put it back to stock.

Step 2, change nothing but inj data, idle speed and add about 10% to the idle airflow table.

Step 3, turn off your long term fuel trims.

Step 4, slowly, and gently dial in the idle area of your MAF table using short term fuel trims. Just give it a little bit of throttle to keep it running, and to hit several cells in the table. Only reason you're doing this is to get it close. Run the histogram, and copy and paste to your MAF table.

Step 5, slowly add air to the base idle airflow table until it idles. If it has trouble starting, but will idle if you give it help starting, add some to the startup airflow. I usually do this only at the temps needed, to avoid start up flare at temps where it doesn't need any additional air.

Leave all the timing tables alone for now. The factory settings should work fine for a cam that small. The procedures above should be about all you need to get it to start up and idle and drive around.

---

I did EXACTLY what you recommended.
The STFTs were a pretty close (+ - 2%)
I started with your recommended 10% idle airflow and started adding 5% at a time and testing it each time. Even with the 10% it would idle nicely if you didn't touch the throttle after it settled. It would not idle at all after startup unles you held the throttle and SLOWLY let it come down to idle speed. As soon as you touched the throttle again it would drop through the commanded idle speed and surge up and down until it either stalled or I caught it with the throttle.
I added another 5%, and another and another. Then another 10%. It still did the same thing.
Then I added 25% just to see if it changed anything and it just about quit doing it. It was getting a very slight "cruise control" condition. I'm not surprised with airflow numbers that high.
I backed out 15% and it started the surging again. I added 50% to the proportional table and it is "pretty good". I'd say it's 90%.
I see posts on here that say it's not necessary or even recommended to mess with proportional air but it seems that is the only way to fix this thing without jacking the idle air even more.
I was not adding airflow accross the whole table. I was just adding it in the lower RPM range. I'm not sure if that was the right way or not? I'll blend it into the higher RPM are if you think that's what I should do.
The problem I see is that there is no way that I should NEED to have such high running airflow numbers. I see tunes from professional tuners running big cams in big motors that run lower idle airflow numbers than this.
Could you, or anyone who is a whole lot more experienced than I, possibly look at this and explain to me what else may be affecting the idle and forcing me to add so much idle air? Should I be playing with timing more? It seems like the over - under is working OK now, I think.
Does this seem abnormal?

Besides all the books and DVDs, I've paid for two professional tunes (although this is a completely different combination as it was then) and it's never idled properly.
One was a W4Me mail order tune and it was just horrible.
I had the last engine combination running better than either of the pro tunes but it was still out of whack.
While it does run pretty good, I think the numbers are out of line from what would be deemed normal.
Thanks for taking the time to look.

I've seen higher airflow numbers. Those aren't crazy high by any means.

I would ramp the airflow up at less than idle speed. Also, highlight the 800 rmp to 3500 rpm and interpolate between horizontal bounds.

Quote:

---

Originally Posted by edcmat-l1

I've seen higher airflow numbers. Those aren't crazy high by any means.

I would ramp the airflow up at less than idle speed. Also, highlight the 800 rmp to 3500 rpm and interpolate between horizontal bounds.

---

I added 5% at 200 and 400 then interpolated as you suggested.
I'll try that.
Here's an update since yesterday. It ran real well driving around. I did a couple of hot restarts and let it cool for an hour or so. That was fine also.
But this morning, at cold start, it surged very quickly over 1500 and back down until almost stalling about 6 times. It seems to start just fine and then start the surging after about 5 seconds.
Then it settled and was fine. I'm not sure whether it settled on it's own or I caught it with the throttle, though. I can't temember.
Is there anything I can adjust for this surging just after startup?
What happens right after startup that changes after 5 seconds. It's definately not in closed loop yet. Maybe there's some sort of after start enrichment that is decaying away?
Thanks

Email or post a data log.

Set engine>idle>rpm>adaptive idle>proportional & integral>enable RPM error to 75 rpm for both.
Chase idle speed with timing, not the throttle blade.

OK. Here's a log of the cold start and the file that's in the car now.
It started right up, waited a couple of seconds and then started the surging. It settled on it's own after a few swings and then idled fine.
I can see that TPS is pretty steady but there are big swings in timing.I just don't know which table is effecting it.
Thanks

Quote:

---

Originally Posted by wstaab

Set engine>idle>rpm>adaptive idle>proportional & integral>enable RPM error to 75 rpm for both.
Chase idle speed with timing, not the throttle blade.

---

I experimented with these setting and what worked best for my combination was 15 and 12 rpm but I have a mild cam.

In principle I would agree with you but if the RPM has a tendency to jump around a lot, it may be bad airflow tables. Get the airflow tables tuned first. The RPM will have a certain natural + - depending on the cam. Timing is used as a quickest way to control it but if the airflow tables are too far off, timing can't do it all.