About to throw in the towel nailing down idle

[BBA]

Also, with timing at 30 degrees (if peak torque is at 37 degrees) it will not give you enough room for adaptive idle spark corrections. 7 degrees is not enough to keep the idle from stalling, I would try as little as 10-12 degrees from peak torque. So for your 37 degrees scenario, I would put my base idle timing at 25 degrees. Everything else looks good.

You would be surprised, I can still increase idle by adding timing and I can still decrease idle by removing it via the scanner controls.

Your still missing the point, the high/low octane tables do not totally set timing to their table values at idle, they only reduce timing when airflow goes up. This is evidenced by the stable timing at 12-17º although the tables are set to +30 degrees. This is the one reason my method actually works to smooth out idle and hot start problems.

[12secSS]

Your still missing the point, the high/low octane tables do not totally set timing to their table values at idle, they only reduce timing when airflow goes up. This is evidenced by the stable timing at 12-17º although the tables are set to +30 degrees. This is the one reason my method actually works to smooth out idle and hot start problems.

The idle is not controlled by the Main spark tables (High/Low Octane), it is controlled by the Idle Base Spark table. You are modifying the wrong table. It is evident that you have no clue as to what is table to modify to set your timing to 12-17 degrees. Even after I have explained what tables are. The high/low octane tables are only used when you start moving passed a certain MPH and TPS value (not accessible via HPTuners, but older LS1 have it if you want to look at it).

I will show you how you are wrong.

[5_Liter_Eater]

I have to agree with George, BBA. If your timing is in the 30's but you're only seeing 12-17 then either adaptive timing is pulling a crapload of spark or you're not even referencing the base table at all, your referencing the idle spark table. In the tune you posted above the base table is in the 30's but the idle spark table is not. So I think it's the latter. Thats why I'd match the idle spark with the base spark.

[BBA]

I want the idle base table to be the only one that matters, when the two are matched, the air flow takes over and kills timing at idle.

Trust me, it works. If you have a hard time with idle and hot start with a big cam, all I am saying is try these settings, it does work.


Now if I can just recover the PCM after a flash hiccup doing a write calibration only killed it. The flash looked like it took just fine, no errors on the programming but right after it was completed, the damn scanner won't even see the PCM. Attempted reflash fails on establishing communication. I swear I will never do a write calibration again...ever!!!

[12secSS]

I want the idle base table to be the only one that matters, when the two are matched, the air flow takes over and kills timing at idle.

Trust me, it works. If you have a hard time with idle and hot start with a big cam, all I am saying is try these settings, it does work.

You are proving that your theory doesn't work, your car is idling with 12-17 degrees of timing based on the idle spark table. It has nothing to do with the Main Spark Table. How many times do we all have to say this before you understand it? Do we need Chris@HPT (the MAN that looks inside the PCMs) to open your eyes?

[5_Liter_Eater]

OK, I tried some of my tuning theories and it didn't work out quite how I expected.

First I tried to see where peak delivered torque was. I saw no noticable change to delivered torque when reducing timing from 35 to 25 degrees so I kind of gave up on this right away.

Then I tried zeroing the RAF and disabling adaptive spark, logging the RAF against the min RAF table and commanding 650, 800, 1200...2500 RPMs. I took these numbers and plugged them into the RAF. I also took the differenct in flow between 2000 and 1000 and broke it up into 32 RPM chunks and I got .3 g/s per 32 RPMs. I was going to plug this into the proportional table but it seemed way too high so I cut it in half. So for every 32 RPMs in the proportional table I added .15 g/s. I flashed and the next time I logged and disable the adaptive spark, the RPM's just started climbing, so apparently the RAF #'s I had were too high or the proportional numbers were too high. I decided I was changing too many things at once and I didn't like how things were going so I stuck with the RAF #'s I had and put the proportional and integral tables back to stock. I then set up a histo to log adaptive spark against the RAF table. I commanded each RPM in the RAF table and the histo showed it was taking a lot of spark out. I took the numbers in this histo, which were the average number of degrees needing to be subtracted from each RPM range on the min RAF table, and pasted (multiplied by %) into the RAF table. I realize I'm taking timing degrees and pseudo-converting it to a percentage of airflow which isn't too scientific, but hey, this is experimenting. I copied these into each gear, flashed and logged again. Adaptive spark was having to work a lot less now. I did this another time and got average adaptive spark #'s down to ~1 degree. So I went for a drive and the only "negative" thing I notice is that it takes longer to come down in RPM when the clutch is in of coasting in neutral than I'm used to, not exceedingly long, not long enough to define it as hanging. When it does come down it settles right at 850 (my target idle speed) with no dips at all. Idle quality (meaning the RPM error from target idle when just sitting) has never been a problem for me, just getting back to it. (I guess I should have made that more clear from the get go).

I still want to do some more tweaking o the process but I think it's a decent approach to LS2 idle tuning. I honestly feel like the #'s in the prop and int table are too advanced for most people to be messing with (this coming from an ME grad). I've been talking with another ChemE friend of mine about how to go about changing that table and we can't come up with anyhting that could be done in a decent amount of time and I don't think they are the main problem. I think the key lies in getting the RAF table spot on and then let the prop/int and adaptive timing tables do their thing.

It is still very much a work in progress but I'd like to hear comments. Mine is idling pretty well now and my adaptive spark tables and prop and int tables are stock. I have my base timing copied to my idle timing table and I am idling at ~35 degrees.

[BBA]

You are proving that your theory doesn't work, your car is idling with 12-17 degrees of timing based on the idle spark table. It has nothing to do with the Main Spark Table. How many times do we all have to say this before you understand it? Do we need Chris@HPT (the MAN that looks inside the PCMs) to open your eyes?

I tried the idle table matching high/low octane, it did not work. The only thing that did was setting High/Lo tables in the 30's at 1K RPM and below, then the idle table values were holding.

I proved by what works, if you still want to argue it, beats the hell out of me as to why, my problem is fixed,5 Liters is not. Enough said.

[5_Liter_Eater]

I drove around with the tune above quite a bit last night. The valet at my CTO's holiday party managed to stall it twice but I'm chalking that up to driver error because for me it idles like butter. No dipping, no hanging, RPM error is tight. I'm pretty happy. If someone else wants to try this I'd be curious to see how they come out. As you can see from the tune my idle timing is still quite high (35*) but I don't see any problem with the adaptive timing not being able to do it's job. I may lower it though because like I mentioned I did not see any measurable difference in delivered torque from 35* to 25*.

The only other thing I need to test is whether the commanded RPM can be below ~850. This thread: http://www.hptuners.com/forum/showthread.php?t=15436 points to something I've noticed where I can't seem to get my idle below ~850 unless I use VCM Controls, not even if I zero the RAF table. So if you set the idle too low then adaptive spark will be constantly pulling spark to try and get it down as low as you are commanding.

So the procedure would go like this:

- Set target idle RPM to no less than 850 (for the time being)
- Zero the min RAF table
- Set adaptive spark tables and idle adaptive proportional and integral tables to stock
- Log airflow against the min RAF table, commanding the different RPM's in the table from 650, 800, 1000, 1200. You can only command up to 1200 RPM's in the VCM Controls. For 1600...3000 you need to hold the throttle to keep it at the desired RPMs.
- Paste these numbers directly into the min RAF table for all gears (for auto guys you may need to do this twice, once in park and once in gear w/ the e-brake on)
- Now log adaptive advance against the min RAF table. Command the RPM's again, just like before. Copy and paste these numbers (paste special, multiply by %) into the appropriate cells. (again, auto guys will need to do this twice) Rinse, repeat until the adaptive spark numbers are +-1 degree.

I'd really like it if someone were to try this. I've attached the config I used. histos 10 and 11 will do the job. Most of the other histos will be of no good to anyone as they utilize my user defined PIDs for my AEM through my AC pressure sensor.

[LazMan]

After reading all this, now I have a headache. Glad its gotten better for you 5L.

As for the timing "discrepancies" between BBA and 12s, the 2005 E40 is a "special" computer. Not special in the "what a lovely thing" way, but in the "mildly retarded" way.

Don't misunderstand, I love mine, but it just seems like it was a 1 year (except the GTO and a few other cars) transitional piece for GM.

[5_Liter_Eater]

I'll admit it's a transitional PCM. Thats what we get for buying a first year model. I am not sure I see BBA's point though. He keeps saying that by increasing the base spark table into the 30's this makes his idle better even though his idle is only 12-17*. 2.2 has given us quite a few more PIDs to play with. My config logs overall advance, idle base advance and adaptive advance. My tune is different in that my idle and base spark tables are identical but I think if BBA were to log using my config we would see that the base spark table is not coming into play. The idle spark table is defining the advance and the adaptive advance is adjusting that number. I don't see what increasing the base timing table is doing unless it is coming into play while moving.

[BBA]

I'm glad your idling better, your timing tables are changed in the same fashion this TBSS tune is, but I kept taking it a little farther in the low RPM high flow ranges simply because it made a positive difference in idle. It made a difference and I ended up with the same number all the way down the tables to high AF regions.

My whole reasoning was not to get the base timing up necessarily, it's to prevent the hi/lo octane tables from dropiing timing on airflow fluctuations, which it was doing (badly) while I was watching the scanner. That's how I figured the problem out, by eliminating the MAF sensor effect of destabilizing timing in the high/lo tables, I was able to get a consistant smooth idle and cure the hot start problem.


I know what the 'experienced' people say, and I tried all the suggestions, but the reality was the base idle table by itself did nothing to cure the problem. Again, what the end result of my method achieved was not in setting timing via the high/lo tables, but instead preventing the bad effect of cam surge airflow from destabilizing timing at idle. The high low tables do effect idle timing in a bigger way than the base idle timing tables, may not be designed that way, but that's what it does. I guess you could equate that to using ported vacuum on a distributor, keeping surge from effecting timing and therefore allowing a better idle quality.

[Kelp]

Removing the effect of airflow on timing at idle RPM ranges really did stop all the problems.....

Like I said before, big cams confuse the MAF sensor and the MAF sensor kills timing, so at idle, you just don't need the MAF freaking out and reducing timing on normal cam surge airflow fluctuations.

BBA,
My big cam gives transient timing drops and the engine bangs around at low RPM cruise. I matched the idle and main spark in that area and it helped about half-way. - but how can I D/C the MAF sensor just at those low RPMs only ?

[LazMan]

I was looking at your Idle Overspeed tables vs your idle UNDERspeed tables. You cut the timing mod at anything over 200rpm. Shouldn't you be consistent and do the same on the overspeed tables?

I've had the following problem: My PCM pulls too much timing on deceleration because the engine is being spun by the tranny (automatic). I just realized this is where that is happening!

Anyways, this is what I'd try on your Idle Overspeed Spark vs RPM Error. (I'm doing it to mine during lunch.) (See attached.)

-Laz
PS: I'd still like to see you use something closer to BBA's 17* Base Idle Spark table, not your 35* one.

[5_Liter_Eater]

You're right, that doesn't make much sense but thats how it is stock. I returned all the adaptive idle and proportional and integral tables back to stock. In my logs I don't see adaptive spark going anywhere near that high so it's not a factor, but it doesn't make sense. I'm pretty surprised how well its idling with everything stock and the RAF tuned in.

Have you logged that it is the adaptive spark that is pulling the timing? My timing gets reduced on decel as well but I think it's just referencing the coastdown spark table. I don't log a bunch of adaptive spark.

Something I noticed this morning was that adaptive spark is coming into play when cruising as well. I would think it would only be active when pedal position was ~0. Also, my RAF ends at 3000 because I was commanding the different RPM's while in the driveway and I didn't want to go any higher so you'd think that my adaptive spark above 3000 would be outrageous but it's not.

I have noticed a few times where idle has dipped but for the most part it doesn't. I don't know what would be causing the occasional dips though.

I think I am going to reduce the idle range timing back down to ~25.

[LazMan]

I was looking at some old scans and I'm almost convinced that the way my timing goes to near zero (sometimes negative!) is because of the Overspeed adjustment. I had given up on finding what it was, and had never made the connection (I always thought it was DFCO somehow, even when DFCO was disabled.)

The only reason I am not 100% sure as of yet is because I've not proven it by having it NOT happen (which I will when I go for a drive right NOW actually ... so later!)

[LazMan]

I saw it on the scanner live.

Before the change, timing dips and stays there until I stop. After the change, timing dips and then quickly shoots back up. It was very nice, gave the throttle time to adjust itself.

I endorse this change (tentatively). I'm keeping it on mine. I cut all the tables between 160 and 200rpm to zero, over and underspeed, except the park/neutral ones (since i'm automatic). In your case I might cut those too.

[Ossirian]

any critiques on my tune, i think its idling ok, some warm start up issues, its an 06 gto m6 with a 236/238 cam

[5_Liter_Eater]

Found a few things yesterday after playing with my config:

Idle adaptive spark only comes into play at 0 MPH. Anything more and it locks out at what it was right before it left 0 MPH although this value does not seem to affect timing once moving. This doesn't make sense. My idle is fine while coasting so if it doesn't need the idle adaptive spark then why does it need it in P/N? Granted I'm referencing the coastdown table at that point but still... So this means most of the idle adaptive spark data I collected was irrelevant. I edited my config to only log adaptive spark when MPH < 1 and I think that by sitting in the driveway and commanding different RPM's I should get good adaptive spark data that I can use to tune the RAF with but I dont know if this is the best route.

I tried lowering my timing to 28 and I also made a RAF change based on the bad data prior to realizing it locked out > 0 MPH and I got surging. I reversed both changes quickly because I had to be somewhere so I can't say which change brought on the surging, likely the RAF and not the timing. I'll try lowering it by itself sometime soon.

[Phil99vette]

This will probably sound stuipid but use your clutch for changing gears only. If your coming to a stop light either:
Leave the car in gear to slow down
Downshift as normal
Put the car in neutral
Push clutch in to ONLY CHANGE GEARs

I had a car I tuned and couldn't figure out how the clutch position switch changed things but when the clutch is pushed in your followers/transition tables are 0'd out. When you release the clutch they go back to the normal values.

Previous owner complained about surging idle, he drove it for 5 minutes - idle surged coming to lights, I got in and drove it and the idle was perfect. Owner looked and said what did you do? Why doesn't the idle surge anymore? I told him that I don't ride the clutch. Now he doesn't either or have the idle problems.

[5_Liter_Eater]

I'm just pointing out that there are multiple factors at work. The proportional and integral tables as well as the adaptive idle timing. The timing does not come into play when coasting so why would I need it when not moving?