Idle adaptive advance question - almost have a perfect idle!

[Random84]

I am really close to an otherwise PERFECT idle on my setup. I've lowered the timing on the idle spark and high output spark tables after reading many threads that come up with my searches... and it has helped.

Basically, all that's left is that when I push the clutch in, the idle adaptive advance is -11 or -12 by default (ie the throttle body idle air controller?) - then it works up to zero over a few seconds while at idle and... whalla - I have a perfect idle at 725 rpm or so with my stage 2 cam - that the tuner said would not be possible. I have no other issues, surging or other problems, so I believe idle spark is pretty much where it needs to be at around 15-17* advance.

So can anyone tell me what table(s) contribute to the idle adaptive advance parameter? My searches consistently come up with idle threads that deal mostly with starting from scratch and don't seem to address that specifically?

Screen shot of the phenomenon: note the idle adapt advance (light blue line) starts at -11.5 and creeps back to zero, then will stay there at idle with no lope. So how can I make it START at zero?



sequential screen shot of the same scan:


Here's my current tune file:
Stage 2.57 - 1deg less timing at 4800 RPM, leaned out idle with less idle spark in HOTable.hptStage 2.57 - 1deg less timing at 4800 RPM, leaned out idle with less idle spark in HOTable.hpt

ETA: 2013 CTS V 6.2 LSA, manual trans with an LS7 throttle body, pulley and cam (230's / 240's?), around 650 RWHP. Throttle body cross-sectional area and injector constants were updated and are correct to my knowledge. Again, all other areas of driveability are excellent. Just the slightly higher than commanded idle that goes to perfect over 2-3 seconds when stopped.

[schpenxel]

edit / correction:

Final min airflow. Adaptive idle positive = not enough airflow (increase min air), negative = too much air (reduce min air)

[pacian45]

What mods are you running to get that power, if you dont mind? Boost level?

[mowton]

Without seeing the tune or logs, if Min Idle air doesn't help then look to reduce the Max Idle Area for moving (first value in table, not the brake value) and coast down timing. Do this in coast down as the first log shows you are moving.

Ed M

[Random84]

What mods are you running to get that power, if you dont mind? Boost level?

2013 CTS V Wagon, Manual transmission. Stage 2ish cam, stock heads, ~28% overdrive/pulley on the supercharger, injectors, ported supercharger, headers and the usual cooling mods.

[Random84]

Final min airflow. Adaptive idle positive = too high, negative = too low

I raised the final minimum airflow ~5% and it made no difference. if anything, cold start is more choppy but the idle adapt advance issue is unchanged.

Without seeing the tune or logs, if Min Idle air doesn't help then look to reduce the Max Idle Area for moving (first value in table, not the brake value) and coast down timing. Do this in coast down as the first log shows you are moving.

Ed M

Idle adaptive advance only starts when "idle" is commanded - for me that is at zero mph.

I took a short datalog of warm idle, going into 1st gear and then pressing the clutch to idle, then coming to a complete stop while idling. Clutch in or out made no difference at a full stop.

log file: 111615 ECM2.58 warm idle and start-stop with clutch in for idle adv.hpl
tune file: Stage 2.58 - increased idle minimum airflow_adjusted MAF curve at warm idle.hpt

[schpenxel]

I said that backwards, my bad. I'm going to edit just in case anyone else finds this thread later.

If adaptive idle is positive then the min airflow is too low (i.e. it's increasing timing to help increase output since it's not getting enough air).

If it's negative then it's removing timing / engine output due to too much air.

Sorry about that

edit:

Notice around frame 4740 you're at ~23% TPS, -9* adapt advance and 800 RPM's. The throttle closes down to 20% by frame 5098, adapt goes to basically 0* and RPM comes down to the 725 RPM's being commanded.

Try engine braking sometime and get an idea how low the TPS goes during that.. that should give you an idea what the min airlfow table is commanding. If it's going lower than you usually see at idle, then increase min airflow table.

If it's staying higher than you see at idle (when totally stopped and idle adapt timing close to zero) then min air is too high

It's just what has worked for me.. play around with it. You're already doing better than most "tuners" out there!

[Random84]

I said that backwards, my bad. I'm going to edit just in case anyone else finds this thread later.

If adaptive idle is positive then the min airflow is too low (i.e. it's increasing timing to help increase output since it's not getting enough air).

If it's negative then it's removing timing / engine output due to too much air.

Sorry about that

edit:

Notice around frame 4740 you're at ~23% TPS, -9* adapt advance and 800 RPM's. The throttle closes down to 20% by frame 5098, adapt goes to basically 0* and RPM comes down to the 725 RPM's being commanded.

Try engine braking sometime and get an idea how low the TPS goes during that.. that should give you an idea what the min airlfow table is commanding. If it's going lower than you usually see at idle, then increase min airflow table.

If it's staying higher than you see at idle (when totally stopped and idle adapt timing close to zero) then min air is too high

It's just what has worked for me.. play around with it. You're already doing better than most "tuners" out there!

Thanks!

Your correction makes more sense to me, and I appreciate the detail. I will try a lower minimum final airflow and see what happens. I don't mind experimenting, I'm just trying to keep the ECU re-writes to a minimum!

[Random84]

I just wanted to update the thread:

I did lower my idle final minimum air table by around 5% and it seemed to reduce the negative idle adapt advance by approximately half. Initial impressions are that it appears to be the issue; I will have to drive more to make sure it's good. Idle speed itself seems to be about the same (725rpm commanded in neutral) - but now my STFT's are markedly rich by around 20-25%!

This was literally from the prior tune, making a change/reflashing and then starting the car up again and engaging 1st gear in the parking lot. I will monitor it for a while before chasing things but that was a big difference in idle fueling!

[schpenxel]

Give it 150-20 minutes of driving and I bet the trim #'s come back down. I see all kinds of weird things right after flashing

[Random84]

Update: minimum idle airflow was the culprit! Everything has been peachy since my last post. Thanks again, Schpenxel.

[schpenxel]

No problem!

[JBZ]

this is a good read,
im having on idle surge...bucking when i have the brake applied but allowing the car to roll forward. this only happens in 1st gear (when i have the shifter in sport mode) and it did not happen before I had the car tuned and have been researching trying to figure it out. keep in mind i have a stock cam so i don't think i should be getting any bucking.

hoping to try your advice schpnexel and help to dwindle my problem down.

[schpenxel]

Yeah def. shouldn't have any bucking with a stock cam.

What mods?

[JBZ]

Yeah def. shouldn't have any bucking with a stock cam.

What mods?

2.4 pulley, ID850's, ARH headers and x pipe, TR7IX's, msd wires and supporting cooling mods.

[schpenxel]

Tune/log of it happening? I'm curious as to what they changed to cause it

[JBZ]

Tune/log of it happening? I'm curious as to what they changed to cause it

I really don't know and am curious myself.

in the log check out frames 77417-78270 and then again at 81900-82675. this is where I have put it in 1st and slightly letting on roll forward and come to a stop to get the surge. and on another note im trying to resolve my KR you will see, so any advice there will be greatly appreciated.

[schpenxel]

Only thing I see done to the idle section is min airflow increased by 1 g/sec. Surprised that would cause the issues you're having though. I'll check log out later.

It's switched to MAF only, SD is disabled totally
MAF table messed with a little bit up top. Changes are small until ~12,000hz
Injector flow rate is a few % under ID's data. I guess he was trying to make it fit? Not real sure. Offset/short pulse adder tables are right
Rev limiters increased to 6800
LTFT's disabled
PE set leaner at low RPM's
High octane spark table is all over the place? Some spots are 15* higher, some places 15* lower than stock (mostly odd/extreme ends of the table)
Low octane spark table is matching high octane table now. Not a fan of doing it that way but a lot of people do.
AFR spark correction zeroed out
IAT spark table has a big section zeroed out
KR decay rate increased quite a bit at high RPM's (5 to 6x factory values). Seems high for me.
Burst KR disabled

Lot of small transmission tweaks, looks like torque converter lockup pretty much disabled for the first couple of gears

Here's a stock CTS-V tune you can compare to

1443633356.hpt

[JBZ]

Only thing I see done to the idle section is min airflow increased by 1 g/sec. Surprised that would cause the issues you're having though. I'll check log out later.

It's switched to MAF only, SD is disabled totally
MAF table messed with a little bit up top. Changes are small until ~12,000hz
Injector flow rate is a few % under ID's data. I guess he was trying to make it fit? Not real sure. Offset/short pulse adder tables are right
Rev limiters increased to 6800
LTFT's disabled
PE set leaner at low RPM's
High octane spark table is all over the place? Some spots are 15* higher, some places 15* lower than stock (mostly odd/extreme ends of the table)
Low octane spark table is matching high octane table now. Not a fan of doing it that way but a lot of people do.
AFR spark correction zeroed out
IAT spark table has a big section zeroed out
KR decay rate increased quite a bit at high RPM's (5 to 6x factory values). Seems high for me.
Burst KR disabled

Lot of small transmission tweaks, looks like torque converter lockup pretty much disabled for the first couple of gears

Here's a stock CTS-V tune you can compare to

1443633356.hpt

thanks for the file, actually it matches my stock file exactly, no differences. weird all the stuff in my tune stuff, I have looked at all the differences but confused on what half of it actually means. let me add that I am not a tuner and am learning and this is a little over my head. what im getting out of your comments are...my tune may be a little screw up? man I don't even know where to start

[schpenxel]

Nothing too crazy, the only weird thing was the high octane timing table changes. Not sure what they had in mind there. I'll try to check out the log tonight