Idle gurus.. come on in..

[Chris81]

Alright, i've gotten my buddy's stroker Vette to drive and run very well.. the only little thing left is fixing the idle dropping when coming to a stop.. it does this and will surge up and down until the car stops.. then hits the idle and thumps perfectly.

The car is autotuned and automafed.. bins are within .02 + -
The car runs in closed loop with LTFT's disabled
Desired Airflow is dailed in with RAFIG
Timing is stock (I haven't adjusted it just yet)
Effective area scaler is at .0320

The car has:

395 stroker
240/244 cam
LS2 TB
FAST 90 intake
SVO 30's (scaled correctly)

I'm assuming its the cracker/follower but where do I start? Airflow? Delay? Decay?

The car was tuned once before and some of these tables were slightly adjusted, but much of it was left stock.

Also, any ideas on airflow with the AC on? What do I change? I haven't had a chance to mess with AC stuff much yet.

This is the last bit for this car to be finished up, and boy was it different than my car.. lol :cheers:

[oztracktuning]

Give it more timing
and match base timing and main spark table.

more airflow at idle at the suspect temps

get it to be richer at idle. Tune it for as smooth afrs as possible near idle.

[Dirk Diggler]

Increase the airflow in the Throttle cracker tables at the MPHs that are affected.

[ringram]

Yep, I vote more cracker airflow too.

[TAQuickness]

third perspective...

the TC & TF longer decay rates and slightly more flow made a night and day difference on my idle transistions.

[Chris81]

Cool guys, i've get it a shot..

Any ideas on what to do with airflow for when the air conditioning is on?? I haven't really looked at it much.

[bink]

Scan with GM.IAC_AC_DMA pid. See how much airflow is added/subtracted on/off AC. Then adjust B4329 and B4328 accordingly.

{B4329} Idle Learn Drive A/C On Limit High.

{B4328} Idle Learn Drive A/C On Limit Low

Here's what mine are at:

B4329 = 4.00 g/sec

B4328 = -.50 g/sec
If you scan with the airflow pids (DMAs) and you get some pretty funky values in the Start Up, Friction etc. pids this will help bigtime. It seems that the PCM will put these "learned" airflow values where there is available memory!!
This made a huge difference in my idle consistency from one start up to the next.

:cheers:
joel

[bink]

third perspective...

the TC & TF longer decay rates and slightly more flow made a night and day difference on my idle transistions.

Has anyone tried reducing the delays (shortening time delay) of these ??? :

{B4503} Filtered RPM Airflow Control Delay
{B4504} Airflow Learning Control Delay
{B4505} Airflow Direct Speed Control Delay
{B4506} Spark Airflow Speed Control Delay


Mine are stock at 1.3 seconds.

[Chris81]

update:

I rechecked the RAFIG and in the trouble temp. the RAF was very close (like +.03 g/s or so)

So far all I did was increase the throttle cracker airflow 20% from 4 to 36 mph at 1000 and 1600 rpm..

I noticed that it got a little better..

Here is the weird thing, the car sometimes will do great.. when the clutch is pressed in it falls right to 950 and stays, other times the idle jumps up and down until I come to a stop.. its very odd that it does this sometimes and works perfect other times.

I've noticed that it does it the worse (when it does it) when i've driven a short distance and pushed the clutch back in or something of that nature (like only shifting from 1st to 2nd for example, like a parking lot)

I still need to up the base timing to around 30 degrees for starters and play will the cracker/follower some more.

I'll keep updating as I go.. maybe others with my problem will benefit from this thread

Thanks,

Chris