More idle table questions (answer and win a smiley)

[QUICKSILVER2002]

I have a slightly annoying idle problem from time to time and I want to finally understand how all the idle tables work.

I think most of my confusion is caused by the adaptive idle routines (I sure hope someone put PIDS for this in the scanner soon, hint hint hint... we could really use this)

Ok, so is it true that the adaptive idle routines stop working when the throttle cracker is enabled {B4311}? I've read somewhere that the long term idle correction is still in effect, but I'm just not sure.

Also, what does {B0107},{B0108} really do. (Max TP/Speed for idle mode) The documentation says all airflow calcs will be done in non-idle if conditions are above these parameter values. I think these values are both 0 from the factory, so it is pretty confusing. I think idle is the most confusing term when it comes to tuning an ls1. It is used all over the place, but means many different things.

I still don't have a clear understanding of the IAP table. Can anyone explain how it works under the covers? I've heard vary conflicting info about this table. The stock values are also pretty crazy (19 g/s with a 104*F/40*C IAT). Is parked all the way open? So is it the amount of airflow based on {B2201} - Default IAC parked Position (usually 310/320 steps). That would make sense, but how is it used (if at all).

I have a final question about the idle fuel trim cells 19... (What triggers those cells?). Is there something that says x TP% and RPM = idle FTC... Is there a parameter somewhere? The other FTCs are easy to see in the RPM and MAP boundaries, but the idle thing has always thrown me off.

It is amazing how complex something as simple as idle is. All the other tuning seems so simple to me, but this stuff is tricky.

[Dirk Diggler]

I am with you on idle giving me the most problems but i think i have figured most of it out hopefully

[SSpdDmon]

I have a final question about the idle fuel trim cells 19... (What triggers those cells?). Is there something that says x TP% and RPM = idle FTC... Is there a parameter somewhere? The other FTCs are easy to see in the RPM and MAP boundaries, but the idle thing has always thrown me off.

I think I remember seeing this part in the Engine>Fuel>Trim>Parameters menu. Can't be sure though...at work right now.

[QUICKSILVER2002]

I have a final question about the idle fuel trim cells 19... (What triggers those cells?). Is there something that says x TP% and RPM = idle FTC... Is there a parameter somewhere? The other FTCs are easy to see in the RPM and MAP boundaries, but the idle thing has always thrown me off.

I think I remember seeing this part in the Engine>Fuel>Trim>Parameters menu. Can't be sure though...at work right now.

There is {B4103 - closed loop idle TP} in the 02 section, but I think that is just related to how the STFT work at idle.

[QUICKSILVER2002]

Ok, still no answers. I've been trying some things and so far I have concluded that the IAP table does nothing while the car is stitting at idle If someone has had other results and can explain that would be great.

The car did seem to run a bit worse on trasitions as I played with the table, but nothing was clear.

[bink]

Ok, still no answers. I've been trying some things and so far I have concluded that the IAP table does nothing while the car is stitting at idle If someone has had other results and can explain that would be great.

The car did seem to run a bit worse on trasitions as I played with the table, but nothing was clear.

IAP- The amount of air the IAC flows maximally for a given IAT range (310 steps for me).
Increasing the IAP value indicates more airflow and thus PCM will reduce in it's compensation. Like IFR table.

The closer the IAP/IAC values are to MAF/Dynamic Airflow the better idle and idle transitions will be (as a consequence idle spark also). A "good" VE table is critical.

There is an IAC/IAP value that is added to the Idle routine.

FWIW.

[QUICKSILVER2002]

Ok, still no answers. I've been trying some things and so far I have concluded that the IAP table does nothing while the car is stitting at idle If someone has had other results and can explain that would be great.

The car did seem to run a bit worse on trasitions as I played with the table, but nothing was clear.

IAP- The amount of air the IAC flows maximally for a given IAT range (310 steps for me).
Increasing the IAP value indicates more airflow and thus PCM will reduce in it's compensation. Like IFR table.

The closer the IAP/IAC values are to MAF/Dynamic Airflow the better idle and idle transitions will be (as a consequence idle spark also). A "good" VE table is critical.

There is an IAC/IAP value that is added to the Idle routine.

FWIW.

Bink, this is the best info that I have seen so far. You win the smiley.

So the table defines the amount of airflow at the default parked position of the IAC (310 steps for me also). I suspected this, but was not sure.

I’m still a little confused about some of your statements. When you refer to “IAC” do you mean the IAC effective area table, dle Air Control in general, or the Idle Airflow(RAF) table?

I’m trying to understand what increasing/decreasing the value would do with all other things being constant and close to realistic. What should happen if I raise the IAP? You mention that it will reduce its compensation. So does this mean that the desired IAC airflow will reduce overall?

You also mention, "There is an IAC/IAP value that is added to the Idle routine". Do you literally mean IAC divided by IAP. If so, what is IAC. Sorry for being so confused, but all these acronyms are throwing me off.

Again, I think all the confusion surrounds the adaptive stuff that we cannot see with EFI Live. I change the table and see no running impact in my scans, but that is most likely because the adaptive stuff is taking over and covering up my changes in the majority of conditions.

[hpcubed]

While we are on the subject, the corvette has no IAC valve, so what are those values controlling?

[QUICKSILVER2002]

The idle routines come up with a desired airflow. This is then traslated to mm squared. This value is then sent to the Electronic Throttle Contol routines on corvettes (IAC motor routines on F-bodies...). The effective area table is used on cars with an IAC to convert the area into IAC steps. ETC has a single value conversion from area to TP.

I got most of the above info from a collection of info I have been collecting from different posts. I think it came from someone at HP tuners.

[hpcubed]

The idle routines come up with a desired airflow. This is then traslated to mm squared. This value is then sent to the Electronic Throttle Contol routines on corvettes (IAC motor routines on F-bodies...). The effective area table is used on cars with an IAC to convert the area into IAC steps. ETC has a single value conversion from area to TP.

I got most of the above info from a collection of info I have been collecting from different posts. I think it came from someone at HP tuners.

Ok, I am still a bit confused. First, from your above statement, it would seem that the IAC effective area table is not used on corvettes since there is no IAC motor to step?

Second, how does the idle airflow effect the idle speed (or quality). You can set the desired idle speed to a certain value, the computer tries to maintain that idle speed. I have changed the idle air control values in the bi-directional controls and did not see any effect on idle quality or rpm. Is the idle air flow (or idle air control) doing anything on a corvette?