logging iac with efi-live?
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TECH Addict
Joined: Nov 2001
Posts: 2,659
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From: Bellevue, Wa
logging iac with efi-live? what pid is it?
is it idle air control position?
or desired idle air control position?
or other?
I figured it was #1 but when I log it the value is always zero unless I free rev it.
am I logging the right pid? what is the normal behavior I should see? I hear everyone talking about getting their IAC counts to a certain value thus I find it strange mine seem to be zero all the time
is it idle air control position?
or desired idle air control position?
or other?
I figured it was #1 but when I log it the value is always zero unless I free rev it.
am I logging the right pid? what is the normal behavior I should see? I hear everyone talking about getting their IAC counts to a certain value thus I find it strange mine seem to be zero all the time
Idle air control position PID is GM.IAC
Below is in reference to a 98 Fbody.
I connect to the PCM using the Dynamic packet mode as opposed to the 5x24.
There are times when I have used the 5x24 mode that the scanned data just did not look correct. I have no problems with the Dynamic packet mode.
Below is in reference to a 98 Fbody.
I connect to the PCM using the Dynamic packet mode as opposed to the 5x24.
There are times when I have used the 5x24 mode that the scanned data just did not look correct. I have no problems with the Dynamic packet mode.
Just a FYI:
The IAC PID is not a measure of the actual IAC position, there is no sensor to measure that. The IAC PID is the value to which the PCM is commanding the IAC.
To verify the PCM's commanded IAC position try logging the desired IAC position {GM.IACDES}. This value will change in response to changing idle speeds and driving conditions. The IAC cannot be "moved" by the PCM fast enough to keep up with the DESIAC so the PCM commands the IAC to move towards the DESIAC in a controlled manner. Basically the IAC chases the DESIAC.
You could also try logging the {GM.DESIAC_B} PID which is the desired airflow in g/sec that the PCM is requesting through the IAC valve.
Regards
Paul
The IAC PID is not a measure of the actual IAC position, there is no sensor to measure that. The IAC PID is the value to which the PCM is commanding the IAC.
To verify the PCM's commanded IAC position try logging the desired IAC position {GM.IACDES}. This value will change in response to changing idle speeds and driving conditions. The IAC cannot be "moved" by the PCM fast enough to keep up with the DESIAC so the PCM commands the IAC to move towards the DESIAC in a controlled manner. Basically the IAC chases the DESIAC.
You could also try logging the {GM.DESIAC_B} PID which is the desired airflow in g/sec that the PCM is requesting through the IAC valve.
Regards
Paul
TECH Addict
Joined: Sep 2003
Posts: 2,065
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From: Atlanta, GA
if you have surging you should definitely compare the desired iac and actual, and then just compare the IAC actual. If you see like 185 IAC actual, and surging, you might need to tune more, or gasp, drill hole in the tb to a bit larger.
Since its a correction system, if the desired can't control the actual fast enough it will over compensate.
A scenario is this.
in idle, say before closed loop ect temps. (or in gear a4) you will say
see the rpm go to 1100rpm then drop to 800 rpm then go to 1200rpm then go to 700 rpm then go to 1300 rpm then go to 600 rpm then go to 1500 rpm, then drop to 400-500 and stall. This would be an example of poor tuning (timing/cold start enrichment/iac etc). Or maybe just no way for the cam to get enough air in by the IAC.
Efilive pro 6.3 can help by allowing you to force the IAC, timing (relative), and fuel (relative) so you can try out a few things without having to reflash the ecu many times.
You only get so much time before the engine goes to op temps and stabilizes, so it might be a morning ritual to play with. I'm gonna muck around with it soon enough. I do have a little cold start issue, 112lsa cam and a4 with pulley. I'm guessing something is little off, so having some data ready for the tuner (dont have ls1edit) like
"+2 timing when cold helps alot, -whatever fuel" can give the tuner some pre-insight so theres no guessing. Each car of course is different so unless the tuner built your package and tuned it before, its likely the tuner has to adapt to your gear.
In some ways,this is why some of the "package mail tunes" for "package stage" bolt/cams from say TSP might work better. They've probably spend a TON of time fine tuning the little things that bug you, where as if you just threw together a bunch of parts from here or there, there is some tuner "learning" to overcome.
If you think about it, do you really think most tuners are gonna keep your car for a weekend, and range from cold (ice freezing) to 90F temps to get the perfect cold,warm,hot,warm restart(when cold), warm restart(when hot) perfect? That could be alot of time for each unique setup (key word unique).
Of course the better tuners will have a strategy, but it stil takes real world time. The cars heat up fast, then take a while to cool down again.
This is where having your own edit-like software could be advantageous, or just starting with a well known "mod package" and getting a well known "mail tune" then having a tuner (or yourself) fine tune it for maximum power/cold start/warm restart/driveability.
i think the a4's are more difficult than the m6's but i've seen folks with cams and m6's that have the exact same issues (cold start) and those folks have their own copy of edit. so maybe its tuner skill after all.
?? guessing ??
Since its a correction system, if the desired can't control the actual fast enough it will over compensate.
A scenario is this.
in idle, say before closed loop ect temps. (or in gear a4) you will say
see the rpm go to 1100rpm then drop to 800 rpm then go to 1200rpm then go to 700 rpm then go to 1300 rpm then go to 600 rpm then go to 1500 rpm, then drop to 400-500 and stall. This would be an example of poor tuning (timing/cold start enrichment/iac etc). Or maybe just no way for the cam to get enough air in by the IAC.
Efilive pro 6.3 can help by allowing you to force the IAC, timing (relative), and fuel (relative) so you can try out a few things without having to reflash the ecu many times.
You only get so much time before the engine goes to op temps and stabilizes, so it might be a morning ritual to play with. I'm gonna muck around with it soon enough. I do have a little cold start issue, 112lsa cam and a4 with pulley. I'm guessing something is little off, so having some data ready for the tuner (dont have ls1edit) like
"+2 timing when cold helps alot, -whatever fuel" can give the tuner some pre-insight so theres no guessing. Each car of course is different so unless the tuner built your package and tuned it before, its likely the tuner has to adapt to your gear.
In some ways,this is why some of the "package mail tunes" for "package stage" bolt/cams from say TSP might work better. They've probably spend a TON of time fine tuning the little things that bug you, where as if you just threw together a bunch of parts from here or there, there is some tuner "learning" to overcome.
If you think about it, do you really think most tuners are gonna keep your car for a weekend, and range from cold (ice freezing) to 90F temps to get the perfect cold,warm,hot,warm restart(when cold), warm restart(when hot) perfect? That could be alot of time for each unique setup (key word unique).
Of course the better tuners will have a strategy, but it stil takes real world time. The cars heat up fast, then take a while to cool down again.
This is where having your own edit-like software could be advantageous, or just starting with a well known "mod package" and getting a well known "mail tune" then having a tuner (or yourself) fine tune it for maximum power/cold start/warm restart/driveability.
i think the a4's are more difficult than the m6's but i've seen folks with cams and m6's that have the exact same issues (cold start) and those folks have their own copy of edit. so maybe its tuner skill after all.
?? guessing ??
