Idle Ignition Timing

Easty · **Posted:** Thu May 23, 2013 10:52 am

I've had an issue with the way my car idles practically since it was new, rpm bounces and oscillates (-+100rpm) and it feels quiet rough almost like its dropping a cylinder intermittently.

I noticed in a log that ignition timing was also bouncing around (-+1.5deg) and all other parameters appeared to be relatively consistent.

This prompted me to take a look at the logic behind Idle Timing I found one thing of interest. Base Timing Minimum doesn't really form the minimum, the result from the Idle Base Timing tables is compared to the result of Base Timing Minimum table and the lowest of the two values is used. So if base timing is less than base timing min then base timing will be used. If base timing is greater than base timing min Base Timing min is used. Obviously this is not the cause of my issue but the name of this table really needs to be reviewed as it is misleading.

I suspect there is some kind of compensation causing my timing to jump around...

Thoughts?

throttlehappy · **Posted:** Thu May 23, 2013 2:03 pm

Easty wrote:

I've had an issue with the way my car idles practically since it was new, rpm bounces and oscillates (-+100rpm) and it feels quiet rough almost like its dropping a cylinder intermittently.

I noticed in a log that ignition timing was also bouncing around (-+1.5deg) and all other parameters appeared to be relatively consistent.

This prompted me to take a look at the logic behind Idle Timing I found one thing of interest. Base Timing Minimum doesn't really form the minimum, the result from the Idle Base Timing tables is compared to the result of Base Timing Minimum table and the lowest of the two values is used. So if base timing is less than base timing min then base timing will be used. If base timing is greater than base timing min Base Timing min is used. Obviously this is not the cause of my issue but the name of this table really needs to be reviewed as it is misleading.

I suspect there is some kind of compensation causing my timing to jump around...

Thoughts?

Not really misleading since the four 'Base Timing Minimum' is a global minimum that affects off idle as well(gear change)
Idle Base Timing has the RPM component due to cold idle having higher base idle speeds

Also, the idle jumping around on timing is unlikely to be a compensation issue, it typically a crank angle sensor pulse limit. ECU is seeing the individual crank pulses oscilliating as the crank goes past TDC

Heide264 · **Joined:** Sat May 07, 2011 3:22 pm **Posts:** 144

Easty wrote:

I've had an issue with the way my car idles practically since it was new, rpm bounces and oscillates (-+100rpm) and it feels quiet rough almost like its dropping a cylinder intermittently.

I noticed in a log that ignition timing was also bouncing around (-+1.5deg) and all other parameters appeared to be relatively consistent.

This prompted me to take a look at the logic behind Idle Timing I found one thing of interest. Base Timing Minimum doesn't really form the minimum, the result from the Idle Base Timing tables is compared to the result of Base Timing Minimum table and the lowest of the two values is used. So if base timing is less than base timing min then base timing will be used. If base timing is greater than base timing min Base Timing min is used. Obviously this is not the cause of my issue but the name of this table really needs to be reviewed as it is misleading.

I suspect there is some kind of compensation causing my timing to jump around...

Thoughts?

FWIW, I have found the same issue. My idle base timing does not seem to reflect what I actually get at idle.

My idle is pretty crappy as well. I see the small variations you do, as well as some very large ones (it actually will cut to -4 degree advances time to time). I believe this is closely tied to the "Idle airflow" tables. I have been wanting to play around with them a bit, but the descriptions are a bit vague and I haven't had the time to really mess with them.

td-d · **Posted:** Thu May 23, 2013 8:18 pm

There are ignition idle compensation tables - based on load change, and in and out of 'normal' error range.

td-d · **Posted:** Thu May 23, 2013 8:19 pm

AZ1G101N

Code:

ROM:00085494 Table_Ign_Timing_Comp_Idle_Target_Out_of_Error_Range_A:.data.w 9
ROM:00085494                                         ; DATA XREF: sub_384D0+2EEo
ROM:00085494                                         ; ROM:off_388A0o
ROM:00085496                 .data.w 3
ROM:00085498                 .data.l flt_D04CC
ROM:0008549C                 .data.l flt_D04F0
ROM:000854A0                 .data.l byte_D04FC      ; = -2.031
ROM:000854A4                 .data.l h'4000000
ROM:000854A8                 .float 0.15625
ROM:000854AC                 .float -20.0
ROM:000854B0 Table_Ign_Timing_Comp_Idle_Target_Out_of_Error_Range_B:.data.w 9
ROM:000854B0                                         ; DATA XREF: sub_384D0+2F2o
ROM:000854B0                                         ; ROM:off_388A4o
ROM:000854B2                 .data.w 3
ROM:000854B4                 .data.l flt_D0518
ROM:000854B8                 .data.l flt_D053C
ROM:000854BC                 .data.l byte_D0548      ; = -2.031
ROM:000854C0                 .data.l h'4000000
ROM:000854C4                 .float 0.15625
ROM:000854C8                 .float -20.0
ROM:000854CC Table_Ign_Timing_Comp_Idle_Target_In_Error_Range_A:.data.w 9
ROM:000854CC                                         ; DATA XREF: sub_384D0+310o
ROM:000854CC                                         ; ROM:off_388ACo
ROM:000854CE                 .data.w 9
ROM:000854D0                 .data.l flt_D0564
ROM:000854D4                 .data.l flt_D0588
ROM:000854D8                 .data.l byte_D05AC      ; = -1.562
ROM:000854DC                 .data.l h'4000000
ROM:000854E0                 .float 0.15625
ROM:000854E4                 .float -20.0
ROM:000854E8 Table_Ign_Timing_Comp_Idle_Target_In_Error_Range_B:.data.w 9
ROM:000854E8                                         ; DATA XREF: sub_384D0+314o
ROM:000854E8                                         ; ROM:off_388B0o
ROM:000854EA                 .data.w 9
ROM:000854EC                 .data.l flt_D0600
ROM:000854F0                 .data.l flt_D0624
ROM:000854F4                 .data.l byte_D0648      ; = -1.562
ROM:000854F8                 .data.l h'4000000
ROM:000854FC                 .float 0.15625
ROM:00085500                 .float -20.0
ROM:00085504 Table_Ign_Timing_Comp_Idle_Target_Load_Change_A:.data.w 9
ROM:00085504                                         ; DATA XREF: sub_384D0+33Co
ROM:00085504                                         ; ROM:off_388B4o
ROM:00085506                 .data.w 2
ROM:00085508                 .data.l flt_D069C
ROM:0008550C                 .data.l flt_D06C0
ROM:00085510                 .data.l byte_D06C8      ; = 0.0
ROM:00085514                 .data.l h'4000000
ROM:00085518                 .float 0.15625
ROM:0008551C                 .float -20.0
ROM:00085520 Table_Ign_Timing_Comp_Idle_Target_Load_Change_B:.data.w 9
ROM:00085520                                         ; DATA XREF: sub_384D0+340o
ROM:00085520                                         ; ROM:off_388B8o
ROM:00085522                 .data.w 2
ROM:00085524                 .data.l flt_D06DC
ROM:00085528                 .data.l flt_D0700
ROM:0008552C                 .data.l byte_D0708      ; = 0.0
ROM:00085530                 .data.l h'4000000
ROM:00085534                 .float 0.15625
ROM:00085538                 .float -20.0

Easty · **Posted:** Fri May 24, 2013 4:48 am

throttlehappy wrote:

Not really misleading since the four 'Base Timing Minimum' is a global minimum that affects off idle as well(gear change)

I'm sorry don't agree for example if I set 15 degrees base timing and 17 degrees base min timing then base idle timing will equal 15 degrees. If I set base timing to 19 degrees and set base min timing to 17 then idle base timing will be capped at 17 degrees.

This table forms an upper limit not a lower limit, unless I'm missing something :roll:

throttlehappy wrote:

There are ignition idle compensation tables - based on load change, and in and out of 'normal' error range.

Stumbled upon these tables in my rom last night but I haven't looked at the logic behind them yet.

Heide264 wrote:

My idle is pretty crappy as well. I see the small variations you do, as well as some very large ones (it actually will cut to -4 degree advances time to time). I believe this is closely tied to the "Idle airflow" tables. I have been wanting to play around with them a bit, but the descriptions are a bit vague and I haven't had the time to really mess with them.

Which tables are you referring? to the decel tables found by td-d or the target tables found by me?

td-d · **Posted:** Fri May 24, 2013 6:32 am

Easty wrote:

Stumbled upon these tables in my rom last night but I haven't looked at the logic behind them yet.

This is what they look like:

Doing exactly what you seem to be talking about - depending on the extent of the overshoot past the idle target, and the direction and rate of the engine speed fall or rise, will either increasingly add or remove ignition timing.

Easty · **Posted:** Fri May 24, 2013 6:40 am

These compensations are very aggressive given the scaling is so fine, I think I'll have a play with these and see if it helps.

td-d · **Posted:** Fri May 24, 2013 7:50 am

The load related table specifically deals with when there is a rapid change in load - based on increased electrical output, for example - a number of switches are referenced in the logic, including the defogger switch.

dschultz · **Posted:** Fri May 24, 2013 1:52 pm

Easty wrote:

throttlehappy wrote:

Not really misleading since the four 'Base Timing Minimum' is a global minimum that affects off idle as well(gear change)

I'm sorry don't agree for example if I set 15 degrees base timing and 17 degrees base min timing then base idle timing will equal 15 degrees. If I set base timing to 19 degrees and set base min timing to 17 then idle base timing will be capped at 17 degrees.

This table forms an upper limit not a lower limit, unless I'm missing something :roll:

Does this help?
viewtopic.php?f=15&t=9064&start=14

Easty · **Posted:** Fri May 24, 2013 10:50 pm

Yes it does confirms what the logic is telling me!
Thanks

Attachment:

Untitled.png

td-d · **Posted:** Sun May 26, 2013 9:18 am

I have uploaded templates for all 6 tables to Github.

You will need the revised 32BITBASE.xml

Easty · **Posted:** Sun May 26, 2013 11:29 am

td-d wrote:

I have uploaded templates for all 6 tables to Github.

You will need the revised 32BITBASE.xml

Hey Mate did I get this right?

Attachment:

Untitled.png

td-d · **Posted:** Sun May 26, 2013 11:35 am

Easty wrote:

Hey Mate did I get this right?

I'll check tonight when I'm near my PC - quite easy to discern between the 'in range' to out range tables, sine the y axis is a different parameter.

td-d · **Posted:** Sun May 26, 2013 4:49 pm

Looks like you have the out of error range and electrical load tables swapped around (at least that's the way logic leads on the AZ1G101N).

RomRaider

Idle Ignition Timing

Who is online