Initial Ignition Timing Post Start

td-d · **Posted:** Mon Dec 23, 2013 6:30 am

I was asked by Andy (andya) to look into an issue he's had with post 2008's models (apparently particularly noticeable on the STI's) with ignition timing being highly retarded right after starting, making the engine run and sound awful until ignition is positive again. I'm sure this is part of the barrage of emission related logic used to warm up the catalysts quickly up front. It is also likely that changing this to positive timing will assist with E85 warm up issues as well. There is likely also a decay table which I'll look for.

In any case, here it is for AZ1G202I (USDM 08 Sti):

Code:

   <table type="2D" name="Ignition Timing Post Start" category="Ignition Timing - Advance" storagetype="uint8" endian="big" sizey="16" userlevel="4" logparam="E53">
      <scaling units="Base Ignition Timing (degrees BTDC)" expression="(x*.3515625)-20" to_byte="(x+20)/.3515625" format="0.00" fineincrement=".2" coarseincrement="1" />
      <table type="Y Axis" name="Coolant Temperature" storagetype="float" endian="big" logparam="P2">
        <scaling units="Degrees F" expression="(x*1.8)+32" to_byte="(x-32)/1.8" format="#" fineincrement="1" coarseincrement="5" />
      </table>
      <description>This table retards timing immediately post start.</description>
    </table>

and for the rom xml:

  <table name="Ignition Timing Post Start" storageaddress="CF9A8">
   <table type="Y Axis" storageaddress="CF860" />

Sasha_A80 · **Posted:** Mon Dec 23, 2013 7:09 am

Is it long timing retard or short 300-700ms anti-jerk alike type ?

I see those short deep retards any time after accelerator angle rise from zero ( and logged Idle switch falls to zero) for any MY06+ Hitachi ROM.

Some ROMs have VehicleSpeed dependant retard some ones do not.

td-d · **Posted:** Mon Dec 23, 2013 7:20 am

Well, this one is a straight -20* across all coolant ranges, but there are other tables around that area. Now that you mention it, there is one that has a rolling profile like what you are pointing out...

andya · **Joined:** Sun Nov 02, 2008 4:32 pm **Posts:** 274

A word of caution for those who would automatically zero these values:
I believe this table serves more than just catalyst warmup as observed with our project 07 STi with Mahle (low silicone) drop in pistons. After start, the engine is quiet below +5 degrees then the pistons begin the Hawaian fire dance beat which intensifies to +16 degrees until the engine reaches operating temps. Too much timing during warmup will cause scuffing, but E fuels may react differently.

dux10 · **Joined:** Tue Jun 05, 2012 7:37 pm **Posts:** 81

Good Stuff! :mrgreen:

dux10 · **Joined:** Tue Jun 05, 2012 7:37 pm **Posts:** 81

Sasha_A80 wrote:

Is it long timing retard or short 300-700ms anti-jerk alike type ?

I see those short deep retards any time after accelerator angle rise from zero ( and logged Idle switch falls to zero) for any MY06+ Hitachi ROM.

Some ROMs have VehicleSpeed dependant retard some ones do not.

Are you sure you aren't seeing the effects of overrun ignition timing?

edit: There are 2 tables side by side, one is Timing vs ECT and the other is Timing vs. Engine Speed. Might be what you are referring to. Older ROMs only appear to have the first one.

lach01 · **Posted:** Sat Jan 18, 2014 2:18 am

I'd be very interested if anyone has seen a similar table pre 2008, particularly rom A8DH100M as haven't logged it for a while but on cold start there is a consistent drop in timing of approximately 20 degrees for about the first 60+secs that seems to vary in duration depending on temp. It has made the car consistently stumble under light throttle loads for the first km or so and as mentioned above sound terrible.

andya · **Joined:** Sun Nov 02, 2008 4:32 pm **Posts:** 274

It seems more pronounced with the secondary air equipped models- 06 up.

Sasha_A80 · **Posted:** Mon Jan 20, 2014 4:05 pm

This is after start catalist fast heating.
Rich startup mixture is compensated by secondary air and timing is retarded to speed up catalist preheated and its efficiency raised.

lach01 · **Posted:** Sat Feb 08, 2014 10:33 am

Yes, the timing is retarded so far though that the car struggles under light load and when 50% of it's driving is less than 5mins it means economy is terrible. If anyone knows where the tables are to adjust the amount of timing removed it would be great.

td-d · **Posted:** Sat Feb 08, 2014 1:18 pm

lach01, I think this is it, you'll need to test it:

Code:

ROM:00084B3C Table_Ignition_Timing_Post_Start:.data.w h'10 ; DATA XREF: sub_364A2+336o
ROM:00084B3C                                         ; sub_36834+1Co ...
ROM:00084B3E                 .data.w h'400
ROM:00084B40                 .data.l h'CAA4C
ROM:00084B44                 .data.l byte_CAACC      ; = 2.852
ROM:00084B48                 .float 0.3515625
ROM:00084B4C                 .float -20.0

andya · **Joined:** Sun Nov 02, 2008 4:32 pm **Posts:** 274

Does wonders with warmup in extreme cold temps, no more surging or struggle to maintain idle speed!
Did you manage to locate a decay table? Would like to test timing ramp a little earlier after start.

td-d · **Posted:** Sat Feb 08, 2014 2:07 pm

andya wrote:

Does wonders with warmup in extreme cold temps, no more surging or struggle to maintain idle speed!
Did you manage to locate a decay table? Would like to test timing ramp a little earlier after start.

Haven't really looked, will scratch around.

Sasha_A80 · **Posted:** Sat Feb 08, 2014 4:06 pm

It may be a sum of 3 to 4 decays with a different coolant dependent start value and slope for fuel enrichment plus final correction and probably a similar way for initial throttle openning.

td-d · **Posted:** Sat Feb 08, 2014 11:17 pm

Sasha - I can't download that attachment for some reason...

RomRaider

Initial Ignition Timing Post Start

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