Purpose/goal of warmup timing table

[foliage]

I understand how the warmup timing table works where it kicks in at the min temp and then exists at the max temp, it then uses the timing in the 2D table when in side of these bounds. On a standard RB20det (r32) ecu the timing values seem very retarded around 10 degrees, also oddly only kicks in at 30 degrees so you'll start driving with full timing for a few minutes, then full blown retard ignition causing the turbo to spool, then TP max comes in and kicks it back to full timing again making the car drive like ass.



I simply put values of 25 deg in there with a slope which made it much nicer to drive, I then considered disabling it completely, however this got me asking the question what were nissan trying to achieve with the warmup timing? Is it simply trying to warm the motor up faster by taking a few degrees out of the timing map? If so how much should you take out and if you disabled the map would the longer warmup time make much difference?

Thoughts?



and finally there is this map which also seems to add timing, when is this one accessed?


edit: and how does the after start timing advance table come into play, it looks as though it is adding timing on cold temperatures, do all the maps cumulatively add to the timing for the final number? When datalogging I found that using the stock warmup table I was only getting 7 degrees ignition timing on cold start which makes me think the other two maps were ignored.

[PL]

It's assumed that the table has 7 degrees in it to increase EGT's and get cat to running temperature quickly to help pass emissions. I usually fill it with 20's.

PL

[foliage]

That makes a lot of sense, can anyone comment on how all 3 tables interact together.. cumulative or 1 of 3 are selected based on x condition?

[Matt]

Warmup table is used conditionally within the warmup parameters and other two tables do not come into play

The other two tables are temperature and RPM based to determine timing offset
TADVC TIMING_ADVANCE
Water temperature correction table after startup
BCADV AFTER_START_TIMING_ADVANCE
Rotational speed correction table after starting

Code: Select all

B787 : B6 14 5D 	"  ]"		ldaa	X145D
B78A : CE FE C0 	"   "		ldx	#TIMING_ADVANCE
B78D : BD 80 9F 	"   "		jsr	L809F
B790 : 36 		"6"		psha
B791 : B6 15 44 	"  D"		ldaa	X1544
B794 : CE FB E0 	"   "		ldx	#$AFTER_START_TIMING_ADVANCE	
B797 : BD 80 9F 	"   "		jsr	L809F
B79A : 16 		" "		tab
B79B : 32 		"2"		pula
B79C : 10 		" "		sba

With these two tables:
Timing vs RPM is put into B
Timing vs Temp is put into A
Subtract B from A


Basically value of second table (timing vs RPM) taken from value in first table (timing vs temp), and this is used to offset timing during warm start (when the 'warmup timing' table is not used)

[foliage]

I see so when warmup timing is not used eg starting at > warmup_timing_max_temp, the timing =

a) = (A-B)?
b) = main timing table + (A-B)
c) = main timing table - (A-B)

How long are these two tables used for before the main ignition timing map is used on its own? Or are the warm timing start tables used for ever after start?

The reason I am asking is my timing seems inconsistent, eg I have fixed my cold start timing now so the car drives nice, however when "warm" but not hot it feels like it is missing timing still (I haven't verified with datalogging), I suspect this may be why?

If I was to zero out the timing vs temp map would this increase the "Warm start" timing to be what the main timing map provides?

[Matt]

I believe (b) where added to the main timing. Would need to read the code further

Normally around 85 degC is when these timing maps stop being used (65 degC warm timing)

If you zero out the timing vs temp map it would affect the timing upto 85degC (but not when the 'warm start' timing map is used)

[foliage]

See my car sits around 81 degrees when cruising most days, so it makes a bit of sense why it might be causing issues now.

When completely hot it drives nice, when cold it drives nice, randomly in the middle it feels down on timing.

If you zero out the timing vs temp map it would affect the timing upto 85degC (but not when the 'warm start' timing map is used)

I'm confused, if I zero'd out both maps, wouldn't it be (main_timing + (0-0)) so essentially as if it wasn't being used?

[Matt]

I would think at 0 it would take no effect. I can try it out on the bench if you wish...

[foliage]

I would think at 0 it would take no effect. I can try it out on the bench if you wish...

Only if you have time, I'll try it myself tomorrow anyway see what happens.

Thanks for all the info!

[foliage]

Zero'd the tables out, now when I start the car no matter the temp it drives like it is warm, much much nicer. Imo I would nuke these maps on all tunes unless you specifically need the cat warmed up to pass a test.