A question on 12P when cold

[Charlescrown]

Just wanting to understand the Map A A/F ratio initial offset vs coolant temp. Does it add the number to the cold A/F ration map if so for how long? The reason I ask is my car runs quiet rich on startup for a few minutes but leans out to 14:1 where it should be as it warms up. The cold A/F map says it should be 13.5:1 but the wideband shows around 10:1.

[Dylan]

Cold afr's turn off after 44 deg on the V8 tune from memory. Think there's a scaler for that.
When watching a log or real time the target afr will reflect the add on afr after start up.
There's also a table with the decay time in seconds for the add on afr.

[Charlescrown]

That may be what I am looking for do you know exactly what it is called because I see IAC decay but I don't have an IAC connected so maybe its another setting.

[Dylan]

Map X initial run af ratio vs coolant. Gets added onto the 20 100 kpa table. (hot or cold)
Af ratio run af time out interval vs coolant. Is how long the add on afr decays over in seconds.

The target afr displayed on the data dash will reflect the add on value from the afr table.

[Jayme]

I spoke to VL400 about this a while ago. this is a problem in the GM v6 tunes as far as I have been able to tell.

here is part of our conversation.

I would start by using the higher temp cells from the V8 cal in the table "A/F Ratio - Run A/F Time-Out Interval Vs Coolant Temp". The V6 one is pretty slow and can see that in the 6 odd seconds between each AF step.

The starting target AFR of 9.5 checks out, 3.5 points richer than the target 13 from the table. The speed at which this offset decays uses the item "Run A/F Param - A/F Time out decay multiplier" and the interval above. So it starts at 9.5, waits 6.38 seconds, does a step to 86% of the initial offset (3.5 * 0.86 = 3, target should then be 10 which it is), waits another 6.38 seconds, and another 86% step.... and so on. With the time out interval so high this is going to take ages.

so in short... the V6 takes ages even after hot start, to come back to normal AFR. copying the values out of the v8 CAL for "A/F Ratio - Run A/F Time-Out Interval Vs Coolant Temp". helps lots and lots.

I had a look through some v6 cals and I found that Factory $12 BLCD and BKCY have the same problem. BFFH has sane values more like the v8 cal. also APNX $5D in the VN is fine. BLCD is the v6 cal that $12P is based on.

[Dylan]

Thats interesting. Ive never tuned a V6 in real time yet. But the V8 does get to it's normal afr table values quiet quickly after a start up.

[Jayme]

look at v8 vs v6 cal... the v8 on a hot start, starts at an offset of 1 AFR and decays that to 86% every 1 second... less than 10 seconds, and its back to normal AFR.

a v6 cal hot starts at a 3.5 offset and decays to 86% every 6.3 seconds... it takes a few minutes to get back to normal!!

v6 cal.JPG (49.72 KiB) Viewed 8124 times

v8 cal.JPG (51.36 KiB) Viewed 8124 times

[vlad01]

This might explain my my VP runs like shit on cold start up for around 20 sec after using 12P. Looking at that table I'd be starting around the -4 to 8º mark from cold everyday.

[Jayme]

these tables exists in 5D tunes too. you could check out a 5D tune to see how close it is to these values. the main point is that in these few $12 v6 cal's the hot start around 92-104 cells are stupid.

[vlad01]

And thats exactly what I did today, copied the V8 time table and copied the offset from 68º onward over and its it came to target ARF really quick. Will find out if it helps tomorrow with a cold start.