Cold start idle tuning

[Lawso]

Jon,
looking at your datalog, idle goes into closed loop at 44 degrees.
Scalars - Closed Loop Params - Closed loop minimum coolant temperature while idling is set to 44 degrees.
It seems as though as it is commanded to go into closed loop, the target AFR moves to 14.7.
It then drops out of closed loop at 47 degrees.
Could be it realises that the actual commanded afr is less that 14.7 and drops out of closed loop.

If you set the above parameter to 120 degrees, the ecu will not attempt to go into closed loop fueling during idle.
Don't really want closed loop idle with a cam, it wil kick and buck a bit.

Using a monitor, look at target AFR, Wideband and coolant temp.

Alter MAP A: A/F Ratio - Idle A/F ratio vs coolant temperature to get your target AFR to match your wideband.

You can also enable data tracing keep an eye on it as it warms up and adjust it in realime.

Lawso

[Holden202T]

i wouldn't touch the closed loop enable temp, i would change he low rpm 20-100kpa AFR table, i did this with my mates car, commanded 14.0 up till 2400rpm cause when cruising below that rpm with the 286 cam it was surging etc.

also that cam probably wont be happy idling much leaner then 13's!

i've attached the afr tables i used in it.

286 cam idle afr table.jpg (26.87 KiB) Viewed 4240 times

286 cam afr table.jpg (180.7 KiB) Viewed 4240 times

by the way this thing idled with about 65kpa map sensor, and didn't need to change the 20-40kpas for that reason!

[jon]

First of all I just wanted to thank everyone that has been giving me advice on this post. The more input I get the more I can try and understand the brains behind the ecu and its programing.
I made the modifications that Holden202t suggested to both the tables and then recorded another log. But I got similar results from a cold start. At 25 deg coolant temp the target is 12.5 but my wideband is saying 14.8
Its not until the engine gets to 68deg when the target AFR of 13.4 is sort of matched with the wideband
From 68deg to operating temp of about 92deg the AFR starts to swing the other way and richen up until target is 13.6 and wideband is 12.9-13
Is this something I have to just live with or is there a way of fine tuning to get the target AFR and wideband to match all the time?
Also, if closed loop is not needed for idle is it safe to set the temp from 44deg to 120deg to turn it off. In the log I still noticed it tried to force closed loop at 44deg?
Thanks Jon

[jon]

I forgot to add the modified bin
Jon

[jon]

The part I cant get my head around is if the target AFR is 14.7 the ecu uses the narrow band o2 sensor to adjust fueling to achieve this AFR (closed loop)
Any other AFR eg: 13.1 the computer has to guess how much fuel to add to achieve this AFR as it has no sensor to tell the ecu that the engine is actually 13.1?
Is that right? If so what tables or values do I change to get the ecu's guesswork in the ball park?
Jon

[Holden202T]

if you put 14 afr's in the 20-100kpa AFR table it wont go into closed loop at idle, also don't confuse closed loop idle with closed loop fueling! closed loop idle is just the ecm controlling idle rpm, not fueling.

as far as tuning wideband to match commanded AFR this is done via the VE table and should be done when the engine is at operating temp, usually once its right the rest is right.

open loop uses a calculation of commanded AFR, ve and other offsets to work out the amount of fuel to put in, so if ve table is wrong it will always change.

[VL400]

There is some info on how the fuel is calculated when we were discussing MAT loaction here .. https://pcmhacking.net/forums/viewtopi ... p=596#p596

The easist way to do what you want is to adjust the "Inverse Temperature term vs Charge Temperature term" table, can increase the enrichment at lower charge temps - charge temp being based on both coolant and manifold air temps. The table "% Coolant contribution for calculating charge temp Vs RPM & MAP" is more difficult to adjust.

[jon]

When tuning the ve table at operating temp I can get the target AFR and wideband AFR pretty close but when I start the engine from cold the target AFR and wideband can be 2-2.5 points out on the lean side then as the engine gets closer to operating temp the Target and wideband eventually read the same. So I am guessing something definately has to be changed to allow the ecu's calculations of how much fuel should be added to achieve certain target AFR's is closer to the mark.
I had a quick look at the link you sent me VL400 about adjusting charge temp. The bit that still puzzles me is when the engine is cold and off the coolant and MAT temperatures are almost matched but 14 seconds into starting the engine coolant temp is 24deg and MAT is 34deg? Outside temp was about 24deg. I would have thought that outside air (24deg) passing through an intake manifold of about (24deg) would give you an air temp of about 24deg? I wouldn't have thought after 14 seconds of the engine being started from dead cold it would warm the air by 10deg or am I missing something?
If adjusting the calculations affecting charge temp to get the target AFR in the ball park is the answer to my current problem I want to make sure the MAT sensor is reading correctly.
I am almost ready to visit holden to buy a new MAT sensor
Thanks, Jon

[Holden202T]

well i'll be honest i've never given to much worry to cold start being the same as commanded as once i get the ve table right when hot it usually fixes any cold running issues i've had.

i know my 202 is about 6 afr at cold engine start and the target is 5 (methanol) but once its up to temp they are pretty much spot on so i left it at that

the other thing you need to remember with the two sensors ... on a 5ltr, the CTS is at the front of the manifold under the throttle body and the MAT is down near the back of the motor on the edge of the head ..... SOOO there is always less air flow around the manifold at the back, plus the heat coming out of the motor will heat up the coolant in the motor and the MAT sensor but you might not necessarily see this accurately till the thermostat opens.

my 202 has a temp sender at the back of the head and the ecm sender is in the thermostat housing, the difference from front to back is like 20 degrees till the water starts flowing after the thermostat opens ... but then when i had another motor in it that had the rear sender up the front just behind the thermostat housing the two read within a degree or two of each other.

you also have to keep in mind, the MAT on a commodore will be effected by heat soak, one thing i found out when i put the MAT in the 202 vk efi manifold directly behind the throttlebody, reads roughly a few degrees above ambiet when wide open throttle, but then cruise with low throttle openings and the temp starts to climb

[jon]

So another words dont worry about the cold start AFR to much as long as the engine runs ok cold? Maybe Im just looking to much at the wideband readings compared to the target AFR and expecting them to be the same no matter what temp the engine is.