Actual AFR during cold idle

[joecar]

My VE table is dialed in (BEN's AT 1.00 in most places);
during cold idle, my actual AFR is leaner than commanded, and then slowly converges as engine warms up;
What tables are involved here, how do I explain this...?


http://img291.imageshack.us/img291/1527/idle0000ee8.png


BEN map of the above log:
http://img135.imageshack.us/img135/945/idle0001gu4.png



BEN map after warmup:
http://img152.imageshack.us/img152/2910/ve0000kx7.png
http://img135.imageshack.us/img135/8635/ve0000vc0.png

[carneb]

My car does the same. I'dlike to know the answer too. :D

[Tordne]

All ours do it :). In the custom OS3 & 5 I use the A0008 table to command richer mixture till partially warmed up (50*C). You may also be able to do the same by slowing the decay of general after-start enrichment.

Bear in mind that your WBO2 sensor may also not be up to temp straight away and could account for the leanness also, I certainly see that.

[TAQuickness]

This a long standing problem/mystery for SD.

http://www.ls1tech.com/forums/showthread.php?t=478934&highlight=lean

Don't think it was ever resolved either.

[ringram]

Why worry? As mentioned mine is the same too. I noticed yours looked good Tordne in your logs. I might mess with A008 though as when cold it runs a little gutless.

My logs show a sudden drop, not a gradual richening like that. Ill dig one out to show you.

[TAQuickness]

I believe you will find the IAC steps follow the same slope as the richening. My theory is the fueling doesn't account for the startup and startup friction airflow unless it's observed by the MAF (MAF guys don't seem to have this problem).

[ArKay99]

I had this problem at first too, I run an MAF. I found that if I turn off my A.I.R. to log cold AFR, That fixed my cold lean AFR issues. I was seeing 17:1 or more on my WB.

[Dirk Diggler]

Most of these guy have allready gotten rid of the AIR Pump

[TAQuickness]

Yes, my AIR pump has been on my bench for a while now.

Spare PCM inputs ;)

[joecar]

Yes, my AIR pump has been on my bench for a while now.

[joecar]

Spare PCM inputs ;)And outputs.

[ArKay99]

You mean they aren't EPA compliant? :D Think I'll take mine off this weekend too then.:rockon:

[TAQuickness]

Joe - I did a little more intensive logging this morning. The leaness appears to be directly related to the start up friction and start up airflow.

Since we filter out cells less than normal ECT (typically 180* F and less), none of the start up airflow is accounted for in the VE table. Not to mention startup airflow is only there for a short time and if accounted for in the VE table, would throw off hot idle.

But, the MAF reports this extra airflow and it's accounted for.

I'll be tweaking in the realm of {B3632}, {B3628}, & {B3650} for this afternoons drive.

[joecar]

Joe - I did a little more intensive logging this morning. The leaness appears to be directly related to the start up friction and start up airflow.

Since we filter out cells less than normal ECT (typically 180* F and less), none of the start up airflow is accounted for in the VE table. Not to mention startup airflow is only there for a short time and if accounted for in the VE table, would throw off hot idle.

But, the MAF reports this extra airflow and it's accounted for.

I'll be tweaking in the realm of {B3632}, {B3628}, & {B3650} for this afternoons drive.TA, good info, I'll take a look at these.

[SSpdDmon]

Am I understanding {B3632} correctly? Let's say I'm commanding a 12.0:1 AFR for a given ECT right after startup (aka EQ=1.22). If the corresponding cell in {B3632} is 0.5, should my wideband read an AFR of 12.5:1 (aka EQ=1.17)?

Is there a reason we would want to subtract these values from the commanded EQ to lean out the mixture after startup?

Why not just command the values in the Open Loop Fueling to start with?

[joecar]

Am I understanding {B3632} correctly? Let's say I'm commanding a 12.0:1 AFR for a given ECT right after startup (aka EQ=1.22). If the corresponding cell in {B3632} is 0.5, should my wideband read an AFR of 12.5:1 (aka EQ=1.17)?

Is there a reason we would want to subtract these values from the commanded EQ to lean out the mixture after startup?

Why not just command the values in the Open Loop Fueling to start with?I was wondering this too... I thought it would have been added if using EQ units.

[TAQuickness]

Am I understanding {B3632} correctly? Let's say I'm commanding a 12.0:1 AFR for a given ECT right after startup (aka EQ=1.22). If the corresponding cell in {B3632} is 0.5, should my wideband read an AFR of 12.5:1 (aka EQ=1.17)?

Is there a reason we would want to subtract these values from the commanded EQ to lean out the mixture after startup?

Why not just command the values in the Open Loop Fueling to start with?

Commanding the desired EQ in open loop fueling would probably work to, but I'm on OS5 (MAP vs RPM not MAP vs ECT).

Also, once the startup airflows have expired, your AFR's should line up closely with commanded. There will still be a slight varience as you work your way thru B4307. But this varience should be small enough to live with.

From the descriptions, the tables mentioned above should provide the fueling required to get thru the startup airflows.

If your EQ at startup is 1.00 and you need 1.07 to get thru the start up flows, I you would put -.07 in those tables. Would look like 1.0 -(-0.07) = 1.07

I'll let you know how it goes in about 2 hours.

[TAQuickness]

Show me the money BABY!

It will take a bit more tweaking to get the decay rate's down, but it worked and worked well.

[joecar]

...Is there a reason we would want to subtract these values from the commanded EQ to lean out the mixture after startup?...
I was wondering this too... I thought it would have been added if using EQ units.
...If your EQ at startup is 1.00 and you need 1.07 to get thru the start up flows, I you would put -.07 in those tables. Would look like 1.0 -(-0.07) = 1.07...Ah, ok, subtract the negative, can do. :cheers:

[TAQuickness]

Ah, ok, subtract the negative, can do. :cheers:


Forgot to mention, negative values made a leaner condition. I had to go back and make all my values positive.