lean warm up in OLSD

[truckmann]

I've be noticing my truck runs really lean when warming up. It starts out a little rich as expected (although still leaner than commanded) and then goes to 16-17afr. Then the afr slowly comes back to normal until the ECT is about 170 deg. I have logged using the idle-airflow config several time and used the results to set my Base Running airflow. So what am I missing here.

[Billf6531]

Now that's an interesting question that deserves a response. Try the attached histogram, and post your results.

[truckmann]

Thanks I will do that as soon as I can and post it up.

[5_Liter_Eater]

Do you have and AIR pump? If so check to make sure it's not kicking on. It's job is to inject extra air into the exuahst to keep emissions in line on startup. You can force the AIR pump off in VCM Controls.

If no air pump have you done any MAF tuning? What do your trims look like at idle when it enters closed loop?

[truckmann]

Do you have and AIR pump? If so check to make sure it's not kicking on. It's job is to inject extra air into the exuahst to keep emissions in line on startup. You can force the AIR pump off in VCM Controls.

If no air pump have you done any MAF tuning? What do your trims look like at idle when it enters closed loop?

No Air pump.

MAF is in fail and since I'm running OLSD I don't know what the trims look like but after it is warmed up the AFR error is in the -2% to 0% range.

I don't know if this will give you any additional info but I have attached a couple of my drive to work logs from the past couple of days.

[truckmann]

Now that's an interesting question that deserves a response. Try the attached histogram, and post your results.

I loaded the Histo you provided with the previous log and here is what it looks like.

[5_Liter_Eater]

sorry, missed the SD part.

Looks like its time to start playing with the bias table.

[truckmann]

sorry, missed the SD part.

Looks like its time to start playing with the bias table.

I was thinking the same thing after seeing my afr errors move to the lean side on a drive home log a few days ago when the temp got up into the mid 80's.

I didn't realize that the bias table would be giving me that much error on warm up. Now if there was only a good way to get that thing set up short of trial and error guessing...

[5_Liter_Eater]

There are quite a few threads on it. This seems like a good one. http://www.hptuners.com/forum/showth...highlight=bias

[5_Liter_Eater]

Or if you wanted to take the easy way out you could lean out your OLFA for the colder temps. It's technically "cheating" but if you're not having problems with the AFR error being off as IAT temps change (winter to summer, day to night) with consistent ECTs then it's a quick fix.

[truckmann]

Cool nice thread! I haven't seen that one. I'll read through it in depth later when I have time.

I don't think I can get by with the the cheat method.. since I did noticed about a 4% swing on one particular day from morning to late afternoon when the temps went from 60's to mid 80's.

[Billf6531]

The reason I suggested looking at the OLFA table, is that the idle VE is off quite a bit when the engine is warming up, and well-tuned when warm. I wouldn't attribute the error to it. The bias/filter tables could possibly be improved, but like the referenced thread mentions, it's a bear to get right. The 'cheat' method of attributing the cold warming up error to the OLFA table has the advantage of affecting only a few minutes of running time, until rising engine temp disables it. Try plugging in 50% of the AFR correction and tell us the result.

That said, if you can fine tune the bias/filter tables to account for this, and cause no problems elsewhere, I'm all ears.

I've been testing some changes, and I'm using a linearized version of the C6 bias/filter tables adapted for a C5.

[truckmann]

Thanks. I will try whatever I can to get it where it should be. I will take your suggestion and start out with the OLFA table to get it warming up closer to where it should be since it is going to take me a while to work on the bias.

[truckmann]

I made some adjustment to the OLFA table as suggested and it did reduce the actual AFR along with the commanded so now it is warming up at closer to a reasonable range although the error % is about the same.

I haven't had time to look at the bias yet, but I will keep working on it from as many angles as needed to get it working as it should be.

Thanks for your help and input thus far. I will report back after I get some additional work done.

[5_Liter_Eater]

[EC_Tune]

I created an excel spreadsheet a while back (can't find the dang thing now though!! Arrghh!) where I put in a desired AFR for the coolant temp at hand and compared it to the actual AFR to modify the commanded AFR (OLFA table) so that your actual AFR on warmup is corrected.

That way we take out the "Actual vs Commanded" matching issue which will never be correct on a cold engine because of fuel atomization issues.

[truckmann]

I was just too hung up on the "commanded" part of the equation so after learning to somewhat ignore that I now have it pretty close.

Next issue to deal with is the slight surging and occasional stumble in slow off idle situations. It's starting to drive me nuts and while I have it manageable I would really like to be able to get rid of the problem and I am at a little bit of a loss on what I need to work on to fix it as nothing I have done so far has helped much.