When my engine is at about 60 MAP (and higher I think), and the engine is cold (below about 175 F), I get a lean condition. Lean enough that the engine stumbles, and the WB O2 shows around 18-20 AFR. I have adjusted the AFR at Startup Vs. Coolant Temp table up several times, but it doesn't seem to help. I assume that the number in this table is subtracted, since it has higher numbers for colder temperatures.

The ECU is in closed loop at this time, shouldn't the closed loop logic keep this from happening? When I press the throttle a little farther, it goes into PE mode and immediately goes rich, so that is how I deal with it, but I'd like to fix the problem. Is there another table I need to adjust for this?

Thanks for any help,

John.

 

Does the integrator appear like it's trying to correct that condition? BLMs? Could it be an AE issue?
Maybe your VE is so far off in that area that the ECM can't really compensate.

 

The 747 in oem form relies on a thermactic air cleaner to guarantee a min IAT. Cold or cool engine might just wind up being a little cold blooded.

In looking at a couple bins the TPS PE enables were all at 55-60%, try dropping that to like 45 and see if that doesn't work for you.

 

I currently have PE enable set at 25%. I get the lean condition at about 20% throttle.

My VE table in that area gives me BLMs of about 124-128 when the engine is warm.

I don't have the warm air intake thing at all, in fact I have the dual snorkel air cleaner that also takes air in through cowl induction and I have plugged the two snorkels to make sure the engine gets nice cool air.

The temperature here was only 60 degrees F today, not that cold. Maybe I am going to have to follow your lead, Grumpy, and put this in open loop mode all of the time. Can I solve this by doing that?

 

there isnt a IAT fuel enrichmet table in the 747 ? ill have to investigate this further and get back to you. also on a side not you might wish to put the thing in closed loop at woarmer engine temps.

 

There's no IAT input on the 7747. I'll look into keeping it in open loop longer. I'm not sure how to do that.

I found it. "Min. coolant temp for closed loop fuel". It looks like it is at 19 Deg. C now, I'll raise that and see if it helps.

 

how can this ECM calculate air mass without and IAT to figure out density ? if it doesnt have one thats unreal ! i havent used the 747 for anything so im not the in house expert on it. 19c is about 42 F so id say thats a bit cold for a CL operating temp.id set it for at least 70c

 

The 19 degrees was a bin file on my PC at work. Actually, the car was going into closed loop at 2 deg. C. Meaning, it was always in closed loop. I put it at 60 deg. C, and it didn't help. Guess I need to look at some other tables. I'll set it about 70 deg. C and begin working with some of the other open loop tables. Maybe I can get it right.

And nope, no IAT. It was probably close enough to pass emissions without, and they probably saved a few pennies per car by not having it.

 

there should be an afr vs coolant temp table or something similar. fatten it up. ill dig out my 747 doc's and see what i find.

 

I've tried the AFR vs. Coolant temp before, but with it in closed loop, it may not have had any affect. I'll try it again with it in open loop mode and see if it works better.

 

Possible your O2 sensor causing this, maybe try a heated one. Thats my next mod.

 

I changed the temp at which closed loop becomes active, set it to 75 deg. C., and for some reason it never went into closed loop, even when the temp was well above 80.

Still had the lean condition. Raised the open loop AFR vs. map at those MAP settings, and it only went lean to about 18 instead of pegging my AFR meter. Lowered the open loop AFR vs temperature and it didn't seem to help much.

I'll keep fiddling with it.

 

Is your O2 sensor working? A bad o2 sensor can screw things up like that.

A MAF system does not need an IAT sensor. In a SD system it's used to calculate how much denser the air is when it's cold. In MAF, the MAF does that automatically.