Running a little lean with cold temps
 

Had VE table tuned pretty well, in the WOT regions at least..but now at night when temps are low and my new IC working a lot better than my last... IATs are only rising about 10 degrees over cruise temps doing a 3rd gear pull or something- starting to run a little lean, nothing crazy, but .3-.4 points.

I'm running a MAT correction value of 50%, and the non linear table is zero'd out. I notice Gair in these temps/conditions is only 101% with these cold temps at night. My guess is that it's just not adding enough fuel to compensate for the significant lower temps than what I tuned the VE table at?

Reason I'm using MAT value of 50 is the whole hot start issue...tried to find a good compromise, but now that temps have really dropped seems to be running different. I'm using the given IAT calibration values from DIY auto and brain's pdf... that was the only other source of error I could think of.

Really just wish there was a feature to taper off the non linear MAT correction table with rpm (I understand MS1 had this? as well as Reverant's units)

Any other thoughts?

changed MAT correction factor back to 100 and getting a few percent of Gair back seemed to help a lot without touching VE table...

Turned on EGO at idle, and that really helps with lean starts. Not ideal solution...but working out alright, especially now that Ego steps you can now do in 0.1 steps (I use 0.2) with the new beta firmwares.

I'm also having possible boost/vacuum reading on the MS issues, so who knows, maybe that was playing into all this as well, very likely. Gotta fix my possible hardware issues first

No suggestions Aaron. But, with temperatures now about 60°F cooler than when I fuel tuned, I'm not seeing much variation in AFR. I'm using the default MAT correction factor (100%).

the MS will add fuel when cold by default if the corrections table is zeroed out...

Yeah, I think it just wasn't adding enough for me with the 50 percent correction value. Gair was 101, then with 100 percent, it was 103%, i guess enough to make the difference.

either way I might have a boost/vac leak, so all bets are off until i get that sorted out.

Aaron did you ever get to the bottom of this?

I have a very similar problem, i zero'd out the non linear correction and I am using 75% MAT correction factor and VEA constantly adjusts the map one way in a morning when its cold (leaner) and another way later on in the day when its warmer (richer).

This seems to be the inverse of your problem, so I am wondering if reducing the MAT correction would help me, if this was indeed your end solution.

Yep, I put it back to 100 MAT correction value and it's been pretty good there. Haven't noticed any lean-ness on a really cold night there, so I haven't touched it. I ran 50 MAT correction value all last summer, and temps were pretty consistent I think and I had no issues...it also helps the hot start issue slightly.

Either way I got my VE Table 90 percent there and haven't messed much more with it since I've been busy moving.

Do you have the open element GM sensor and where is it located?

I do indeed use the GM IAT, it is in my IC cold pipe to the TB, but it is in the bay so it does suffer mild heatsoak on a hot start, I am not so fussed about that though as I rarely hot start. From my understanding, it shouldn't affect it much while air is moving through there at a decent rate?

Yeah that's my understanding as well. My sensor is outside the bay- on hot starts the temp reading isn't THAT high..but its still very lean. So maybe something else is at play, and I haven't found a great solution for it yet. I've just been adding a few points to VE in idle area to make it a little richer than ideal, and let EGO lean it out. It helps on hot starts before EGO kicks in (30 sec delay, can't find a way to change it).

Anyways sounds like you might as well try reducing the MAT value to 50, lots of guys use that with no problems. At WOT I doubt it will make much difference either way, the difference between 100 and 50 is usually only about 1 percent fuel