MAF tuning, AFR error doesn't change fuel trims do

[Jason B]

Not sure whats going on, I set up a maf tuning calibration, drive, paste special by half, 3 times using two different methods. The AFR error never changes but the fuel trims do after pasting the maf frequency table. It all says the AFR error should be close to zero. Mine stay mostly the same but the fuel trims go from lean to way rich.

So how do you know when your maf is calibrated? Whose tutorial is correct?

Used this https://www.google.com/url?sa=t&rct=...8zlaK2xxubWnvA

And This One: http://www.silveradoss.com/forums/to...he-maf-sensor/

This is for a rebuilt 5.3, 02 LS1 cam, headers, air intake. Otherwise stock spec Gen IV long block with LM7 intake, injectors, accessories, etc. 2002 silverado programming.

Attached are three scans, flashed for maf tuning, then a fourth with the maf corrections changed in the main file and flashed into the truck. Two sets, two different methods.

[dermotw]

Set the 3 MAF DTCs to fail on first error, if you didn't already... (P101,102,103). Check the LTFT's are reset to 0 as well, btw.

-D

[Jason B]

Set the 3 MAF DTCs to fail on first error, if you didn't already... (P101,102,103). Check the LTFT's are reset to 0 as well, btw.

-D

You set the MAF dtc's to fail when you're calibrating the MAF? I think thats for VE tuning, you can't disable the maf if you're trying to calibrate (tune) it.

[2xLS1]

If you are trying to tune the MAF with a wide band and A/F error it should be in open loop with no fuel trimming. If you are having furl trims effect it it sounds like you are in closed loop with fuel trimming.

[Jason B]

If you are trying to tune the MAF with a wide band and A/F error it should be in open loop with no fuel trimming. If you are having furl trims effect it it sounds like you are in closed loop with fuel trimming.

Seems the stft's are enabled on this truck tune. I didn't disable them. It was in open loop. Guess it time to try again.
Thanks for your reply.

[dermotw]

Set the 3 MAF DTCs to fail on first error, if you didn't already... (P101,102,103). Check the LTFT's are reset to 0 as well, btw.

-D

Oops suffering from advanced brain fade, I meant "force open loop" really!! Heres typical way;

OL & CL – Closed Loop Closed Loop Enabled – select all, set to max
Engine – Airflow – Dynamic Air – Steady State – Hi/Lo RPM Thresh set to 0
DISABLE & RESET YOUR HIGH/LOW FUEL TRIMS LTFT/STFT
DISABLE DFCO
OL & CL – EQ Ratio values to 1 if desired

-D

[Jason B]

Oops suffering from advanced brain fade, I meant "force open loop" really!! Heres typical way;

OL & CL ? Closed Loop Closed Loop Enabled ? select all, set to max
Engine ? Airflow ? Dynamic Air ? Steady State ? Hi/Lo RPM Thresh set to 0
DISABLE & RESET YOUR HIGH/LOW FUEL TRIMS LTFT/STFT
DISABLE DFCO
OL & CL ? EQ Ratio values to 1 if desired

-D

I did just this and not getting any consistent results. I can make a run, copy the average afr error by half to the maf table and the numbers change erratically. Like I'll get a few .07's a few 2.1's, a few 7.5's, etc. Then I do it again and get the same thing, small to large numbers all at random places. There could be a .07 where there was a 11.3 or a 15.6 where there was a -.09, etc.

I'm having better luck leaving the fuel trims enabled and manually subtracting the high positive ltft numbers from the corresponding cell in the maf table. I've got most of the ltft's to +2 to -5 so far. Not really sure if I have to mess with it any more....

This is my unfinished hack job. Not much different than the truck it came off of except for the filter and one less 90.

[dermotw]

Hmm seems odd that it varies that much, of course it does vary somewhat, but that sounds a bit high unless you are seeing e.g. the DFCO/overrun data at the low end, or perhaps the graph itself somehow 'off' (not enough cell counts maybe? or accidentally set to show max or min not average??). I usually use 20 hits as a minimum but some people use 50+..

My own experience, if that means anything, has been that the MAF is quite stable/repeatable until you get down to the 1-2% area, the AE table much less so, it can change depending on the weather etc...

Still, if the LTFT is down under 5% then imho it's pretty much ok...

[jimmyblue]

Long trims roll up way too much random crap / history. Short
trims are not that much better. Especially if your fuel trim cell
covers a wide range of RPM (like stock 4th gen F-bodies) the
averaged trim bears no relation to any particular MAF (or VE)
table cell, just weighted toward wherever you spent the most
time.

If you're trying to dial it in, do it "bare" - no trimming, etc. -
and might also try to make the MAF airflow mode cut in early
(stock, MAF-only above 4K RPM, "blended" VE+MAF dynamic
airflow below that, in a changing balance I gather). So the
changes you make to the MAF table at the low end are only
partially changing AFR, and changes you make to hit a goal
may be "over the top" (as part of the sum, you didn't touch,
so maybe you add 2X the real correction needed, if the MAF
"contribution" to dynamic airflow at the point in question was
50% of the total air mass quantity).

This is why you fault out the MAF for SD tuning, to keep it
from messing. The converse would be true for MAF tuning,
if your VE table wasn't dead-nuts beforehand. But running
MAF only at low flows is probably going to be laggy / prone
to overshoots / undershoots on pedal transients. This lag
can also be a problem for tuning, MAF is always a bit late
(see this, in how AFR changes between gears for same RPM
and MAP) and you want to find places among all the garbage
data, where it's reliable enough to be worth acting upon.
That means high gear pulls (and maybe you have to change
your A4 shift table to keep in high gear at high pedal, if you
are trying to do "road tuning" or a full RPM range dyno pull).