MAF issues

[Aloicious]

Okay, so I've been running CLMAF for a little bit and its worked pretty well, now I switched injectors, and have been working more in OLSD and its going well. but I tried switching the MAF back on to check it out. and it runs excessively lean. remember the only mechanical change was fuel injectors. I switched from the old LT1 style rochester fat body injectors to some bosch 890's that were flow tested and further tested by YAW power to get the offsets and what not.

okay, so the OLSD mode is looking fairly good, still need a little tweaking, but overall alot better than the older injectors, but re-enabling the MAF makes it run VERY lean (~1.35 EQ ratio)

I thought it may be a leak in the intake tubing after the MAF but before the throttle blade, letting in unmetered air, but before the throttle blade as to not affect the idle or running when not using the MAF, but I cannot find any leak, took the intake off between the MAF and TB, inspected all the sealing surfaces, and re-installed making sure everything is tight and I cannot hear, feel, or find any leaks.

I'm wondering if I'm missing something on the MAF re-enable?

attached is the OLMAF tune, as well as a short log of driving around a parking lot, and the OLSD tune I am currently using and a short log of driving around the neighborhood.

EDIT-vehicle is a '96 C1500 in the signature, using a 411 PCM based off an 02 X van tune

[mr.prick]

after re-enabling the MAF it maybe necessary to re-calibrate the MAF table.
after a lot of changes in OLSD i had found that after i re-enabled the MAF
i was extraordinarily lean and had to raise the MAF table by 20% just to get started.

[Aloicious]

after re-enabling the MAF it maybe necessary to re-calibrate the MAF table.
after a lot of changes in OLSD i had found that after i re-enabled the MAF
i was extraordinarily lean and had to raise the MAF table by 20% just to get started.

I thought the MAF table may have been way off too, I don't have a log of it, but I tried raising the entire MAF table 30%, thinking I would still be around 2-5% lean, and I could do some autoMAF tuning, but after raising it all up 30%, I was still running 35% lean.

I was also running the MAF with the old injectors and it worked fine, after swapping to the new injectors, there was only minimal changes done to the VE, desired airflow tables, injector voltage offsets, and small pulse adders. nothing radical though.

attached is one of the better CLMAF tunes I was using for a while prior to swapping injectors.

EDIT - later tonight if I have time, I may try raising the MAF table again since I've checked the intake tubing and made sure everything is tight since I tried raising it before. I'll try and get a log of that too.

[mr.prick]

FWIW
i had to play with IBPW after changing the IFR table.
(adjusted for increased FP, stock injectors)

and here`s some MAF links.
http://forum.efilive.com/showthread.php?t=6694&highlight=tune+maf
http://forum.efilive.com/showthread.php?t=1811&highlight=MAF+tuning
http://forum.efilive.com/showpost.php?p=49577&postcount=9
http://forum.efilive.com/showthread.php?t=6891&highlight=tune+maf
http://forum.efilive.com/showthread.php?t=6767&highlight=tune+maf
http://forum.efilive.com/showthread.php?t=6523&highlight=tune+maf

[Aloicious]

Well you were right Mr. Prick, the bottom end of the MAF calibration was out of whack, after about 125 miles of MAF tuning its getting in line fairly well. Thanks for the help

[joecar]

FWIW
i had to play with IBPW after changing the IFR table.
(adjusted for increased FP, stock injectors)

and here`s some MAF links.
http://forum.efilive.com/showthread.php?t=6694&highlight=tune+maf
http://forum.efilive.com/showthread.php?t=1811&highlight=MAF+tuning
http://forum.efilive.com/showpost.php?p=49577&postcount=9
http://forum.efilive.com/showthread.php?t=6891&highlight=tune+maf
http://forum.efilive.com/showthread.php?t=6767&highlight=tune+maf
http://forum.efilive.com/showthread.php?t=6523&highlight=tune+maf
In the last link I made some corrections to MAF/VE usage that I learned since the posts were made.

[Aloicious]

In the last link I made some corrections to MAF/VE usage that I learned since the posts were made.

I read your updates and have a theoretical question now.
you said:

If RPM is above B0120 (usually 4000 rpm), then PCM uses MAF;
If RPM is below B0120, PCM uses combination of VE and MAF (transient->VE, steady state->MAF);


so theoretically, if someone planned to use the MAF, why would they want to filter out the transient cells when tuning the VE? I know why it is done when planning on staying in OLSD mode exclusively. but if someone wants to use the MAF, and is doing an autoVE prior to enabling the MAF, wouldn't they want to keep the transient fueling (ie. throttle changes, etc.) calculated in the VE? that way when as you say, the throttle is steady, it calculates using MAF, and then the transient states using the VE calculations would be more correct.

if that makes any sense, or am I just looking at this bass ackwards?

[joecar]

During a tranisition the response is delayed by some amount...

compare these two situations:
- as throttle is opening it move thru positon X at some rpm R, MAP/airflow are catching up (they lag slightly);
- throttle is steady at the same position X at the same rpm R, MAP/airflow are steady at their true value;

(and assuming all other parameters are the same)

the airmass calculated from X, R, MAP will be different in each case;

Also, the transient case will have different values depending on the rate of transition.

You want the true steady conditions relfected in the VE/MAF tables so that when they are looked up they report the true values...

the transient conditions have to be handled by the "other" tables (PE, stomp/pumpshot, ...).

[Aloicious]

During a tranisition the response is delayed by some amount...

compare these two situations:
- as throttle is opening it move thru positon X at some rpm R, MAP/airflow are catching up (they lag slightly);
- throttle is steady at the same position X at the same rpm R, MAP/airflow are steady at their true value;

(and assuming all other parameters are the same)

the airmass calculated from X, R, MAP will be different in each case;

Also, the transient case will have different values depending on the rate of transition.

You want the true steady conditions relfected in the VE/MAF tables so that when they are looked up they report the true values...

the transient conditions have to be handled by the "other" tables (PE, stomp/pumpshot, ...).


Okay I get what you're saying. that makes sense. I forgot to think about the rate of transistion change affecting the tranisient values within the same area.