View Full Version : VE table great, MAF hooked up, car slower??


silverTA2002
04-15-2006, 12:39 PM
Where the heck did my torque go???

I've gotten my VE table pretty much dead on (all LTFTs from -4 to 0).

I logged Maf Hz vs. Dynamic airflow on two days for an hour and a half. Changed my MAF table. Set everything back to normal (MAF fail freq 13500, low octane spark back to high octane minus 4, etc.).

Then I just drove around for about 10 minutes, down low, all that TQ that I feel I've gained from SD tuning is GONE.

From my VE table tuning, I feel like I've gained TONS of tq from 2000 to 4000 rpm. But, with the MAF back in, it feels like all the gains are gone. :confused:

I'm thinking about just leaving the MAF off. Any thoughts?

silverTA2002
04-15-2006, 12:41 PM
Do my fuel trims need to relearn after a flash? From that short log, they're all still a little negative (except below 2k, but that's not where I'm feeling the power loss)

LTFT from short log right after reflash.

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 -3 -3 -1 0 0 0 0 0 0 0 0 0 1 0
0 0 -4 -2 -4 -2 0 0 0 0 0 0 0 0 1 0 0
0 -4 -4 -3 -3 -3 0 0 0 0 0 0 0 0 0 0 0
0 -6 -5 -6 -6 -5 -1 -1 -1 0 0 0 0 0 0 0 0
0 -4 -7 -7 -7 -1 -1 -1 0 0 0 0 0 0 0 0 0
0 -6 -5 -7 -6 -3 -1 -1 -2 0 -1 0 0 0 0 0 0
-6 -7 -7 -7 -6 -2 -1 -1 -1 0 0 0 0 0 0 0 0
-6 -7 -6 -5 -2 -6 -1 -1 0 0 0 0 0 0 0 0 2
0 -3 -3 -2 -3 -3 -1 0 -2 0 0 0 0 0 0 0 0
0 -4 -4 -1 -2 -2 -2 0 0 -3 0 0 0 0 0 0 0
0 -2 -2 -4 -3 -2 -2 -3 -2 0 0 0 0 0 0 0 0
0 0 -1 -5 -2 -2 -2 -2 -2 -1 0 0 0 0 0 0 0
0 0 0 -2 -1 0 -2 -2 -2 -1 0 0 0 0 0 0 0
0 0 0 -1 -2 -3 -2 -2 -1 -1 0 0 0 0 0 0 0
0 0 0 -1 -3 -2 -2 -1 -1 0 0 0 0 0 0 0 0
0 0 -3 -2 -2 -3 -2 -1 0 0 0 0 0 0 0 0 0
0 0 -3 0 -1 -1 -1 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

99whitews6
04-15-2006, 12:46 PM
Well, I usually get my numbers a little closer to zero than -7. Beyond that, I too felt a noticable difference going from SD to MAF which is why the MAF is no longer part of my intake! :)

Ditch the MAF if you are comfortable with VE tuning every once and a while :drive:

silverTA2002
04-15-2006, 12:50 PM
Well, I usually get my numbers a little closer to zero than -7. Beyond that, I too felt a noticable difference going from SD to MAF which is why the MAF is no longer part of my intake! :)

Ditch the MAF if you are comfortable with VE tuning every once and a while :drive:

So, how do you "delete" the MAF in the computer with HP tuners?

Set MAF fail frequency to zero and disable P101,102 and 103?

What about the high octane and low octane spark tables?

I know how to disable it temporarily for tuning, I'm just not sure how to delete it semi permanently.

I'll probably leave it hooked up to the car, I just don't think I'm going to want to use it for right now.

Anything that makes the car feel slower has to go. :)

silverTA2002
04-15-2006, 01:17 PM
Also, I just looked at my log again. My timing seems a bit low across the board.

It looks like I'm in the low octane table.

Why would I be there if I just reflashed and enabled my MAF. I don't have an SES light. Does the computer remember when the MAF was just set to fail at 0?

How do I get back into the high octane table?

Ideally, I'd like for my MAF to work. Maybe I'm jumping the gun.

silverTA2002
04-15-2006, 06:21 PM
I did another log. Seems like I spoke too soon. Now, I'm apparently back in the high octane table, and my power feels back from 2k-4k rpms.

But, my MAF is off a bit in the lower rpms.

Here are my LTFT from this log.



-1.71875 -1.82291 -1.43229 -1.80747 -1.97233 -2.70041 -2.83203 -3.00071 -3.03485 -2.03536 -0.89844 1.56250
-1.17187 -2.64625 -3.21422 -2.33466 -1.91216 -2.25089 -2.50651 -2.34375 -1.75781 0.00000 0.13021
-3.29478 -3.32214 -3.10132 -2.49310 -2.32515 -2.20853 -2.34375 -0.78125 -3.90625 0.00000
-3.59976 -3.68834 -4.35988 -3.74264 -5.15434 -2.67578 -2.86458 -2.89062 -2.84598 0.00000 -1.69271 -3.90625 1.56250
-7.02673 -5.10133 -6.00666 -6.00461 -4.96238 -3.30255 -2.62784 -3.12500 -2.14844 -3.51562 -0.39062 0.00000 0.00000
-5.99347 -6.51999 -6.76731 -5.34474 -6.88733 -3.63898 -3.80859 -2.83203 -2.34375 -3.90625 0.00000
-8.98437 -5.53314 -7.50434 -7.26396 -5.35590 -5.64453 -3.57572 -3.38542 -2.92969 -2.34375
-7.94271 -6.18379 -7.48332 -6.72907 -7.42187 -5.68182 -3.80859 -2.60416 -1.17187 -2.05078 0.00000 0.00000 1.56250
-8.20312 -7.09918 -6.19237 -6.09976 -4.92996 -4.49219 -4.02344 -3.28125 -2.34375 -1.56250 0.00000 0.00000 0.00000
-6.11979 -4.01278 -4.81771 -3.53906 -3.79464 -5.37860 -2.44140 -2.27864 -1.88802 -1.95312 -3.12500 -1.56250 0.00000
-2.79948 -3.96701 -3.24929 -2.56510 -3.08594 -3.51562 -1.04166 -1.60590 -1.56250 0.00000 0.00000
-3.51562 -4.44336 -4.14402 -4.14663 -4.23177 -3.67187 -1.61458 -1.75781 -4.88281 0.00000 0.00000 0.00000
-3.40909 -4.66890 -4.50994 -4.52009 -1.82291 -2.80540 -2.05078 -2.34375 0.00000 0.00000 0.00000
-2.73437 -3.22265 -3.45982 -2.21354 -2.99479 -2.37380 -2.86458 -3.41797 0.00000 0.00000 0.00000
-3.18080 -3.23989 -2.90798 -2.69531 -3.03199 -2.91193 -1.81108 -2.69531 0.00000 0.00000 0.00000 0.00000
-2.73437 -2.56454 -3.00377 -2.62920 -3.00611 -2.51562 -2.69396 -1.69271 0.00000 0.00000 0.00000 0.00000 0.52084 1.56250
-3.12500 -2.59046 -2.39955 -2.61230 -3.37027 -3.68089 -2.51562 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000
-2.63672 -1.36719 -1.18850 -0.98407 -0.86263 -0.45363 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000

I also downloaded HPT ver 2.1. It has WAY more you can do with histograms. I setup one to monitor MAF frequency (Hz) and Commanded A/F High res (not sure what this does.....) according to http://www.hptuners.com/forum/showthread.php?t=5369

I got these results in the histogram..... for 2375 to 8250

-5.89844 -7.01506 -5.86689 -3.81798 -3.18926 -3.81016 -4.04358 -3.90934 -3.72858 -3.54134 -3.46147 -2.93322 -4.48157 -5.65924 -5.24060 -4.63125 -4.93809 -4.68750 -4.34743 -5.00422 -4.83333 -3.93827 -4.42954 -3.85653 -3.36602 -3.90625 -4.98798 -4.02462 -3.05325 -3.41082 -3.66951 -2.94859 -3.44172 -2.96303 -2.69804 -3.11651 -2.83854 -2.59548 -3.29241 -2.90178 -3.42262 -3.16162 -2.87109 -3.63281 -3.97135 -2.85644 -2.41477 -2.14844

What do I do with these figures? The thread says to copy/paste and special multiply into my MAF table. But, I think that'll target me towards zero LTFT. I want to be about -2 to -4 like I setup my VE table. How do I do this?

Also, how do I know which LTFT cell corresponds to what MAF frequency?

silverTA2002
04-15-2006, 06:59 PM
Basically, I know what my LTFTs "should be" if the MAF is dead on to my SD tuning, how do I lean out the cells in my MAF that are too negative for LTFT (-7) back up to -3 or so?

Also, does increasing numbers in my MAF table make the car more rich or more lean?

silverTA2002
04-15-2006, 07:02 PM
Oh yeah, and while I'm asking questions......

Does the MAF have to be disabled to recalibrate it? I.E. Can you log MAF hz vs. Dynamic airflow with the MAF enabled?

silverTA2002
04-15-2006, 10:35 PM
Well, I think I found the answer to one of my questions.

Decrease the MAF table leans the car out, increase the MAF table adds fuel and richens.

But, after looking at logs, and excel spreadsheets of those logs. I'm still confused a bit about how to recalibrate the MAF.

The VE table values (that affect LTFTs) are measured by MAP vs. RPM.

The MAF table is measured by Frequency in Hz.

I can't figure out how MAP and RPM correspond to a MAF frequency. I sorted all the values in excel by MAP, then by RPM, and the MAF frequency is all over the place.

I want to be able to lean out specific cells that are too rich (kinda like how I tuned the VE table), but I don't know how to.

I did 2 hours of logging MAF freqency vs. Dynamic airflow, but it seems like the MAF is still making the car too rich under 2,500 rpm. And my butt o meter tells me I've lost power in that range with the MAF plugged in.

Basically, I need to lean it out by 3-4% from 40-75 MAP and 800-2400 rpm...... HOW?

jub jub
04-15-2006, 10:48 PM
LTFT's change from day to day depending on temp and barometric pressure. It sucks for tuning, but that's the reason the engineers put O2 sensors in line.

I can have a great VE table one day and the next it's all out of whack.

I just make sure that my car is always running a little in the neg so when I go WOT the LTFT's set at zero.

ZL1Killa
04-16-2006, 12:41 AM
decrease your MAF numbers or increase them according to your scan on that day.....

they will be off up to 5% either way depending on where you live maybe even more...
i live in Wilson, NC 40min east of Raleigh and I have my LTFTs around -2 and +3

and the car feels great....also it did take a little time to get it that way

muncie21
04-16-2006, 09:37 AM
wow, lots of questions. To answer one of them, the correlation between MAF (hz) and VE is the both are used to determine airflow, one is a look-up table (VE) and the other is a measurement instrument (MAF). In your scanner PID just log both values (in g/sec), the difference between the values is your error. Now you have to figure out which one you believe.

silverTA2002
04-16-2006, 11:37 AM
LTFT's change from day to day depending on temp and barometric pressure. It sucks for tuning, but that's the reason the engineers put O2 sensors in line.

I can have a great VE table one day and the next it's all out of whack.

I just make sure that my car is always running a little in the neg so when I go WOT the LTFT's set at zero.

The logs were all done on the same day, in the same conditions. So I don't think it's that.

silverTA2002
04-16-2006, 11:47 AM
wow, lots of questions. To answer one of them, the correlation between MAF (hz) and VE is the both are used to determine airflow, one is a look-up table (VE) and the other is a measurement instrument (MAF). In your scanner PID just log both values (in g/sec), the difference between the values is your error. Now you have to figure out which one you believe.

Are you talking about dynamic airflow vs. MAF airflow?

Do I have to log these in SD, or can I log with the MAF hooked up?

muncie21
04-16-2006, 12:06 PM
Yea, that's it. You can log it SD, but you have to have the MAF physically connected...meaning you can disable it by setting the MAF Hz fail to 0, but it needs to be connected to get a reading. I think the default unit of measure is lb/hr, but you should change that to g/sec for better resolution.

There's a MAF spreadsheet in the stickies that will spit out calculated flow rates for the MAF to help calibrate it.

silverTA2002
04-16-2006, 12:53 PM
Yea, that's it. You can log it SD, but you have to have the MAF physically connected...meaning you can disable it by setting the MAF Hz fail to 0, but it needs to be connected to get a reading. I think the default unit of measure is lb/hr, but you should change that to g/sec for better resolution.

There's a MAF spreadsheet in the stickies that will spit out calculated flow rates for the MAF to help calibrate it.

Ok, but do I HAVE to be in SD?

It seems like I'd be going backwards after having the MAF hooked up and running.

Shouldn't there be a way to calibrate the MAF by looking at LTFTs and adjusting from those with it hooked up?

I've already used the MAF spreadsheet with two hours of SD logs to get my FIRST MAF table recalibration.


Also, can I adjust my VE table with the MAF hooked up to "fix" my LTFTs, or do I have to adjust the MAF table?

I have specific CELLS that are too negative LTFTs right now. (-5 to -7) they are from 800 to 2400 rpm, and 35 to 60 MAP.

Of course they were about -2 to -3 with the MAF unhooked though. The PROBLEM is that the MAF frequency doesn't correspond to MAP and RPM like the VE table does.

BUT, somehow the MAF is messing with my trims in specific cells each time I log, but the frequency somehow doesn't actually correspond to those cells...... :confused:

In other words, if MAF frequency has nothing to do with MAP and RPM, then WHY does it keep making the car too rich in specific MAP and RPM cells?

If my MAF was off at, for example, 3000 hz, wouldn't ALL of my LTFTs be OFF at that frequency, since my VE table is good?


People are WAY right. Calibrating the MAF is much harder than just the VE table.

muncie21
04-16-2006, 01:50 PM
Here are the basics (as I understand them :) )
In closed loop--
* Below 4000RPM fueling is a combination of MAF and VE
* Above 4000RPM it's all MAF
* That's why you disconnect the MAF when you are updating your VE, so it doesn't interfere with the readings.
* When you think the VE is pretty good, compare the calculated dynamic airflows (derived from your VE table) with those of from your MAF. Since you've already tuned the VE, and errors should be errors in the MAF table. Which means you only need to update the MAF table now.
* Use the spreadsheet to determine new MAF value. Now the calculated airflows should pretty much match the MAF ones.

If your fuel trims are still off, then you could be having fueling (injector scaling) issues, but that's a whole new ball of wax