Does MAF control PE AFR?
05-26-2005, 11:12 AM
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Does MAF control PE AFR? I finished tuning the VE table via wideband. All LTFT are +1to -4.
Tuned MAF afterwards. The one I tuned was bigger than the monaro.
When the car goes into PE mode, actual AFR runs about 13.5 when commanded AFR is 12.6
Could this be caused by a bad MAF freq table? What is a good stock MAF table to use?
Notes: COT/DFCO off, lid, descreened TB.
Tuned MAF afterwards. The one I tuned was bigger than the monaro.
When the car goes into PE mode, actual AFR runs about 13.5 when commanded AFR is 12.6
Could this be caused by a bad MAF freq table? What is a good stock MAF table to use?
Notes: COT/DFCO off, lid, descreened TB.
05-26-2005, 11:59 AM
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Airflow uses MAF data entirely, above 4KRPM, as long
as MAP is stable (and no faults / tricks).
Need to know what MAF you have. Bigger (pysically)
is either one of the stock Delphi, a modified Delphi
(SLP, Pace) or a Granatelli unit.
For stock Delphi I favor the table from the '02 6.0
trucks. I have one line in my spreadsheet that says
it's from a Z71 6.0 that nicely populates the low end
(where most others stop short or have hokey
discontinuities). Had some dude tell me that there's
no such thing as a 6-liter Z71, but that's the label
that was on it when I got it.
For the modified Delphi, I say unmodify it (desolder
the resistor you'll find attached to two of the legs,
looking from the back down the throat) and use the
truck table. The early SLP and the Pace are "calibrated"
a bit on the lean side as a voodoo way of getting a
"proper" PE result against a stock (fat) table; shave
off a point or so of AFR. Pull the sticker off a SLP MAF
and underneath is a Delphi tag and ground-off serial
number. Slick and professional, yessir.
The GMAF, that's an entirely 'nother critter. I think
there are some folks on the 'boards who've gone and
tuned in their GMAF with a better table by now; I have
yet to get my hands on those tables though.
Here's the truck table I like:
MAF Type freq Hz 750 800 850 900 950 1000 1050 1100 1150 1200 1250 1300 1350 1400 1450 1500 1625 1750 1875 2000 2125 2250 2375 2500 2625 2750 2875 3000 3125 3250 3375 3500 3625 3750 3875 4000 4125 4250 4375 4500 4625 4750 4875 5000 5125 5250 5375 5500 5625 5750 5875 6000 6125 6250 6375 6500 6625 6750 6875 7000 7125 7250 7375 7500 7625 7750 7875 8000 8125 8250 8375 8500 8625 8750 8875 9000 9125 9250 9375 9500 9625 9750 9875 10000 10125 10250 10375 10500 10625 10750 10875 11000 11125 11250 11375 11500 11625 11750 11875 12000
Truck ZL1 02 flow gm/s 0.2 0.27 0.34 0.41 0.49 0.58 0.66 0.73 0.81 0.89 0.97 1.05 1.13 1.21 1.29 1.59 1.88 2.2 2.58 2.99 3.45 3.95 4.5 5.1 5.76 6.46 7.23 8.06 8.95 9.9 10.91 11.98 13.14 14.39 15.74 17.19 18.74 20.39 22.14 23.99 25.95 27.99 30.14 32.38 34.71 37.16 39.73 42.5 45.41 48.47 51.67 55.02 58.48 62.1 65.86 69.77 73.82 78.06 82.48 87.07 91.82 96.74 101.82 107.08 112.48 118.07 123.83 129.76 135.87 142.17 148.61 155.26 162.11 169.17 176.44 183.94 191.72 199.8 208.06 216.62 225.44 234.52 243.89 253.45 263.21 273.23 283.55 294.15 305.06 316.32 327.93 339.92 352.32 365.16 378.47 392.3 406.7 421.7 437.34 453.69
If you use this table against a resistor "calibrated" unit
you will get some very lean results; conversely if you run
a stock truck MAF on an stock tune F-body it will be piggy
rich. Inspect the hardware and see what the real deal is.
Here's what to look for, regarding the "calibrated" units'
resistor:
as MAP is stable (and no faults / tricks).
Need to know what MAF you have. Bigger (pysically)
is either one of the stock Delphi, a modified Delphi
(SLP, Pace) or a Granatelli unit.
For stock Delphi I favor the table from the '02 6.0
trucks. I have one line in my spreadsheet that says
it's from a Z71 6.0 that nicely populates the low end
(where most others stop short or have hokey
discontinuities). Had some dude tell me that there's
no such thing as a 6-liter Z71, but that's the label
that was on it when I got it.
For the modified Delphi, I say unmodify it (desolder
the resistor you'll find attached to two of the legs,
looking from the back down the throat) and use the
truck table. The early SLP and the Pace are "calibrated"
a bit on the lean side as a voodoo way of getting a
"proper" PE result against a stock (fat) table; shave
off a point or so of AFR. Pull the sticker off a SLP MAF
and underneath is a Delphi tag and ground-off serial
number. Slick and professional, yessir.
The GMAF, that's an entirely 'nother critter. I think
there are some folks on the 'boards who've gone and
tuned in their GMAF with a better table by now; I have
yet to get my hands on those tables though.
Here's the truck table I like:
MAF Type freq Hz 750 800 850 900 950 1000 1050 1100 1150 1200 1250 1300 1350 1400 1450 1500 1625 1750 1875 2000 2125 2250 2375 2500 2625 2750 2875 3000 3125 3250 3375 3500 3625 3750 3875 4000 4125 4250 4375 4500 4625 4750 4875 5000 5125 5250 5375 5500 5625 5750 5875 6000 6125 6250 6375 6500 6625 6750 6875 7000 7125 7250 7375 7500 7625 7750 7875 8000 8125 8250 8375 8500 8625 8750 8875 9000 9125 9250 9375 9500 9625 9750 9875 10000 10125 10250 10375 10500 10625 10750 10875 11000 11125 11250 11375 11500 11625 11750 11875 12000
Truck ZL1 02 flow gm/s 0.2 0.27 0.34 0.41 0.49 0.58 0.66 0.73 0.81 0.89 0.97 1.05 1.13 1.21 1.29 1.59 1.88 2.2 2.58 2.99 3.45 3.95 4.5 5.1 5.76 6.46 7.23 8.06 8.95 9.9 10.91 11.98 13.14 14.39 15.74 17.19 18.74 20.39 22.14 23.99 25.95 27.99 30.14 32.38 34.71 37.16 39.73 42.5 45.41 48.47 51.67 55.02 58.48 62.1 65.86 69.77 73.82 78.06 82.48 87.07 91.82 96.74 101.82 107.08 112.48 118.07 123.83 129.76 135.87 142.17 148.61 155.26 162.11 169.17 176.44 183.94 191.72 199.8 208.06 216.62 225.44 234.52 243.89 253.45 263.21 273.23 283.55 294.15 305.06 316.32 327.93 339.92 352.32 365.16 378.47 392.3 406.7 421.7 437.34 453.69
If you use this table against a resistor "calibrated" unit
you will get some very lean results; conversely if you run
a stock truck MAF on an stock tune F-body it will be piggy
rich. Inspect the hardware and see what the real deal is.
Here's what to look for, regarding the "calibrated" units'
resistor:
05-26-2005, 01:15 PM
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Stock ACdelco MAF minus screen.
Correct me if I'm mistaken:
A lean AFR in PE mode indicates that the MAF is returning a lower airflow value than actual. Right?
So, the MAF table being used is too small and under reports gm/s at each maf freq.
What concerns me is that this table is bigger than any OEM calibration. Please tell me if the above is correct and I need to increase g/s v freq. Thanks.
Correct me if I'm mistaken:
A lean AFR in PE mode indicates that the MAF is returning a lower airflow value than actual. Right?
So, the MAF table being used is too small and under reports gm/s at each maf freq.
What concerns me is that this table is bigger than any OEM calibration. Please tell me if the above is correct and I need to increase g/s v freq. Thanks.
05-26-2005, 01:41 PM
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Originally Posted by SSpeedracer
Stock ACdelco MAF minus screen.
Correct me if I'm mistaken:
A lean AFR in PE mode indicates that the MAF is returning a lower airflow value than actual. Right?
So, the MAF table being used is too small and under reports gm/s at each maf freq.
What concerns me is that this table is bigger than any OEM calibration. Please tell me if the above is correct and I need to increase g/s v freq. Thanks.
Correct me if I'm mistaken:
A lean AFR in PE mode indicates that the MAF is returning a lower airflow value than actual. Right?
So, the MAF table being used is too small and under reports gm/s at each maf freq.
What concerns me is that this table is bigger than any OEM calibration. Please tell me if the above is correct and I need to increase g/s v freq. Thanks.
Just some interesting #s though, your MAF may be flowing anywhere b/w 20-40% more if descreened and ported.
05-26-2005, 09:32 PM
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JB- thanks for the background.
TX- thanks for the 1% to .1AFR conversion. Worked like a champ.
I am blown away how much descreening the MAF has altered the calibration. I'm going to recalibrate to fine tune via SD and Red's spreadsheet. Right now its running about .1 richer than commanded. The calibration curve is steeper than anything I've seen factory from GM/Holden. Wonder if sealing up the FTRA has anything to do with it. Too bad it doesnt take speed into the equation LOL.
TX- thanks for the 1% to .1AFR conversion. Worked like a champ.
I am blown away how much descreening the MAF has altered the calibration. I'm going to recalibrate to fine tune via SD and Red's spreadsheet. Right now its running about .1 richer than commanded. The calibration curve is steeper than anything I've seen factory from GM/Holden. Wonder if sealing up the FTRA has anything to do with it. Too bad it doesnt take speed into the equation LOL.
