Screened vs Descreened 85mm MAF
04-15-2004, 09:16 AM
#1
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Screened vs Descreened 85mm MAF Having a tough time getting a hefty enough
extractor (blower) to fully exercise my MAFs
(ghetto flow bench). But I did some testing
on a pair of Delphi 85mm units I got off eBay
(separately). In this instance I used a blower
off a small outdoor A/C unit.
Both units screened, against this A/C blower,
read 6600Hz (approx 70 gm/sec mass airflow on
these truck MAFs). Good unit-unit matching.
I removed the screen from one unit and its freq
jumped to 6950Hz, or 80 gm/sec airflow.
The blower I am using is pretty quiet and you
can hear a lot of whistling in the screen even
at this small airflow (roughly 1/6 of full scale).
The screen is making micro-turbulence I
believe, which is only going to get worse
geometrically w/ flow (velocity).
I believe the airflow in the MAFs themselves is
pretty smooth and even as I used a PVC pipe
adapter to get them up away from the blower
inlet.
Next step up is a belt drive whole-house
blower and an integral-horsepower motor....
extractor (blower) to fully exercise my MAFs
(ghetto flow bench). But I did some testing
on a pair of Delphi 85mm units I got off eBay
(separately). In this instance I used a blower
off a small outdoor A/C unit.
Both units screened, against this A/C blower,
read 6600Hz (approx 70 gm/sec mass airflow on
these truck MAFs). Good unit-unit matching.
I removed the screen from one unit and its freq
jumped to 6950Hz, or 80 gm/sec airflow.
The blower I am using is pretty quiet and you
can hear a lot of whistling in the screen even
at this small airflow (roughly 1/6 of full scale).
The screen is making micro-turbulence I
believe, which is only going to get worse
geometrically w/ flow (velocity).
I believe the airflow in the MAFs themselves is
pretty smooth and even as I used a PVC pipe
adapter to get them up away from the blower
inlet.
Next step up is a belt drive whole-house
blower and an integral-horsepower motor....
04-15-2004, 06:38 PM
#2
Originally Posted by jimmyblue
Having a tough time getting a hefty enough
extractor (blower) to fully exercise my MAFs
(ghetto flow bench). But I did some testing
on a pair of Delphi 85mm units I got off eBay
(separately). In this instance I used a blower
off a small outdoor A/C unit.
Both units screened, against this A/C blower,
read 6600Hz (approx 70 gm/sec mass airflow on
these truck MAFs). Good unit-unit matching.
I removed the screen from one unit and its freq
jumped to 6950Hz, or 80 gm/sec airflow.
The blower I am using is pretty quiet and you
can hear a lot of whistling in the screen even
at this small airflow (roughly 1/6 of full scale).
The screen is making micro-turbulence I
believe, which is only going to get worse
geometrically w/ flow (velocity).
I believe the airflow in the MAFs themselves is
pretty smooth and even as I used a PVC pipe
adapter to get them up away from the blower
inlet.
Next step up is a belt drive whole-house
blower and an integral-horsepower motor....
extractor (blower) to fully exercise my MAFs
(ghetto flow bench). But I did some testing
on a pair of Delphi 85mm units I got off eBay
(separately). In this instance I used a blower
off a small outdoor A/C unit.
Both units screened, against this A/C blower,
read 6600Hz (approx 70 gm/sec mass airflow on
these truck MAFs). Good unit-unit matching.
I removed the screen from one unit and its freq
jumped to 6950Hz, or 80 gm/sec airflow.
The blower I am using is pretty quiet and you
can hear a lot of whistling in the screen even
at this small airflow (roughly 1/6 of full scale).
The screen is making micro-turbulence I
believe, which is only going to get worse
geometrically w/ flow (velocity).
I believe the airflow in the MAFs themselves is
pretty smooth and even as I used a PVC pipe
adapter to get them up away from the blower
inlet.
Next step up is a belt drive whole-house
blower and an integral-horsepower motor....
6000 6125 6250 6375 6500 6625 6750 6875 7000
51.66 54.98 58.44 62.05 65.82 69.73 73.8 78.03 82.41
Here is Descreened 2002 Z06-
6000 6125 6250 6375 6500 6625 6750 6875 7000
50.4 53.77 57.3 61.01 64.88 68.91 73.12 77.47 81.97
Backtracking from Gram/sec everything looks good. FWIW.
04-15-2004, 07:31 PM
#3
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From my observation the descreen did increase the
amount of air flowed a fair bit but I do not believe
the sensing was affected (in an unbiased laminar inlet
flow situation). I put an unconnected, screened 85mm
Delphi in front of the unscreened, and the unscreened
dropped its output to about 6300Hz (lower than the
screened Delphis individually).
amount of air flowed a fair bit but I do not believe
the sensing was affected (in an unbiased laminar inlet
flow situation). I put an unconnected, screened 85mm
Delphi in front of the unscreened, and the unscreened
dropped its output to about 6300Hz (lower than the
screened Delphis individually).
04-16-2004, 09:01 AM
#5
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Well, it's only working to a point... I need
MORE FLOW!!! That and the "golden unit"
calibration on one of my Delphi MAFs. But
it's sputtering in the garage (actually the
kitchen floor) anyway.
MORE FLOW!!! That and the "golden unit"
calibration on one of my Delphi MAFs. But
it's sputtering in the garage (actually the
kitchen floor) anyway.
04-17-2004, 12:52 AM
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04-17-2004, 07:57 AM
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Originally Posted by deezel
For an air flow source, have you considered these?
carpet dryer
carpet dryer
gone through & come up short. Just ordered a bunch of
sprockets & chain from surpluscenter.com to hook up my
biggest one to a 2HP motor. But I'm watching a carpet
blower on eBay now that's cheaper than the hardware....
04-17-2004, 08:14 PM
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From the looks of things the change to metering
(with a straight-line input tract) is minimal. On the
c5howto page they give a table with and w/o
screen and it looks like this indicates a small and
variable scaling of airflow. One of the things I
want this bench for, is to do things like tandem
testing a screened and descreened MAF with the
same air, and get a recalibration I believe in.
I think unless your intake tract has a hard bend
with a foot of the MAF, you could probably just
leave it be.
http://c5howto.com/index.php?article=25
from http://c5howto.com/index.php?article=25
Frequency Screened Descreened
1500 1.48 1.42
1625 1.8 1.76
1750 2.13 2.1
1875 2.49 2.48
2000 2.89 2.86
2125 3.33 3.26
2250 3.8 3.7
2375 4.34 4.18
2500 4.91 4.71
2625 5.54 5.31
2750 6.22 5.97
2875 6.95 6.68
3000 7.73 7.43
3125 8.56 8.23
3250 9.45 9.08
3375 10.38 9.97
3500 11.38 10.91
3625 12.45 11.93
3750 13.6 13.05
3875 14.85 14.27
4000 16.21 15.59
4125 17.7 16.98
4250 19.32 18.47
4375 21.02 20.05
4500 22.77 21.72
4625 24.54 23.48
4750 26.43 25.34
4875 28.41 27.28
5000 30.49 29.34
5125 32.66 31.48
5250 34.95 33.74
5375 37.36 36.11
5500 39.9 38.62
5625 42.62 41.3
5750 45.48 44.17
5875 48.5 47.2
6000 51.66 50.4
6125 54.98 53.77
6250 58.44 57.3
6375 62.05 61.01
6500 65.82 64.88
6625 69.73 68.91
6750 73.8 73.12
6875 78.03 77.47
7000 82.41 81.97
7125 86.94 86.63
7250 91.63 91.45
7375 96.49 96.43
7500 101.51 101.59
7625 106.71 106.9
7750 112.09 112.36
7875 117.63 118.01
8000 123.35 123.83
8125 129.24 129.84
8250 135.3 136.05
8375 141.53 142.48
8500 147.87 149.13
8625 154.41 155.98
8750 161.15 163.06
8875 168.08 170.38
9000 175.22 177.92
9125 182.58 185.7
9250 190.23 193.73
9375 198.21 201.99
9500 206.34 210.52
9625 214.8 219.3
9750 223.52 228.34
9875 232.52 237.64
10000 241.83 247.23
10125 251.34 257.06
10250 261.13 267.16
10375 271.19 277.56
10500 281.53 288.25
10625 292.15 299.25
10750 303.05 310.55
10875 314.25 322.2
11000 325.73 334.16
11125 337.51 346.49
11250 349.59 359.16
11375 361.96 372.22
11500 374.64 385.66
11625 387.63 399.51
11750 400.92 413.77
11875 414.53 428.45
12000 428.46 443.6
(with a straight-line input tract) is minimal. On the
c5howto page they give a table with and w/o
screen and it looks like this indicates a small and
variable scaling of airflow. One of the things I
want this bench for, is to do things like tandem
testing a screened and descreened MAF with the
same air, and get a recalibration I believe in.
I think unless your intake tract has a hard bend
with a foot of the MAF, you could probably just
leave it be.
http://c5howto.com/index.php?article=25
from http://c5howto.com/index.php?article=25
Frequency Screened Descreened
1500 1.48 1.42
1625 1.8 1.76
1750 2.13 2.1
1875 2.49 2.48
2000 2.89 2.86
2125 3.33 3.26
2250 3.8 3.7
2375 4.34 4.18
2500 4.91 4.71
2625 5.54 5.31
2750 6.22 5.97
2875 6.95 6.68
3000 7.73 7.43
3125 8.56 8.23
3250 9.45 9.08
3375 10.38 9.97
3500 11.38 10.91
3625 12.45 11.93
3750 13.6 13.05
3875 14.85 14.27
4000 16.21 15.59
4125 17.7 16.98
4250 19.32 18.47
4375 21.02 20.05
4500 22.77 21.72
4625 24.54 23.48
4750 26.43 25.34
4875 28.41 27.28
5000 30.49 29.34
5125 32.66 31.48
5250 34.95 33.74
5375 37.36 36.11
5500 39.9 38.62
5625 42.62 41.3
5750 45.48 44.17
5875 48.5 47.2
6000 51.66 50.4
6125 54.98 53.77
6250 58.44 57.3
6375 62.05 61.01
6500 65.82 64.88
6625 69.73 68.91
6750 73.8 73.12
6875 78.03 77.47
7000 82.41 81.97
7125 86.94 86.63
7250 91.63 91.45
7375 96.49 96.43
7500 101.51 101.59
7625 106.71 106.9
7750 112.09 112.36
7875 117.63 118.01
8000 123.35 123.83
8125 129.24 129.84
8250 135.3 136.05
8375 141.53 142.48
8500 147.87 149.13
8625 154.41 155.98
8750 161.15 163.06
8875 168.08 170.38
9000 175.22 177.92
9125 182.58 185.7
9250 190.23 193.73
9375 198.21 201.99
9500 206.34 210.52
9625 214.8 219.3
9750 223.52 228.34
9875 232.52 237.64
10000 241.83 247.23
10125 251.34 257.06
10250 261.13 267.16
10375 271.19 277.56
10500 281.53 288.25
10625 292.15 299.25
10750 303.05 310.55
10875 314.25 322.2
11000 325.73 334.16
11125 337.51 346.49
11250 349.59 359.16
11375 361.96 372.22
11500 374.64 385.66
11625 387.63 399.51
11750 400.92 413.77
11875 414.53 428.45
12000 428.46 443.6
