Does your SLP MAF "flatline"?
07-11-2004, 10:58 PM
#1
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Does your SLP MAF "flatline"? I finally switched over to a descreened truck MAF
and truck MAF table, which seems to be working
out OK (LTFTs are still accumulating, a bit more
negative than my SLP MAF setup w/ resistor tweak
and stock F-body table; but that is something I
will let soak, and adjust later).
In logging my old setup, I noticed that the SLP MAF
frequency basically "flatlined" about 10,000 Hz if you
looked at MAF Frequency vs RPM, or RPM*MAP, on
an Excel scatter plot. This bothered me. I do not
see the truck MAF doing this; its output continues
increasing all the way to upshift (as it should).
My MAF frequency now is not -that- much higher
(10500Hz, maybe) but it responds sensibly to the
continuum of engine airflow.
I will be sticking with the truck MAF from here on out
I expect, just have to tailor the low end of the MAF
table a bit it seems (the top end, higher-flow fuel
trim cells are happy campers). I also had reset my
FTC boundaries to get all of them "live" on this '02
F-body, which seems to have worked out OK.
I'm wondering whether there are any other SLP MAF
users out there who can confirm this behavior (the
MAF frequency sort of "pegging" at about 5500RPM
and up, more or less, probably varies by mods). I'm
kind of suspicious that the resistor "calibration" that
fixes up the low end by pulling frequency, might
cost the high end fidelity, even to the point of
"clipping" (can you say ugly fuel fade, psychosomatic?).
and truck MAF table, which seems to be working
out OK (LTFTs are still accumulating, a bit more
negative than my SLP MAF setup w/ resistor tweak
and stock F-body table; but that is something I
will let soak, and adjust later).
In logging my old setup, I noticed that the SLP MAF
frequency basically "flatlined" about 10,000 Hz if you
looked at MAF Frequency vs RPM, or RPM*MAP, on
an Excel scatter plot. This bothered me. I do not
see the truck MAF doing this; its output continues
increasing all the way to upshift (as it should).
My MAF frequency now is not -that- much higher
(10500Hz, maybe) but it responds sensibly to the
continuum of engine airflow.
I will be sticking with the truck MAF from here on out
I expect, just have to tailor the low end of the MAF
table a bit it seems (the top end, higher-flow fuel
trim cells are happy campers). I also had reset my
FTC boundaries to get all of them "live" on this '02
F-body, which seems to have worked out OK.
I'm wondering whether there are any other SLP MAF
users out there who can confirm this behavior (the
MAF frequency sort of "pegging" at about 5500RPM
and up, more or less, probably varies by mods). I'm
kind of suspicious that the resistor "calibration" that
fixes up the low end by pulling frequency, might
cost the high end fidelity, even to the point of
"clipping" (can you say ugly fuel fade, psychosomatic?).
07-12-2004, 12:06 AM
#2
We have hooked up several MAF's to an ocillascope to determine what the usable frequency is of the GM MAF. Unfortunately, ALL of them fail to continue to report frequency accuratly above 10k - 11k Hz.
We were doing this to help determine if cutting the MAF freq in half could be used for supercharger or turbo applications. Basically, it doesn't work because the MAF will not properly report much beyound that indicated in the MAF max freq on LS1 edit or HP Tuners........... again, I guess GM knew what they were doing.....
Good Luck
We were doing this to help determine if cutting the MAF freq in half could be used for supercharger or turbo applications. Basically, it doesn't work because the MAF will not properly report much beyound that indicated in the MAF max freq on LS1 edit or HP Tuners........... again, I guess GM knew what they were doing.....
Good Luck
07-12-2004, 09:00 AM
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Well, so far I haven't gotten an air (vacuum)
source that will peg my MAFs so I haven't been
able to go as far as determining the output
frequency limit. But even if the output were
inaccurate, as long as it still moves with
airflow it can still be calibrated up. Thing is,
the SLP doesn't move while airflow does;
the truck unit, at least follows RPM*MAP.
source that will peg my MAFs so I haven't been
able to go as far as determining the output
frequency limit. But even if the output were
inaccurate, as long as it still moves with
airflow it can still be calibrated up. Thing is,
the SLP doesn't move while airflow does;
the truck unit, at least follows RPM*MAP.