Screwdriver tuning the SLP85mm MAF
10-18-2003, 01:35 PM
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Screwdriver tuning the SLP85mm MAF http://community.webshots.com/album/95429402bLraTX
I removed the resistor (2.7Kohm code, measured 2.667K)
and ran wire pigtails through the wall so I could add
external circuitry instead. Right now it's only a pair
of resistors & a trimpot that I've adjusted to 2.6K in
order to richen things up a little. I expect to make
some refinements in packaging (waterproof would be nice)
and am hoping to get to a flat-LTFT operation (right now
it makes high negatives at low throttle, zeros to slight
positive higher up). I have to figure out some kind of
capacitive power-stealer for that. Meanwhile, I'm gonna
get my LTFTs down with a screwdriver.
Yeah, yeah, I could just use the MAFT, but....
The same thing could be done to the Z06 or regular Delphi
truck MAFs, add yer own resistor to adjust.
I removed the resistor (2.7Kohm code, measured 2.667K)
and ran wire pigtails through the wall so I could add
external circuitry instead. Right now it's only a pair
of resistors & a trimpot that I've adjusted to 2.6K in
order to richen things up a little. I expect to make
some refinements in packaging (waterproof would be nice)
and am hoping to get to a flat-LTFT operation (right now
it makes high negatives at low throttle, zeros to slight
positive higher up). I have to figure out some kind of
capacitive power-stealer for that. Meanwhile, I'm gonna
get my LTFTs down with a screwdriver.
Yeah, yeah, I could just use the MAFT, but....
The same thing could be done to the Z06 or regular Delphi
truck MAFs, add yer own resistor to adjust.
10-20-2003, 09:17 AM
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Re: Screwdriver tuning the SLP85mm MAF Revised the external resistor scheme to be DIP
switches & fixed resistors inside a plastic
semi-watertight plastic box.
Knocked the resistor value down to 2Kohms (approx)
and it sent my LTFTs way positive (+7 - +11).
I think it may have even put me to the low octane
table because when I filled up last night, all of
my LTFTs got reset to zero again. I thought only
spark was affected but, there it is.
Gonna try it with the resistor open and see if
that pushes the LTFTs negative instead.
switches & fixed resistors inside a plastic
semi-watertight plastic box.
Knocked the resistor value down to 2Kohms (approx)
and it sent my LTFTs way positive (+7 - +11).
I think it may have even put me to the low octane
table because when I filled up last night, all of
my LTFTs got reset to zero again. I thought only
spark was affected but, there it is.
Gonna try it with the resistor open and see if
that pushes the LTFTs negative instead.
10-20-2003, 01:34 PM
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Re: Screwdriver tuning the SLP85mm MAF Open resistor = pig rich and a too-rich DTC, -25% STFTs immediately, and LTFTs in the negative teens...
Interestingly, LTFTs update very fast when STFTs are grossly off.
1.8Kohm resistor = way lean
2.7Kohm (SLP value)= slightly lean (after rat-
tail file), fairly correct (before descreen &
filing down casting burrs)
Narrowing it down...
Interestingly, LTFTs update very fast when STFTs are grossly off.
1.8Kohm resistor = way lean
2.7Kohm (SLP value)= slightly lean (after rat-
tail file), fairly correct (before descreen &
filing down casting burrs)
Narrowing it down...
10-20-2003, 03:58 PM
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Re: Screwdriver tuning the SLP85mm MAF Good info. I take it you don't have edit? http://www.c5howto.com/index.php?article=25
10-20-2003, 04:12 PM
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Re: Screwdriver tuning the SLP85mm MAF No, haven't taken that plunge (& soaking) yet.
I'm just working off Predator real-time diag
although I've just bought EFILive (still have
to install to laptop & learn how to use).
I figure another couple days of "binary searching"
through resistor values will give me a map of how
much MAF resistor shunt makes how much % richer
or leaner (though I'll likely stop when it's good
for my setup).
The fact that no-resistor makes pig rich is
interesting, I thought this might be like the
LS-6 MAF that's supposed to be real lean out of
the box, but apparently this SLP-badged truck
MAF is a different critter. SLP ground off the
part number before sticking their badge on, so
I can't see what it really is, but I think this
unit (from GM parts) and a few minutes of cobbling
would make this a good general purpose F-body unit
on the cheap. Especially once I find the magic
resistor value for descreened and deburred.
I'm just working off Predator real-time diag
although I've just bought EFILive (still have
to install to laptop & learn how to use).
I figure another couple days of "binary searching"
through resistor values will give me a map of how
much MAF resistor shunt makes how much % richer
or leaner (though I'll likely stop when it's good
for my setup).
The fact that no-resistor makes pig rich is
interesting, I thought this might be like the
LS-6 MAF that's supposed to be real lean out of
the box, but apparently this SLP-badged truck
MAF is a different critter. SLP ground off the
part number before sticking their badge on, so
I can't see what it really is, but I think this
unit (from GM parts) and a few minutes of cobbling
would make this a good general purpose F-body unit
on the cheap. Especially once I find the magic
resistor value for descreened and deburred.
10-20-2003, 06:11 PM
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Re: Screwdriver tuning the SLP85mm MAF I believe I read somewhere it's just a standard truck MAF with the resistor added to try and "adjust" it for F-Body use. I've read where many removed the resistor and changed the tables in Edit with very good success. That is why I was asking. I have yet to "de resistor" mine and change the tables however.
10-24-2003, 10:34 PM
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Just an update...
Ran around with 3Kohms for a while, this
pushed on the LTFTs by about -5 to -6%
(relative to the 2.7Kohm original). Still a
bit of ping on opening throttle and WOT.
Swapped for 3.3Kohm yesterday. Car feels
very strong today, idle LTFTs are back to
about -10%, midband LTFTs are single
digit negative. Some of the less-used are
still updating. Seems to be negative across
the board and no pinging tonight. This has
the Predator power tune in with no spark
or PE adjustments yet.
Basically the descreen & debur of the SLP
MAF put a +8% or so adder on my LTFTs
and going from 2700 ohms to 3300 ohms
brought it back to original or maybe even
better.
Resistor Relative
Value "MAF Points"
2700 0
3000 -5
3300 -8
open -20 - -25, SES too rich
Because this is a parallel resistor combo
with the MAF wire the effect of increasing
resistor value is sublinear. Plenty of range
for F-bodies here though. I asked in the
truck forum about their MAF P/N, since
SLP ground mine off, will see if I can track
down the bargain core.
I may not dick with it for a while but this
may give some of you a starting "windage"
for your own MAF tweaking.
Ran around with 3Kohms for a while, this
pushed on the LTFTs by about -5 to -6%
(relative to the 2.7Kohm original). Still a
bit of ping on opening throttle and WOT.
Swapped for 3.3Kohm yesterday. Car feels
very strong today, idle LTFTs are back to
about -10%, midband LTFTs are single
digit negative. Some of the less-used are
still updating. Seems to be negative across
the board and no pinging tonight. This has
the Predator power tune in with no spark
or PE adjustments yet.
Basically the descreen & debur of the SLP
MAF put a +8% or so adder on my LTFTs
and going from 2700 ohms to 3300 ohms
brought it back to original or maybe even
better.
Resistor Relative
Value "MAF Points"
2700 0
3000 -5
3300 -8
open -20 - -25, SES too rich
Because this is a parallel resistor combo
with the MAF wire the effect of increasing
resistor value is sublinear. Plenty of range
for F-bodies here though. I asked in the
truck forum about their MAF P/N, since
SLP ground mine off, will see if I can track
down the bargain core.
I may not dick with it for a while but this
may give some of you a starting "windage"
for your own MAF tweaking.
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10-25-2003, 01:30 AM
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this is great new to me. I have been trying to tune the maf via ls1 edit and i go over the max range of programming. I ported my maf to the max(85mm) and descreaned it. LTFT went to +25. I was able to get the program to correct it down to +5 but no lower due to maxed out maf table. So i will give this a try and see if i can final tune with edit. Was also wondering if instead of hooking up resistors to dip switches, you could hook up an adjustable resistor (pot) sp?? and just change the value with a screwdriver. Cant see why that wouldnt work either...
10-25-2003, 09:28 AM
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You could (I have) use a pot although I don't consider
them very reliable especially in high-vibe environments.
The DIP switch you can see what you get, the pot you
have to measure. In the end I've found it easiest to just
pull the MAF and solder a new fixed resistor in the little
case (most of the time is in MAF relearning, not adjusting).
Stock (F-body) MAF might want a different value. The
85mm truck MAF sense resistors are 157 ohms cold,
maybe 300 hot? That would make some sense for the
3K resistors to be making 10%-type changes. If your
F-body MAF has a higher or lower value you might start
with a different value. Also have to determine whether the
MAF resistor bridge is the same config or not, F-bofy vs
truck, so as to shunt the right one for effect but this
should be pretty evident right away by the idle STFTs
going big in the right direction (or wrong).
Measuring my stocker F-body MAF (saved as virgin) the
sense resistor is 151 ohms, pretty close to the truck/SLP
unit. The two that line up are 9.5 ohms, the 150 ohm
one is the one to shunt for richer (requiring more power
to get to same resistance hence indicating more airflow).
them very reliable especially in high-vibe environments.
The DIP switch you can see what you get, the pot you
have to measure. In the end I've found it easiest to just
pull the MAF and solder a new fixed resistor in the little
case (most of the time is in MAF relearning, not adjusting).
Stock (F-body) MAF might want a different value. The
85mm truck MAF sense resistors are 157 ohms cold,
maybe 300 hot? That would make some sense for the
3K resistors to be making 10%-type changes. If your
F-body MAF has a higher or lower value you might start
with a different value. Also have to determine whether the
MAF resistor bridge is the same config or not, F-bofy vs
truck, so as to shunt the right one for effect but this
should be pretty evident right away by the idle STFTs
going big in the right direction (or wrong).
Measuring my stocker F-body MAF (saved as virgin) the
sense resistor is 151 ohms, pretty close to the truck/SLP
unit. The two that line up are 9.5 ohms, the 150 ohm
one is the one to shunt for richer (requiring more power
to get to same resistance hence indicating more airflow).
Originally Posted by BubaGumpShrimp
this is great new to me. I have been trying to tune the maf via ls1 edit and i go over the max range of programming. I ported my maf to the max(85mm) and descreaned it. LTFT went to +25. I was able to get the program to correct it down to +5 but no lower due to maxed out maf table. So i will give this a try and see if i can final tune with edit. Was also wondering if instead of hooking up resistors to dip switches, you could hook up an adjustable resistor (pot) sp?? and just change the value with a screwdriver. Cant see why that wouldnt work either...
