Stock MAF or SLP MAF?
07-09-2003, 08:12 PM
#21
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Re: Stock MAF or SLP MAF? Just the canned tune, and e-**** fiddling. Car ran fine (no
KR or ping) with the 0, 0 settings after installing the
canned tune. Also runs ping-free with the timing at +10%
power enrichment at +2%, which gives me the O2 voltage I'd
like to see at WOT (900-920mV). I have no exhaust mods but
the SLP CME that came with the 335HP SLP SS option and
have a cold air (standard SS) hood and a pretty steady 195F
coolant temp.
I'm thinking maybe the '98-'00 folks would be better off
with the '00-'02 MAF version and get their lean-out in
some more "surgical", alterable way than "take what you get"
from the supposed '98-'00 MAF. If you just -have- to swap
MAFs, that is.
The SLP 85mm (late) is the only MAF I'm aware of that
-only- increases face area and doesn't mess mixture
around on F-body LS-1s. Screened-vs-screened, you have
28% more face area and I figure this is a 22% reduction
in the pressure drop. I ballpark the max MAF drop at maybe
5" H2O (unscientific extrapolation from my shop vac flow
tests in which the stocker ran 2" drop). So maybe you
pick up 1" H2O manifold pressure from the reduced
restriction. By way of sanity check, I see 14.2PSI MAP
readings against 14.7 ambient (with the SLP, lid and
SS hood) which is a 14" H2O drop. Give 2" to the filter
and some to the hoses & TB, maybe the MAF accounts for
up to 10" H2O. Maybe you pick up 2" H2O MAP increase
with the bigger MAF.
1" H2O improvement in your MAP would give you maybe 0.75HP.
2" H2O? Maybe a pony and a half.
So 1.5HP or less. Any other power output improvement
comes from the tuning effects of a MAF. Buying a MAF that
"bends" your mixture is a single-shot-in-the-dark tuning
attempt, basically. At $85 used, maybe that's a bullet
you'd throw some mad money at. I did, and got lucky
(no problems for my cash). But $399, new? Find a more
flexible tool for tuning, that hasn't caused so many,
so much grief. Heck, pop the screen (for that same
pony and a half) and buy a Predator if you like to fiddle.
And fiddle with the MAF orientation to see whether the
new airflow imbalance (across face, from lack of flow-
straightening, -leveling screen) has a "sweet spot"
that helps more than hurts, somewhere.
I can see it now... another "forever thread" of people
trying to find the "magic MAF angle"
KR or ping) with the 0, 0 settings after installing the
canned tune. Also runs ping-free with the timing at +10%
power enrichment at +2%, which gives me the O2 voltage I'd
like to see at WOT (900-920mV). I have no exhaust mods but
the SLP CME that came with the 335HP SLP SS option and
have a cold air (standard SS) hood and a pretty steady 195F
coolant temp.
I'm thinking maybe the '98-'00 folks would be better off
with the '00-'02 MAF version and get their lean-out in
some more "surgical", alterable way than "take what you get"
from the supposed '98-'00 MAF. If you just -have- to swap
MAFs, that is.
The SLP 85mm (late) is the only MAF I'm aware of that
-only- increases face area and doesn't mess mixture
around on F-body LS-1s. Screened-vs-screened, you have
28% more face area and I figure this is a 22% reduction
in the pressure drop. I ballpark the max MAF drop at maybe
5" H2O (unscientific extrapolation from my shop vac flow
tests in which the stocker ran 2" drop). So maybe you
pick up 1" H2O manifold pressure from the reduced
restriction. By way of sanity check, I see 14.2PSI MAP
readings against 14.7 ambient (with the SLP, lid and
SS hood) which is a 14" H2O drop. Give 2" to the filter
and some to the hoses & TB, maybe the MAF accounts for
up to 10" H2O. Maybe you pick up 2" H2O MAP increase
with the bigger MAF.
1" H2O improvement in your MAP would give you maybe 0.75HP.
2" H2O? Maybe a pony and a half.
So 1.5HP or less. Any other power output improvement
comes from the tuning effects of a MAF. Buying a MAF that
"bends" your mixture is a single-shot-in-the-dark tuning
attempt, basically. At $85 used, maybe that's a bullet
you'd throw some mad money at. I did, and got lucky
(no problems for my cash). But $399, new? Find a more
flexible tool for tuning, that hasn't caused so many,
so much grief. Heck, pop the screen (for that same
pony and a half) and buy a Predator if you like to fiddle.
And fiddle with the MAF orientation to see whether the
new airflow imbalance (across face, from lack of flow-
straightening, -leveling screen) has a "sweet spot"
that helps more than hurts, somewhere.
I can see it now... another "forever thread" of people
trying to find the "magic MAF angle"
