maf,WHICH ONE TO GO WITH.!
06-07-2004, 05:59 PM
#1
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maf,WHICH ONE TO GO WITH.! ok guys, got all my modes done,224/224cam, headers,slp flow pak. gears, tranny upgrade,now I need advice on a bigger maf,If I go up a notch bigger on the maf, will I need to retune and what size should I go with and what about the screen,Ihope I dont have to get it retuned ,BUT.oh btw my car Is a 2002 collecters ed. ta. thanks. 
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06-07-2004, 10:04 PM
#8
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Don't decreen it because it'll run too lean without tuning, and it'll be a bitch to tune to. The screen is what makes the MAF accurate, and an inaccurate MAF is a bad thing.
06-07-2004, 10:38 PM
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I flow tested two screened truck MAFs in tandem
and they read within about 100Hz of each other
(same tube = same airflow). I descreened one and
did it again, no change.
Where the screen matters, is when you have an
intake tract that is not nice and straight. Then
you can have airflow bias across the MAF face
and all bets are off.
But the screen does not, in the absence of such
error sources, have boo-diddly to do with MAF
accuracy. It does however induce a measurable
pressure drop at higher flows which subtracts
directly from your high RPM MAP and your max
cylinder charge. The F-body intake tract is a
pretty straight shot.
As to the original question, the only MAF out
there I have seen, which is close to mixture-
neutral (not needing tuning) is the SLP '01-'02
version 85mm. NOT the '98-'00 version. People
buy the '01-'02 and then say "it made no difference".
Well, exactly. It's tuned (pretty close to) stock
by the resistor they put on there. I run this one
(descreened and somewhat modified) with near
perfect LTFTs and O2s. I changed the resistor
to account for my file-porting it. Did it do anything
for me? Probably not much. But, I know it's as big
as you're going to get and is not a significant
source of mixture error or pressure drop. Which is
about all you could ask of a MAF.
The problem really is in expectations. The stock
MAF is a restriction on the order of the stock lid.
The airflow related performance gain is of the
same order. But unlike the lid, there are side
effects to be avoided by choosing some over
others, and a no-cost option (descreen) that is
plenty good enough for your average F-body.
But who wants to be average when there's a
full page glossy ad for $399 worth of guaranteed
(see disclaimer) superiority staring you in the
face?
and they read within about 100Hz of each other
(same tube = same airflow). I descreened one and
did it again, no change.
Where the screen matters, is when you have an
intake tract that is not nice and straight. Then
you can have airflow bias across the MAF face
and all bets are off.
But the screen does not, in the absence of such
error sources, have boo-diddly to do with MAF
accuracy. It does however induce a measurable
pressure drop at higher flows which subtracts
directly from your high RPM MAP and your max
cylinder charge. The F-body intake tract is a
pretty straight shot.
As to the original question, the only MAF out
there I have seen, which is close to mixture-
neutral (not needing tuning) is the SLP '01-'02
version 85mm. NOT the '98-'00 version. People
buy the '01-'02 and then say "it made no difference".
Well, exactly. It's tuned (pretty close to) stock
by the resistor they put on there. I run this one
(descreened and somewhat modified) with near
perfect LTFTs and O2s. I changed the resistor
to account for my file-porting it. Did it do anything
for me? Probably not much. But, I know it's as big
as you're going to get and is not a significant
source of mixture error or pressure drop. Which is
about all you could ask of a MAF.
The problem really is in expectations. The stock
MAF is a restriction on the order of the stock lid.
The airflow related performance gain is of the
same order. But unlike the lid, there are side
effects to be avoided by choosing some over
others, and a no-cost option (descreen) that is
plenty good enough for your average F-body.
But who wants to be average when there's a
full page glossy ad for $399 worth of guaranteed
(see disclaimer) superiority staring you in the
face?
06-08-2004, 10:24 AM
#11
TECH Senior Member
Those are words that are INCORRECT. There isn't a damn thing wrong with descreening a MAF. Why does this urban legend resurface all of a sudden today? 
PORTING the MAF alters the signal. Descreening DOES NOT alter it to any appreciable degree therefore it doesn't throw off the tuning.
I agree with everything Jimmyblue said above.
The following statements are completely FALSE...
"Don't decreen it because it'll run too lean without tuning (you obviously haven't tested this.), and it'll be a bitch to tune to (there will be NO change). The screen is what makes the MAF accurate, (it will be no less accurate without the screen.)"
It's obvious that peope are getting descreening confused with PORTING the MAF which can certainly cause several problems (altered Ltrims, a leaner mixture at WOT, increased timing advance, lowered tranny line pressure.) Let's not simply regurgetate what we think we now know from our reading. When in doubt, post personal experience only.
FWIW, GM removed the screen on the ZO6.
PORTING the MAF alters the signal. Descreening DOES NOT alter it to any appreciable degree therefore it doesn't throw off the tuning.
I agree with everything Jimmyblue said above.
The following statements are completely FALSE...
"Don't decreen it because it'll run too lean without tuning (you obviously haven't tested this.), and it'll be a bitch to tune to (there will be NO change). The screen is what makes the MAF accurate, (it will be no less accurate without the screen.)"
It's obvious that peope are getting descreening confused with PORTING the MAF which can certainly cause several problems (altered Ltrims, a leaner mixture at WOT, increased timing advance, lowered tranny line pressure.) Let's not simply regurgetate what we think we now know from our reading. When in doubt, post personal experience only.
FWIW, GM removed the screen on the ZO6.