[s-cars] MAF screen removal-please explain

[Mark Strangways]

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I understand it that a venturi, modifies the air pressure based on it's flo=
w=2E
I didn't understand it that it modified the MASS of anything, though by inc=
reasing the pressure do you also increase it's mass due to the fact you hav=
e more mols in a given space ? If so, then I suppose the venturi would modi=
fy the mass of the air. While I have not opened my MAF, yet, I suspect it d=
oes not have a huge venturi effect. I may be wrong, in which case I will st=
and corrected.

You have a URL for the archives ?

Mark
  ----- Original Message -----
  From: QSHIPQ at aol.com
  To: strangconst at rogers.com ; mlped at qwest.net ; S-CAR-List at audifans.com
  Sent: Saturday, April 19, 2003 9:44 AM
  Subject: Re: [s-cars] MAF screen removal-please explain


  That's not how I see it, it's "if your pumps ancillaries can measure it c=
orrectly"....  More air doesn't necessarily translate to better engine perf=
ormance, you need to correctly measure it to make that claim.  Screen affec=
ts laminar flow and pressure accross a venturi.  There's a ton more on this=
 in the archives.  IMS, my discussions with a bosch dude, he said leave dem=
 alone, or at the very least leave the incoming side in.

  Mark, the mass that enters is the same, it's the measure of it that's cri=
tical to the properties of laminar flow.  The key is what ever tumbles (tur=
bulence) or other orientation passes the venturi wing is key to the MAF pro=
perly measuring that 100cfm.

  All in the archives...  From my sidedraft days (currently on my road rock=
et), I'm pretty convinced  from practical experience that anything you do i=
n front or behind a venturi, affects its measure of air.  In terms of a MAF=
, that would also affect it's measure of air mass.  For a simple experiment=
, put your house fan in front of the screen door, with a sail tape on the o=
ther side, then open the door.

  Yeeha, find that website MLP :)

  HTH and my .02

  SJ
  85 FJ1387 with Mikunis and small sreens, new jets...

  In a message dated 4/19/2003 8:02:53 AM Central Daylight Time, strangcons=
t at rogers.com writes:

  Snip.
  Now for part two, does removing the screen change the way in which the hot
  wire actually measures the MASS of air (not flow or velocity) passing
  through the meter?  I don't know.  I'm inclined to believe that it would,
  but I'd defer to the more sage advice of the engineering types on the lis=
t=2E
  /Snip.


  By removing the screens, you are NOT changing the MASS of air flow that
  enters the MAF for a given amount of air flow.
  You are just making it easier to get in / out. If the motor is drawing 100
  CFM, it will draw that thru the MAF, and will give the appropriate signal
  from the MAF, regardless of screens.

  As Hap pointed out, it's the 'Negative Boost'. By reducing any obstruction
  to with in the inlet stream, you increase the pressure available to the
  turbo, which equals more boost. Similarly by decreasing the pressure drop
  across the filter you increase boost.
  While decreasing pressure drops, you allow more flow. If you pump can acc=
ept
  it.

  At least that's the way I see it .

  Mark S

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