GM Engineers: Please settle MAF screen debate once and for all
ma...@*remove*pacbell.net
Nick Horianopoulos wrote:
>
> I keep hearing about the MAF screen debate, and I wonder why you would
> need a screen behind an air filter. Some say it exists to smooth airflow
> past the MAF, but I wonder if it is a holdover from the MAS from '93,
> and the guy that manufactures them for the St. Therese plant is a
> brother-in-law of the plant manager!
>
> Can we get a GM Engineer online to try an answer this debate?
> --
>
> Nikolai Padgordni
>
> (not really, but all my pals know who I am!)
Less filling!!! Tastes great!!! I don't think your gonna get an easy
answer on this one 'ole Nikolai. My *opinion* would be that the screen
looks more important than the door and window variety. The honeycomb
design looks almost functional (Elixrfixr once invoked the phrase,
"laminar air flow"). Something about reducing air turbulance before it
goes past the sensor wires? Mine's intact and is gonna stay that why
until someone else convinces me otherwise. One thing I know for sure is
that the camp seems evenly split on this one.
--
Steve Pottberg ma...@pacbell.net
'97 Camaro Z28 Auto 3.42 / T-Tops
K&N FIPK / HPP+ & 160° stat / Borla Cat-back
2.073 60' / 13.822 e.t. / 100.60 mph
http://www.geocities.com/MotorCity/Downs/4543/
cama...@themall.net
Hell!! Just pull it ALL off and throw on a Vic Jr. with a
Dominator...just a thought...:-)
Chuck
In article <5qphdd$cic$1...@nnrp4.snfc21.pbi.net>, magoo@*REMOVE*pacbell.net
says...
You guys talking about the screens on MAF sensors that TPIS and others
recommend getting rid of? Well, if you are....
I read somewhere (can't remember where) that they are there for cooling
purposes. Seems that when GM was initially doing testing (I guess on the
first MAF sensors) they did it out in the desert. Things tend to
overheat out in the desert, so they added the screen to help cool things
down. Ever since then, all MAF sensors have had 'em. I don't have a MAF
sensor (speed density car), so I don't have no screens either.
If that is not what you are talking about, then disregard this message.
Chuck
'92 GTA
DMoody8850
In article <MPG.e3b33631...@news2.thirdwave.net>,
ch...@pachuco.com (Chuck) writes:
>You guys talking about the screens on MAF sensors that TPIS and others
>recommend getting rid of? Well, if you are....
>
>I read somewhere (can't remember where) that they are there for cooling
>purposes. Seems that when GM was initially doing testing (I guess on the
>first MAF sensors) they did it out in the desert. Things tend to
>overheat out in the desert, so they added the screen to help cool things
>down. Ever since then, all MAF sensors have had 'em. I don't have a MAF
>sensor (speed density car), so I don't have no screens either.
>
>
Chuck, I believe you are mistaken. The cooling fins that you find in the
3rd gen MAF sensors are the items that were added to them to prevent them
from overheating. When TPIS modifies those old sensors, they remove the
screens AND mill out the cooling fins.
D.J. "Hammer" Moody
91 Mustang GT
94 Z-28 6 speed
97 Yamaha YZF1000-R check out the low down on this beast at: www.sirius.com/~mtrwrld/features97/yzf1000_97/Welcome.html
Lars
I'm not convinced about this theory. A MAF sensor works by measuring the
electricity required to keep the sensor element at a constant temperature.
Depending on how much air flow (and what temp the air is) one can calculate
the Mass of the passing air. IE more volume and colder/denser air cools
faster. I have my doubts that the screen could provide any cooling effect
or that it is even required.
--
Lars
http://www.flash.net/~ldennert
Chuck <ch...@pachuco.com> wrote in article
<MPG.e3b33631...@news2.thirdwave.net>...
> I read somewhere (can't remember where) that they are there for cooling
> purposes. Seems that when GM was initially doing testing (I guess on the
> first MAF sensors) they did it out in the desert. Things tend to
> overheat out in the desert, so they added the screen to help cool things
> down. Ever since then, all MAF sensors have had 'em. I don't have a MAF
> sensor (speed density car), so I don't have no screens either.
>
The Lunce
> Less filling!!! Tastes great!!! I don't think your gonna get an easy
>answer on this one 'ole Nikolai. My *opinion* would be that the screen
>looks more important than the door and window variety. The honeycomb
>design looks almost functional (Elixrfixr once invoked the phrase,
>"laminar air flow"). Something about reducing air turbulance before it
>goes past the sensor wires? Mine's intact and is gonna stay that why
>until someone else convinces me otherwise. One thing I know for sure is
>that the camp seems evenly split on this one.
>--
>Steve Pottberg ma...@pacbell.net
>'97 Camaro Z28 Auto 3.42 / T-Tops
>K&N FIPK / HPP+ & 160° stat / Borla Cat-back
>2.073 60' / 13.822 e.t. / 100.60 mph
>http://www.geocities.com/MotorCity/Downs/4543/
>
>
Well, I'm keeping mine on. I've removed it and found that idle quallity
tends to suck. I will admit that it does improve WOT. But that isn't how I
usually drive to work! I would recommend removing it at the track and put
it back in when you leave. I also cut wider opennings under the air
filters and put in k&n's. Good enuf for me.
Bruce
Simon Lumley
I've got a book called 'How to modify and troubleshoot Chevy fuel
injection engines'. According to that the MAF was tested in the desert
and the heat gave problems, so they added some cooling fins on top of
the electronics (which you can see if you look up the barrel of the
MAF).
There is a mod to increase airflow by filing off the fins, but you
could easily trash the whole thing.
As far as I'm aware the screens just protect the element from flying
debris.
Simon.
'85 Z28
Chris J
On Tue, 29 Jul 1997 12:31:38 GMT, luml...@boat.bt.com (Simon Lumley)
wrote:
>As far as I'm aware the screens just protect the element from flying
>debris.
The "screen" on the MAF on my 89 Fbird is a honeycomb filter, which is
commonly used in the electronics biz to isolate components from
electromagnetic fields (RF, like comes from radar towers, tv stations,
etc.) so I suspect the filter has something to do with protecting the
MAF from RF fields. If that's so, removing it will tend to increase
the liklihood of the MAF failing in the presence of a strong RF field.
Just my .02 worth.
Chris J
Googolplex
Chris J (cjoh...@slonet.org) wrote:
: On Tue, 29 Jul 1997 12:31:38 GMT, luml...@boat.bt.com (Simon Lumley)
: wrote:
Well it's a good guess, but I would bet the house against it. I go for
laminar flow, to help precise readings.
Vellotti
I would like to add that in addition to removing the screen to increase
airflow, you can also take a die grinder and remove the heat sink (the
slotted die-cast metal) at the base of a MAF. This sink is not there on
some other Bosch applications and rumor has it that at the GM Proving
grounds in Arizona, the MAF was getting way too hot. But if you don't
live in such a hot climate, take out the heat sink and increase your dry
cfm by around 150.
JP
tplo...@rci.rutgers.edu
In article <01bc946f$57336d00$764c1ed1@lars>,
"Lars" <EMail_Addr_is@My_Website.Spam_Deterrent> wrote:
>
> I'm not convinced about this theory. A MAF sensor works by measuring the
> electricity required to keep the sensor element at a constant temperature.
> Depending on how much air flow (and what temp the air is) one can calculate
> the Mass of the passing air. IE more volume and colder/denser air cools
> faster. I have my doubts that the screen could provide any cooling effect
> or that it is even required.
> --
> Lars
That's not the only way that MAF sensors work. On the v6 motors, the
sensor measures the frequency that a special orange "film" vibrates at.
The higher the frequency, the more air is flowing thru the sensor.
None of my 3 sensors <sigh> that I've gone thru have had heat sinks
on them, so this might be just for the v8 ones that use the heat/cool
method.
(Sorry that this is old, I'm about ready to toss my newsserver)
-Tom
-------------------==== Posted via Deja News ====-----------------------
http://www.dejanews.com/ Search, Read, Post to Usenet
Ray Forceno
Do you even know what laminar flow is? Laminar flow occurs when the
Reynolds number is in the range of 50 to 1800 (these number are
approximate as every fluid mechanics book varies). The Reynolds
number is defined as fluid density (air is a fluid) times fluid
velocity times pipe or duct diameter all divided by fluid dynamic
viscosity times the gravitational constant, or Re=(p*V*D)/(u*gc). As
the Reynolds number increases above the previously mentioned range,
fluid flow becomes turbulent. According to boundary layer theory,
fluid flow at the boundary is equal to 0. So, the screens create
multiple boundaries, thus reducing the fluid velocity (also reducing
the Reynolds number). You may be correct, the screens may keep the
incoming air flow in the laminar region, but they reduce the total
volumetric flow capacity of the mass-air meter. To complicate things,
the air flow into and engine is pulsating, so the math gets even
trickier. Now my question, how does keeping the flow in the laminar
region increase the accuracy of the mass-air meter?
-Ray
Jerry Brown
> Chris J (cjoh...@slonet.org) wrote:
> : On Tue, 29 Jul 1997 12:31:38 GMT, luml...@boat.bt.com (Simon Lumley)
> : wrote:
>
> : >As far as I'm aware the screens just protect the element from flying
> : >debris.
>
> : The "screen" on the MAF on my 89 Fbird is a honeycomb filter, which is
> : commonly used in the electronics biz to isolate components from
> : electromagnetic fields (RF, like comes from radar towers, tv stations,
> : etc.) so I suspect the filter has something to do with protecting the
> : MAF from RF fields. If that's so, removing it will tend to increase
> : the liklihood of the MAF failing in the presence of a strong RF field.
>
snip
Whatever it is for, I just read an article in some rag called HI Tech
Performance, September 1997 issue. This article documents a bunch of mods
to the MAF on (I believe) a 97 Z 28 Camaro. They chopped up the box that
the MAF sensor sits in and modified the heck out of the MAF including
removing the screen. They claimed some measured gain, I can't remember
exactly how much ( seems like they were talking 4 HP) since I was reading
the magazine in a dept store while waiting for my windshield to be
repaired.
Jerry Brown
96 FBird
SLOPEZ12
>Please settle MAF screen debate once and for all
>Do you even know what laminar flow is?
This probably won't settle it, but
-sense someone wants to show how smart they are-
-Reynolds # Hah! - must be an engineering student
The maf works by inducing a current to flow through a platinum wire.
The air flow cools the wire which changes it's resistance.
The amount of oxygen present in the air changes the amount of cooling of
the wire. The resistance of the wire is proptional to the
oxygen flowing by it. You can figure the rest out.
The honey comb structure and laminar air flow sounds good.
But I don't know.
IF swirling were to occur, possibly this could change the reading.
The pulsing is smoothed by the plenum volume and averages out
at 100revs per second with the wire being considerably larger than an
oxygen molecule.
Scott
Part time engineering student
Googolplex
Ray Forceno (rforceno*SPAMFREE*@jersey.net) wrote:
: On 30 Jul 1997 04:53:45 GMT, goog...@ripco.com (Googolplex) wrote:
: >Chris J (cjoh...@slonet.org) wrote:
: >: On Tue, 29 Jul 1997 12:31:38 GMT, luml...@boat.bt.com (Simon Lumley)
: >: wrote:
: >
: >: >As far as I'm aware the screens just protect the element from flying
: >: >debris.
: >
: >: The "screen" on the MAF on my 89 Fbird is a honeycomb filter, which is
: >: commonly used in the electronics biz to isolate components from
: >: electromagnetic fields (RF, like comes from radar towers, tv stations,
: >: etc.) so I suspect the filter has something to do with protecting the
: >: MAF from RF fields. If that's so, removing it will tend to increase
: >: the liklihood of the MAF failing in the presence of a strong RF field.
: >
: >: Just my .02 worth.
: >: Chris J
: >
: >Well it's a good guess, but I would bet the house against it. I go for
: >laminar flow, to help precise readings.
: >
: > goog...@ripco.com
: Do you even know what laminar flow is? Laminar flow occurs when the
: Reynolds number is in the range of 50 to 1800 (these number are
: approximate as every fluid mechanics book varies). The Reynolds
: number is defined as fluid density (air is a fluid) times fluid
: velocity times pipe or duct diameter all divided by fluid dynamic
: viscosity times the gravitational constant, or Re=(p*V*D)/(u*gc). As
: the Reynolds number increases above the previously mentioned range,
: fluid flow becomes turbulent. According to boundary layer theory,
: fluid flow at the boundary is equal to 0. So, the screens create
: multiple boundaries, thus reducing the fluid velocity (also reducing
: the Reynolds number). You may be correct, the screens may keep the
: incoming air flow in the laminar region, but they reduce the total
: volumetric flow capacity of the mass-air meter. To complicate things,
: the air flow into and engine is pulsating, so the math gets even
: trickier. Now my question, how does keeping the flow in the laminar
: region increase the accuracy of the mass-air meter?
: -Ray
I've just been speculating, as I said. Here, I'm just a lowly E.E. but You
wanted to show off...so answer it yourself. My opinion stands. By the way,
liquid Helium is a super-fluid that does not have a boundary flow of zero.
--
Greg Banish
>
> : Do you even know what laminar flow is? Laminar flow occurs when the
> : Reynolds number is in the range of 50 to 1800 (these number are
Re(C) for a pipe is ~3000...
Now that that's settled, we must also realize that the flow inside the
intake tracts isn't *completely* laminar. However, it is most certainly
close enough for the the MAF to get a 3sigma approximation of the flow.
(Q=VA, from continuity principle and the area, A, is constant)
This being said, the screen *IS* in there as a flow straightener. It
doesn't make the flow 100% laminar, but it makes it close enough for the
MAF to get an accurate reading. Taking the screen out allows the flow to
trip more, allowing backflows and areas of artificially high velocity.
This can mislead the MAF to thinking it has more or less airflow than is
actaully there. This is why cars with these screens removed often run
poorly of idle, when flow is least stable.
~gb
'93 LX
GMI Enineering & Management Inst.
Senior II, Mechanical Engineering, Automotive Specialty
Phil G.
Bottlebob wrote:
>
> Greg Banish wrote:
> >
> > >
> > > : Do you even know what laminar flow is? Laminar flow occurs when the
> > > : Reynolds number is in the range of 50 to 1800 (these number are
> >
> > Re(C) for a pipe is ~3000...
PLEASE! Don't make me get my Fluid Dynamics notes out! I don't want to!
> >
> > Now that that's settled, we must also realize that the flow inside the
> > intake tracts isn't *completely* laminar. However, it is most certainly
> > close enough for the the MAF to get a 3sigma approximation of the flow.
> > (Q=VA, from continuity principle and the area, A, is constant)
> >
> > This being said, the screen *IS* in there as a flow straightener. It
> > doesn't make the flow 100% laminar, but it makes it close enough for the
> > MAF to get an accurate reading. Taking the screen out allows the flow to
> > trip more, allowing backflows and areas of artificially high velocity.
> > This can mislead the MAF to thinking it has more or less airflow than is
> > actaully there. This is why cars with these screens removed often run
> > poorly of idle, when flow is least stable.
> >
> > ~gb
> > '93 LX
> > GMI Enineering & Management Inst.
> > Senior II, Mechanical Engineering, Automotive Specialty
>
> Greg Banish:
>
> Nice informative post. Three months in replying isn't exactly a timely
> response though, is it?
>
> Bottlebob
I never commented on this one in the first place, as my '71 Camaro (the
only car I have that's on-topic for this NG) doesn't have FI (yet)...
I was going to make my own Ram Air kit for my Grand Prix until thinking
about the flow paths in the piping gave me a headache.
I still may do it...
Phil.
Bottlebob
Greg Banish wrote:
>
> >
> > : Do you even know what laminar flow is? Laminar flow occurs when the
> > : Reynolds number is in the range of 50 to 1800 (these number are
>
> Re(C) for a pipe is ~3000...
>
DMoody8850
In article <63rv56$kbs$4...@gail.ripco.com>, goog...@ripco.com (Googolplex)
writes:
>I made mention of the date of reply to this guy too...since he sent this
>identical post to me in E-Mail. I further took exception to his story that
>cars without screens "often" run poorly at idle. Mine doesn't; nor do I
>think
>this is true for the majority of people whose posts I've seen.
>
>
>goog...@ripco.com
>
>
My Z-28 doesn't run poorly at idle either. I shall add though, my
Mustang did get a slight roughness in idle when I removed the screen from
it's MAF.
Hammer
Come check out House Of Hammer at:
http://members.aol.com/dmoody8850/index.html
Greg Banish
On Wed, 5 Nov 1997, Bottlebob wrote:
> Nice informative post. Three months in replying isn't exactly a timely
> response though, is it?
>
Sorry, I haven'y been exactly on top of the NG lately. ..just trying to
help...:)
~gb
Tom P
At the risk of beating the hell out of a dead horse, here
goes my experience with the MAF screen:
I've got the 2.8l Firebird (as you all know, <grin>). My
air intake is a "bent" one (ha), and right between the
MAF and air filter is a (guessing) 45 degree bend. When
I pulled the screen, the car wouldn't start right away.
It started (3rd try, maybe?), and the computer set the
code for "MAF- low frequency", meaning a low air flow.
With the screen back in, the car started right up, and
the code went away.
It seems that because of the bend in the Firebird 2.8 MPI
intake, the air was rushing -around- the sensor's film
instead of over it. I'd guess the same would go for
the Firebird TPI v8's air going around the sensor's
hot wire- but I don't know- the v8's hot wire sensor
might act differently then the v6's frequency film
sensor.
From what I hear, there aren't problems with pulling the
MAF screen from a 3rd gen Camaro 2.8, probably because
of the "straight" air intake system. In fact, my GM
Helm's service manual says that the screen is there
to "smooth airflow over the sensor".
-Tom P
1986 Firebird SC: 173 (2.8l) v6, rebuilt 700r4, 3.42 rear,
Accel Supercoil/cap/rotor, MSD 8.5mm wires, Splitfire plugs,
Summit fuel filter/gauges, K&N Filtercharger, ADS street chip,
B&M Megashifter/Supercooler/Stage 2 Shift kit/Overdrive sleeve,
Dynomax 2.5" hi-flow cat/super turbo, modded MAT/TB/air box,
TCI v8 radiator, Energy Suspension bushings
Chateau LindaMar
Just want to let you know that your informative reply was greatly
appreciated. As an engineer with a global computer company I *know*
how hard it is to find time to give good technical help in ng's. I
frequently find myself perusing the ng's that cater more to my hobbies
or interests other than those relating to my profession, unless, of
course, it is my job to monitor a ng. Thanks in advance for any
future help you may offer. -Mark
Greg Banish wrote in message ...
