Scottiewitdabody

i took off the screen in front of my mass air flow sensor and now the check engine light is on is there anyway to get that light to turn off???

IROCZTWENTYGR8

iTrader: (1)

A new MAF.

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Looking For:

87 IROC-Z 350 TPI
84 TRANS AM 305 H.O.

FormulaKid

Did you remember to connect the plug back onto the MAF?

Scottiewitdabody

the only reason i tookthe screen off is because i got this tip from www.iroczsource.com:

[5HP] MASS AIR FLOW SENSOR
Remove the screen in the front of mass air flow sensor for about 15 horsepower. Visitors who have tried this just love the increase in throttle response and top end power

IROCZTWENTYGR8

iTrader: (1)

U should have asked or done a search 1st before doing that, because lots of times some1 does this and doesn't do it right or messes up and than u need a new MAF, u can't fix them once u mod the MAF. If u would have just asked 1st, u could have got lots of information on this, and unless u have a 305 with a S/C, or a high flowing 350 or more, its not going to do much if anything.

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Looking For:

87 IROC-Z 350 TPI
84 TRANS AM 305 H.O.



[This message has been edited by IROCZTWENTYGR8 (edited February 27, 2001).]

Steve89GTA

If you DID remember to plug the connector back in and are still getting the SES, check the thin wire that's located in the middle of the unit (within the circle). If it's broken in any way, you'll need a new one...and they're not cheap.

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89 GTA G92
305 TPI WC 5spd w/3.45
Accel Cap & 8mm Taylor's
Custom 4" Cold Air Induction
Jet Airfoil
K&N Airfilter
160 deg stat/fan switch TB Bypass - Steel Rad
Cat back 3" Exhaust w/Terminator Muff.
HiGh FlOw Dynomax Cat
Spohn LCA's - KYB GR-2's
Autometer Vac+Oil Temp

Vader

DAMN! Another case-in-point to archive in my "Why NOT to remove MAF screens" log book. There are very few engines that need more MAF flow than the stock unit can deliver, and too many possible problems from removing the screens.

I don't want to go into the entire three-page text of air flow, molecular mass and velocity, turbulence and laminar flow, and what removing the screens can do to F-up your intake air flow through the sampling tube, but you now have an example of what can go wrong. Suffice it to say that even if the hot wire is not borken, the air might now be flowing around the tube instead of through it.

Check a Wells SU-145 replacement sensor if your has taken the big dive. Before you do, make sure the sensor housing is sealed to the ductwork and there are no cracks or splits in the ducts after the MAF.

Good luck.

Incidentally, send your "Thank You" card to the site you mentioned - the one that said you'd get 15 HP from screen removal (Ha! For me to POOP on!) If you get 15 HP from screen removal, you've got other flow problems as well, and you'd better start shopping for a different throttle body.

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Later,
Vader
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"No matter how hard you try you can't stop us now..."

IROCZTWENTYGR8

iTrader: (1)

LOL!!

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Looking For:

87 IROC-Z 350 TPI
84 TRANS AM 305 H.O.

John in RI

iTrader: (167)

I recently got burned on the purchase of a set of wheels by one of the guys on the IROCZSOURCE website,...... a whell was described as having a "nic" in it and once it was delivered I founf the "nick" to be a 3" dent in the wheel.

There's not many nice things to say about this site - Even the moderator blew me off when I included him in my attempts to resolve my mess.

John in RI
berlinetta@prodigy.net

MikeInAZ

How many times have we seen "Took out my screens, now code 33 ...vs..."took out my screens gained major HP.

It just doesn't happen and it's not worth it. If MAF airflow were a problem GM could have remedied this with 10 cents more plastic and made larger diameter parts and they could have saved major bucks overall just eliminating the screens.

These screens aren't just to keep grasshoppers out. The back screen will HELP in the event of a backfire from a lean condition. It may not be a sure bet BUT without the screen what do you have?

Just try this: take the little nut off your faucet at home and remove the aerator screen. Turn on the faucet. Do you have more flow.....YES. But you also have more turbulence. Turbulence inside the MAF with the microscopic thin metering wire is not a good thing. These screens also help regulate the airflow so it can be more accurately measured.

Vader, thanks to you for pointing this very important opinion out. In the past I have felt like a minority in debating screen issues. The proof is just not there that the good outweighs the bad. It takes one heck of a breathing engine to warrant more airflow at the MAF point and if you had that type of engine you probably wouldn't even be running with the MAF system.

Guest

Theres actually less with the screen out, common misconception. Thats how the aerator works, its so turbulent it breaks up the water and pulls some of the outside air into the water as it flows out of the faucet.

gta324

If the MAF isnt broke, you could try to reset the ECM. After gutting my MAF I also got error code and it helped me out, then I sold my Bosch MAF and got a Wells instead for less money

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GTA -89:Free flow muffler,dual 3" HF cats, Edelbrock headers, Vette heads, 1.52 RR 7/16, ZZ-9 cam, Big Mouth, AS&M LTR, !plenum, 52 TB, MSD 6AL, TPIS level V prom, Superior shift-kit and all the minor mods, a Canfield headed 383 in the works!! ready May 2001...ok..june...
http://www.itv.se/tacs/members_cars/m279/m279.html (Swedish Trans Am Club)

MikeInAZ

Dang your hide Madmax....you always make me get so precise........LOL.

OK, scratch the word turbulence....bad choice.

Screens In: Your faucet or MAF = more consistent, balanced airflow.

Screens Out: Your faucet or MAF = less consistent, more erratic, less balanced airflow.

In: Stabilized
Out: Less Stable

okfoz

NOT to argue, but let us consider some things.
When you take the MAF screens out, you are freeing up the air to travel less restricted thru the air-intake.
Since I also have a 90 Riv with a MAF, and my GM 87 Firebird Repair manual does not have this information I had to borrow it from a GM 90 Riv repair manual, the concept is the same no matter what car you drive with a MAF.

And I quote:
The air flow (volume of air) is determined by the Mas Air Flow (MAF) sensor. By applying a current to the grid inside the MAF to maintain a conasant grid temperature of 75°F, the ECM can calculate the tempreture and amount of air in grams per second entering the engine. As the amount of air past the grid increases, it has a cooling effect and more current must be applied to maintain a constant grid temperature. The ECM measures this change in current and calculates the temperature and amount of air in grams per second entering the engine. The system is sensitive to very minor changes, such as occur when a vacuum line is disconnected."

What the screens may do is to mix up the air, so it has a more consistant temperature. When the screens are removed it increases airflow, BUT the consistancey of the air changes. Someone above mentioned that it might be traveling around the tube in the center, which could be a posibility.

I have considered removing the second screen from the MAF, which would remove some turbulance out the air a little. I am not sold on the idea yet.

By the way... someone mentioned another MAF sensor other than the stock BOSCH, where would I be able to get one of those?? Is it larger?

John

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87 Formula Yellow/Black
Engine & Transmission
.040 over 5.0 converted to TPI, 9.5:1 Compression, SLP Cam Dur 206/212, Lift 480/487, Cent Line 112, SLP headers, SLP cat-back exhaust, K&N Airfilter, Modified Stock cold air intake, Ported & polished Stock TPI intake, Holley Adjustable Fuel Press regulator, AC Rapidfire Spark Plugs.
Gil Younger (no yo-yo) Shift Kit, Aluminum Driveshaft, 3.73 Posi gear
Suspension & Brakes:
Baer 12" brakes 4 wheels, KYB AGX Adjustable Shocks & struts, Hotchkis strut tower brace, South side machine frame connectors, Custom reinforced control arms and pan hard bar.
Interior:
Custom Leather interior, CUSTOM Yellow Gauge Faces, Kenwood Receiver, Pioneer Speakers, Kicker Substations, Kenwood 10 Disk Changer, Pioneer Amp.

87 Formula TPI (5 Speed) Yellow/Gray STOCK

1967 Buick Riviera 430hp Turns high 14's (Not bad for 4300 lbs)

83 Camaro (Parts)
83 T/A (parts)

http://www.3rdgenformula.com

Guest

Normal airflow in a tube ideally has a parabolic curve from no velocity at the edges, to max velocity in the center of the tube. This is called laminar flow. The screens on the MAF disrupt the airflow, and turn the flow into turbulent flow, which is more of a straight line across the tube where the velocities are all the same. The velocity affects the airflow past the heated wire, and therefore affects how much the wire is cooled. The air temperature doesnt matter, its wouldnt be different enough across the tube for the MAF to be able to see it.

As an example, if you had a 100' long tube before and after the MAF, taking the screens out would not matter at all as long as the MAF was calibrated for the airflow it is seeing since the heated wire is in the center of the tube. Recalibrating the airflow charts in the ecm to compensate for the change in the car with shorter and more realistic sized tubes is entirely possible. The TA's stock intake has a bend right before the MAF, and this will affect where the actual max velocity is, not to mention its somewhat turbulent as it is. The setup on the Z28/Iroc's is better but there is still a transition area close to the MAF where the area of max velocity may not be (and probably isnt) in the center of the MAF. Due to the way air flows dependant upon speed, it is reactive to RPM and the location of where the max velocity is could very well change depending on the engine speed.

IMO, the MAF is far from accurate enough to worry about such small changes. The largest change is taking the screens out, where the airflow lies after that has little effect that cant easily be remedied with a scan tool and some changes in the chip.

The other MAF mentioned is made by Wells, I dont think its larger (or at least not considerably... its supposed to fit in the stock location) but it flows more air and has a better way of measuring airflow. It has a screen as well, and if you remove that one you may as well leave the MAF off the car entirely since it will be useless.

[This message has been edited by madmax (edited June 25, 2001).]

MikeInAZ

Madmax, my following of your post goes way back as does our third gen mutual interest. I have gained help from you on many post so please understand that it is WITH the greatest respect for you that I disagree with you.

Please also understand that these are just my findings, and I'm not trying to argue, match wits, or even to debate ....it's just I'm talking and I can't shutup .....LOL.

Airflow into a tube is anything but normal for the purposes of MAF calibration. That is where the 1st problem lies. Air traveling at the walls of the tube (boundaries) is slowed down by the walls whereas the center, unrestricted air, does not encounter this drag and thus creates the parabolic curve of airflow you speak of.

More precisely: Low to medium flow the air is profiled in a parabolic flow shape with the walls of the flow almost stopped and the center section going the fastest, as you say.

During high flow, the air is profiled in a turbulent, tumbling flow shape with the vortices or swirls near the wall of the tube, with the majority of the center of the flow almost parallel.

The average velocity of the steam is predictable, although any finite point may be going any direction. Random turbulence may break out at any point.

This unrestricted, unrestrained flow of air is defined as "turbulent airflow".

Turbulent airflow and Laminar airflow are opposites.

It is the introduction of the 2 screens that is creating (or trying to) the ideal situation (for MAF measuring purposes) of laminar (smooth, even & consistent) airflow.

IS THIS RESTRICTIVE - ABSOLUTELY, but by design.

A voltage regulator restricts voltage to be contained within a certain range as does a fuel injector restricts fuel from being dumped in at random amounts.

So it is in this sense that the MAF screens are acting as what they were designed to do....regulate airflow.

By establishing this controlled airflow you have established a ground zero reference point by which you can do something productive with it like measure the amount of air being inducted into your engine.

My point of all this riff-raff is to substantiate (or try) my belief that the screens in a MAF are in fact the MOST important part of the MAF and to do away with them you might as well just chunk the MAF.

The screen straightens the flow and forces a uniform flow over the sensor wires to measure the amount of voltage required to maintain a constant temperature. The resulting voltage is converted into a frequency for a digital output. The varying frequency is then referenced to a set of lookup tables.

Without the screen, the computer can not take a correct reading on how much air is entering the engine.

When you port the MAF housing and/or remove the screens you are causing air to move by the sensors that is not being measured. More mass air is entering the car than what is measured. Lower frequency outputs are being read by the lookup charts and the calculations are based on lower than actual loads and lower than actual airflow.

This makes the ECM lean out the fuel mixture and add timing. Then the oxygen sensors read the lean fuel mixture and bump it back up to compensate for the MAF sensors low readings.

This puppy is so accurate that in early designs it was found that even the pleats in the stock filters vs. aftermarket filters made a difference in the readings as well as in some designs of MAF's a hexnut was used to replace a wingnut to hold a certain component because the wingnut shape was found to have a significant impact on MAF flow and readings.
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Above this line are a mixture of some of my opinions and various information retrieved from various MAF studies available on the internet. Below this line is my point and opinion.
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My point in all this rambling? Is to ask why? Why would someone remove a perfectly working component that is doing exactly what it was designed to do and invite all the potential problems that it might bring?

When in fact the stock MAF can outflow the stock TB and Intake setup.

I know they exist but I have never known of anyone that has received a substantial gain of HP from this mod and yet I can't count the number that have recieved a code 33.

IMHO Guys - One word - DON'T

Guest

I think you are searching for a different term thats more appropriate, steady state or steady flow. And usually the result is that more air passes across the sensing element, causing a high flow reading and hence the code 33. I tend to confuse 33 and 34 too...


There is in fact no such thing as laminar flow, its an ideal situation that fails to exist in real life. Laminar flow is often described as I did, its not truly free of turbulence but its as close as we can get. Teflon lined pipes and other smooth walled tubing is an attempt to create a truly laminar flow, but its still a parabolic curve rather than a straight line, constant velocity flow across an entire tube top to bottom. I suppose I should have clarified that first.

A fluid moving through a straight tube with no obstructions and restrictions (read:screens) is as close to laminar flow as anyone will ever see. The screens introduce an obstruction in the path of the fluid, and since they are not NASA shaped but round, there is a vortex on the opposite side of low pressure that causes turbulence. Theres probably upwards of 100 round strings across the airflow, thats turbulence*100. Turbulence isnt necessarily bad but it does limit the flowrate and thats something it seems we are all trying to find a way around. Is it worth it? Thats a question we all have to decide whenever we think about changing a part of any sort, and the risk involved in doing so. Ive taken so many screens out and never had a problem, I dont think twice about it. Maybe its luck, but I dont think thats it. I too have heard of many people doing the same thing (or so they say) and then the next thing you know its code 33. Those people should probably keep their fingers off the hood release, or at least know their limits.

The whole idea of a calibration table is to compensate for the fact the system is far from ideal. Even with the screens, air speeds cause the flow and the path of the flow to vary. Take a TA as an example, there is a bend right before the MAF, either a 45 on the eariler ones, or a 90 on the later ones. No fluid likes to turn. This causes the airflow to become anything but laminar, and theres all sorts of high and low pressure areas where of course the airspeeds vary widely. The screens are an attempt to break up the high pressure areas enough to make the flow across the entire area a little more equal so the MAF doesnt see a false reading dependant upon RPM. Its simply a crutch, nothing else. If you were to change the tables to the correct readings for each range, then everything would be just fine. Its just a matter of calibrating the meter so that it reads the flow correctly throughout flow ranges. The only difference the screens make is that its easier or maybe even unnecessary to calibrate the meter from what it would theoretically read at different flow rates. In some cases it may be necessary to recalibrate and in those instances you have to have a way to do it... not something we all have access to.

I agree with you about why you would want to mess with a working component, but then if I take that a step further, you shouldnt change anything at all under the hood... even the hex nut holding the aircan together with a wingnut you have laying in the parts bin.

JoelOl75

I completly dissected my MAF (screens and fins) and never set a code. TPIS sells them. They 'claim' (I know there's alot of TPIS haters out there ) removing the screens and fins causes less air to be sampled, but the difference is not linear and WOT is leaned out the most which is a good thing because the stock chip is rich at WOT. This could be further tuned with AFPR or custom chips.

In a nutshell I have 2 modded mafs and never set a 33 because of the maf (that's why I have 2 ) It was the plug, repeated unpluggin' spread the contacts out and set the 33. I'd seriously go through the flowcharts before condemning the maf, especially if you handled it nicely and the platinum wire is intact.

MikeInAZ

I love MAF topics.....Madmax and Xman....make no mistake I admire anyone who has made a free mod, gained performance, and NOT screwed up their car. It appears that you both have and I remember debating this topic with "Willie" and it seems he has also.... probably many others.

The reason I highly don't recommend it is folks like you guys are a rarity. I would venture to say that 90% screw up their cars for a zero gain.

Now I've got this other brainstorm..... our air filters are bound to be as restrictive as our mafs .....aren't they?

Guest

You have an 86 TA too, right? Take a look at your filter sometime... You will find out that the stock filter is about 85% useless, as most of the air is sucked through the filter through a 3-3.5" diameter area where the tube runs up to the MAF sensor. If that isnt restrictive, I dont know what is.

MikeInAZ

Yep 86 and you're right very poor design air cannister and very "Mod" unfriendly. Vader came up with about the best air can mod I've come across for an 86 to increase flow but it still doesn't change the diameter you speak of.

Vader

Don't. The rear screen is placed there to protect the fragile hot wire sensing element from sonic shock waves caused by both lean backfire and the "howl" you hear from teh intake valves popping open at WOT. A few good shock waves and your sensor could be toasted. Many sensors survive this modification, and many don't.

Wells Manufacturing Corp. offers a replacement MAF sensor that uses a thick-film sensor in place of the hot wire. It also uses a flat metal matrix in place of the round wire screen to ensure a correct average sample across the entire sensor array. There is only one matrix at the front of the sensor since the thick-film unit is immune to shock and vibration. Both of these improvements were "borrowed" from the design of the LT1 MAF sensor.

The I.D. of the sensor body has also been increased from the 70mm of the Bosch unit to a minimum of 73mm at the smallest point on the Wells unit. There are also no heat sink fins in the tube to restrict air flow. The sensor does not have a hot wire to get contaminated, so it doesn't require a burn-off phase. However, since the ECM will operate teh burn off circuitry and set a DTC it the process is not completed correctly, Wells installed a load resistor at the burnoff terminal to emulate the load of the hot wire and prevent the ECM from setting an error code. It's a dummy load but gets the job done.



They can be found at any auto parts house that sells Wells/Conrad parts or at World Discounts.

Max,

If you analyze the I.D. of the MAF, especially at the mounting rings for the screens, you'll see that the largest open area is 70mm. The 3" openng at the air filter is equal to 76mm, or 7.07 in². The stock 48mm dual throttle body has a free area of less than 5.6 in² - so where is the restriction? As a matter of fact, even a 52mm TB has less open area than thje stock air cleaner. You don't run into trouble until you get to 58mm, and then only by a little bit. Perforating the bottom of the filter canister and installing a K&N E-0890 element allows for some respectable air flow at consistent rates. Still, any restriction you can improve is a big plus, since the restrictions created tend to be additive in nature.

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Later,
Vader
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"Let the bodies hit the floor!"
Adobe Acrobat Reader

Guest

Actually what I was referring to is that there is only about 3-3.5" of the air filter element itself actually being used at higher RPM's. I have noticed a nice dirty spot on more than a few TA's and other GM's with the same design. I havent actually sat down and calculated it, but I know the stock element, if you are using ALL of it, flows just enough for a typical 350. If you reduce the area of the filter to the amount that is being used in the upper RPM range, I'm sure the CFM would suffer badly. They may as well have shoved the MAF elbow right up against the air filter and eliminated the rest of the filter, because from what I have seen there is little of the filter element being used. I know a 3.5" diameter hole will flow lots of air, but not with a bunch of paper or oiled cotton or foam stuck in it.

drive it

iTrader: (1)

So, is it a code 33 or a 34???? Makes a big diff. on fixin' it! Also your throttle blade adjustment gets more critical as you open up the maf- scan it for an iac count of about 30 at idle and tps volts .54's. If your iac dies you'll set the code 33 every block.(been there, done that.) With more cubic inches I've also had to increase the code 33 parameters-from 45gm/sec to 125gm/sec.-that is easy to do if you burn your own.

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86 406

import_stomper

i have taken the screens out of my maf and never had a problem. I think that maybe the people who have had this problem probably damaged the sensing element or another component in the maf. I don't think it is a problem of air flow or turbulence because even with the screens in the range of air flow and turbulence is very large from idle to wot. i think the removal of the screens wouldn't change either value to a point where it would be out of range of the maf's or computer's stock requirements.

okfoz

I just gotta keep this going..

Here is my thoughts...

Thought 1)
If you have ever been to a water park and slid' down a slide you will remember that you will ride up the sides on EVERY turn. Obviously the water WANTS to go straight BUT the turn forces it to change direction.

The same thing happens in the Turns in an AIR system, more air is forced around the outside of the corner.

Thought 2)
I was watching TV, and they had this flood of water going down this ditch. As it turned out, there was a chain link fence that crossed the ditch and went to the bottom of the ditch, ALL the water had to pass thru the fence. I was watching the water BACK UP behind the fence. REMEMBER these are LARGE 2-3 inch holes that the water is passing through. The water was gushing thruogh the fence but it was smoother once it was on the other side of the fence.

Thought 3)
As for Area, if you have a 3" hole, you will have a flow of "X" the amount of air that can occupy the area of 3" dia is fixed, for this experement. Don't tell me about compression of the air etc etc, I will not comment. The only thing that can change is the velosity that the air is passing through the 3" hole.

The last time I was looking at a screen, I was listening to the wind howel through it it was like a whistling noise. I then looked close at the screen, and I noticed that for every open area, about 10% of that area was screen. Therefore the screen NOT only swirls the air (causes a whistle), it also happens to DECREASE the Area that is available for air to pass through.

WHAT IS MY POINT?
Well, lets consider the following
The Screens do an undesireable thing, 1) it slows the air and creates a dam effect.

On the other hand, Since most of the air coming around the corner will be forced toward the outside of the turn. The screens act like that chainlink fence to smoothe out the air going into the MAF sensor. Therfore the MAF sensor gets a more accurate reading.

Like discussed before, If there was a straight shot into the MAF, the screens would only slow the air. Since there is limited space and area for the ductwork under the hood, this is NOT a possibility, therefore the screens help to stabalize an othewise unstable environment.

Who knows, I might be blowing smoke up my own butt. At this point, I am leaving my screens IN!

Wanna see my sig? look above.

Greg '85 T/A

Jeez Louise!

Scottiewitdabody,

try resetting your computer (as only a couple astute posters mentioned). Disconnect the battery. Turn your key forward for a couple of minutes. Turn the key back to off. Reconnect the battery. Let your ecm re-learn the MAF readings. This is a common part of this mod. If you didn't damage the MAF, you'll be o.k.

What's done is done!

[This message has been edited by Greg '85 T/A (edited June 28, 2001).]

El Guapo

Turn the key forward? What for? The computer will be dead by itself w/in 30 seconds.

Or is there something I dont know?

Clayton

Greg '85 T/A

I read to turn the key forward many years ago. I'm not sure if it helps to discharge the capacitors or what.


***BTW, I can't find anything to support having to turn the key forward - must've read it in Snot Rod or Car Crap.
Just make sure you never disconnect or re-connect the battery with the key forward!***



[This message has been edited by Greg '85 T/A (edited June 29, 2001).]