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descreening the MAF questions

10596 Views 11 Replies 11 Participants Last post by  OKLAGMCRUISER
ok i always hear about descreening your MAF for alittle better performance and gas mileage , i have an 01 sierra ext cab short bed with 5.3 4wd with a k&n fipk in it , can anyone help me out with this i have some time on my hands and want to do it any help would be appreciated thanks guys
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· 03 Tahoe
1,967 Posts
Well, in my experiences it's not worth it. It can increase mileage minimally and usually no seat of the pants feel. The issues w/ doing it are that the airflow isn't even across the sensor which can cause the engine to go lean since the computer isn't registering all the air going in, only anything over the sensor, and can lead to less fuel being injected.

It's a freebie mod that really doesn't do much. I honestly wouldn't do it.


· Registered
17 Posts
some are for it, some arent. i did mine. doing it is easy, you just pull the mass airflow sensor out(its on the intake tube) and grab a screwdriver and pop the screen out, being careful not to damage the actual sensor itself

47,204 Posts
Don't do it, it's not the best thing to do. It's free...that should tell ya the quality of the mod. It throws the A/F ratio off and makes it harder to tune around.

· I am the Moderatonator!
1,671 Posts
blwclvl said:
you will notice more if you do that coupled with an open air intake system. That is pretty much all the granatelli maf is. The best bang for your buck I still feel is the hypertech reprogrammer
The only thing a descreened stock MAF has in common with the granatelli is they both have no screens. The Granatelli unit is tuned to take advantage of being open. When you descreen the stocker, you are allowing lots of unmetered air enter your engine. I made the mistake of descreening my stocker, and it made me run really lean. That free mod ended up costing me $50 for a new MAF sensor.

This FREE MOD does about as much as the TB bypass.

· Registered
25 Posts
Re: descreening the MAF questions part 1

I think this came from the LS1 site:

Tech Tips
MAF Screen Removal
One Word ~ DON'T

Let me start by saying this article is a combination of research available on the internet, my humble opinion, and the following of hundreds of tech post regarding MAF Screen Removal.

A few years ago Hot Rod Magazine ran an article on the proposed horsepower gain that could be had for free by the removal of the front and rear MAF Screens. Adding to the resulting screen removal frenzy are companies like TPIS that offer the service of removing the screens and "gutting" the fins, again, for a reported HP gain.

The most critical note to be realized (that most don't) is that the engines that these were being used on were heavily modified.

The Myth: Across the internet and word of mouth spread the news of this "free mod" and countless pages promoted the technique of MAF Screen Removal without considering some very basic theories and the potential harm of doing this mod. Consequently time after time you will see the post and topics "I removed my screens - now Code 33".

The Fact: The MAF Screen Removal Process WILL NOT CREATE horsepower within itself. It can only in the right conditions FREE UP horsepower that ALREADY EXIST and only under certain conditions.
1. Your stock MAF with screens will outflow your stock 48mm throttle body.
2. It will even outflow a 52mm throttle body.
3. It will also outflow your stock intake.

This Means: that if you are still using these stock components your MAF screen removal process is totally wasted and potentially (code 33) dangerous and could cost $100.00 + if you screw it up. The MAF has to be the most restrictive element in your chain of flow to even possibly make the mod worth anything and ONLY if you already have the horsepower to free up by a modified throttle body and intake.

Why the Screens?

What kicks me in the pants is not only do I personally feel that these screens are the single most important part of the MAF but that they serve multiple purposes. The screen in the front filters potential debris, prevents something from being dropped into the MAF when working on car, a tool slipping, etc., and the rear screen not only serves the same protective service but it also helps cushion potential damages to the fragile MAF wire that can be caused by a backfire under lean conditions. And these services are secondary to their primary purpose which is to regulate airflow for measuring purposes.

Are the Screens Restrictive?

Absolutely they are, but by design. Is your voltage regulator restrictive? Is your air cleaner restrictive? Is your fuel filter restrictive? Are your fuel injectors restrictive? Is your fuel pressure regulator restrictive? Yes they design. Would you remove your air cleaner or fuel filter? We are blessed with the common sense that although restrictive we find these components necessary for proper operation and to remove them would be foolish or asking for trouble. It is very unfortunate that we don't possess the same common sense regarding the MAF sensor.

Theory of Operation

Understand two terms first of all. Turbulent Airflow and Laminar Airflow. They are opposites. Without definition we can identify with "turbulent" but "laminar" airflow would define as "smooth, straightened out, regulated".

To help understand some conflicting articles I will point out an important factor here right away. There is no such thing as turbulence free airflow. Airflow is a "fluid flow" and a fluid flowing past obstructions, against boundaries, even the composition of the fluid itself in different densities and pressures create turbulences that can't be removed. So when we speak of Laminar Airflow being smoothed out and being the opposite of turbulent airflow we're speaking of a "controlled turbulence" vs. "uncontrolled turbulence".

Envision this process by thinking of your kitchen faucet. The little screen on the end. Take it out and watch your water flow increase but also notice it splash around and surge. You can see the uneven flow very easily. Put the aerator back in and see it smooth out in a more regulated even flow. Look at the end of most hair dryers and they will have a screen in them. Of course this is to prevent getting your hair sucked up in there and catching your head on fire BUT it also disperses the air in a more even, regulated pattern. Think of the construction of a dam on a river. You KNOW it is restrictive. It "holds back" the natural flow of water and regulates it to a desired given amount. Why? To do something productive with the process of flow. Just like your MAF screens.

The MAF Process

I am going to chop this section down to the most basic of processes. GM didn't invent this process, as a matter of fact it is the same process used by the weather industry to measure "chill factor" so it's theory was utilized by GM not invented by them.

1. You have a small wire inside your MAF which can be heated.
2. It is calibrated at zero airflow to be a certain temperature.
3. Air flowing across the wire cools it off. The more air flow the cooler the wire.
4. A voltage is supplied to that wire to keep it at a constant temperature. The more air flowing, the cooler the wire, the more voltage required to keep it the same temp.
5. This voltage fluctuation is a measurable, readable function which when converted to a digital output can be used for calibrations of airflow entering your intake.
6. These calibrations are referenced to a lookup table stored in your ECM and based on these fluctuations various functions of your engine are controlled based on the amount of airflow you are encountering.

The screens are there simply to provide a steady, stable, regulated environment for the most precise calculations available.

Now I will point you back to one of my previous "goofy-assed" examples and ask: Would it be easier to count the number of gallons that flow past a certain point in the river ...with the dam or without it? That is what your screens are for... to establish "near as possible" level playing field ground zero reference point for calibrations.

What Happens When They are Removed

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. Lower frequency outputs are being read by the lookup charts and the calculations are based on 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.

In Summary I would say that I have heard of people making this mod and not having trouble codes. I have also heard of reported gains in performance. In both of these situations, if true, you have my respect and congradulations. But I have never seen proof of these gains especially on a stock setup. I have however lost count of the number of post that are encountering trouble after making this "free" mod. Further I would say that if the horsepower is not there in the first place your sure not going to create any new horsepower cutting out your screens.

The MAF is a truly unique and awesome device that allows us to drive in different environments (altitudes) with no intake modifications. Allows us to make "other" performance mods without having to calibrate a new PROM. To butcher it and make it less accurate and precise just doesn't make sense to me.

1. If you are driving a stock intake car this mod will do absolutely nothing for you.
2. If you have such a heavily modified engine that it would make a difference Why are you using the MAF system anyway? should be on Speed Density with a custom chip.

My personal disclaimer is this. If you have already cut your screens out I am not saying your stupid or you did something bad. I am saying that maybe you were misinformed or that there was a lack of information available to make the best possible decision for your situation. This article is not to point out mistakes, make fun of, or even say "I'm right ~ you're wrong". But merely to present an opposing view, a difference of opinion, and possibly a closer understanding of a mysterious, complex component.

MAF Screen Removal

The Mass Air Flow (MAF) Sensor is located between the air filter assembly and the intake Bellows, and it's name implies it's function. It measures the amount (mass) of air entering the engine during operation, and uses this information to (in part) determine the correct air/fuel mixture for the conditions.
The MAF is an excellent sensor in that it has the ability to measure four different characteristics of the incoming air simultaneously: temperature, pressure, volume, and humidity. This ability give the fuel management system remarkable flexibility and adaptability. One drawback, however is the MAF represents a significant restriction to air flow into the engine. In stock trim the MAF can flow around 529 cfm maximum - OK for stock applications, but not if any modifications are performed.
The major restriction is the "debris screen". It is meant to protect the delicate heated wire, but to you its purpose is to keep your car from GOING FASTER.
Fortunately, there is a relatively simple modification that can be done to net larger gains in air flow - up to 180 cfm in most cases, and usually more.
Before we begin, see the CMA statement again: located on the main mods page.
Part 2 in second post

· Registered
25 Posts
Part 2

First unplug the MAF, and remove it from the car. Place the sensor on a firm, flat surface. You will notice that the screen is held in with a metal or plastic ring that is glued or fitted into a bore (grove) on the wall of the MAF housing. Using a sharp tool of some type (small knife or screwdriver) work under the ring until you can wedge the tool between the ring and the bore. Take your time - it is very easy to slip and damage something. Then, work your way around the ring, carefully prying it away. The metal ring will just pop out and the plastic one may crack. At this point you will know you've won this round.Next, use the tool to work the screen out in a way similar to the ring. This shouldn't be difficult. Simple, eh? You can use the tool to carefully remove any pieces of the plastic ring or glue that might be left stuck in the MAF.
Some OE MAFs may have two screens, so do the same procedure on both ends. Some after market MAF units have only one screen.
You've just gained about 180 cfm in about 10 minutes or less. And most of that time will be spent putting the air box back together.
No noticeable power gain was detected. But there was a slight increase in exhaust tone at ideal and throttle and I seem to be getting better gas mileage.

Not telling you not to do it, but others have tried it.

· Loves yoga pants
3,842 Posts
I know someone that has one that is already descreened that you can purchase for 75 bucks shipped. That way if you don't like it you have yours to put back into the truck. Let me know. That price is what he paid for it.
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