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De-screen MAF? Yes or No...

This is a discussion on De-screen MAF? Yes or No... within the General Help forums, part of the LSx Technical Help Section category; Well Danzinger, if it makes you feel better, I don't believe in the air straightening theory either. Not sure where ...

  1. #61
    Moderator Firebirdjones's Avatar
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    Well Danzinger, if it makes you feel better, I don't believe in the air straightening theory either. Not sure where that idea came from.
    All that screen does is manage to take up alot of needed space. If you take that screen and crush and compact it into a ball it will give you a good idea just how much space that screen takes up. About 1/3 of the passage way.

    The airflow drastically changes which requires the MAF tables to be reconfigured to compensate. Once that is done it works fine and is known to give HP increases. How much depends on the extent of the engine you are working on. Stockish motors don't see as much, but engines with more bolt on's, camshafts, heads etc....see the most gains.

    I will be doing this experiment with mine soon. After I dial in the A/F ratio with the new headers and make a trip to the track to verify the gains,,,I plan on removing the screen, adjust the MAF tables accordingly and going back to the track to verify any gains. Whether it helps on a stockish motor like mine remains to be seen, but I plan to find out for myself, as the internet discussions can sometimes be skewed with misinformation. I only want to see hard data. I have seen enough dyno runs with screens removed to see that there is something there to be had. But the only way to satisfy myself is to simply do it on my own car and experiment.
    I have started a small log on my car with changes made and ET/MPH with DA recorded for each run so far covering every little change made to the car from front to back. It's interesting some of the things that have worked on the car that the interenet says was a waste of time, and other things that didn't do squat.

  2. #62
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    I haven't de-screened mine, and never will. I think it's pointless.

  3. #63
    Moderator Firebirdjones's Avatar
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    Quote Originally Posted by cavpat View Post
    I haven't de-screened mine, and never will. I think it's pointless.
    Have you even tried it? Are you just saying that because someone told you so? I have seen too many fast cars and many on the dyno with screenless MAF's to ignore it. Those that don't experiment are the ones left behind.

    I have had mine removed in the 97 for ten years, and plan to remove the screen in the 02 SS as well when I get some other testing done.
    After I tune for the screen being removed I will report back with track testing in the near future. If it doesn't do anything for this particular car then I have another MAF with screen waiting to go on the car,,,and maybe try this mod again after the head/cam swap and see if it's worth anything at that point in time. It's all about finding what works best for what you have.

  4. #64
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    The SLP maf comes with the screen and suggests only removing for race applications. It is a GM maf they are selling, just the larger 85mm size. It is still crap and causes lean code faults but it does come with the screen. anybody want one

  5. #65
    Member danziger's Avatar
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    Quote Originally Posted by Firebirdjones View Post
    Well Danzinger, if it makes you feel better, I don't believe in the air straightening theory either. Not sure where that idea came from.
    All that screen does is manage to take up alot of needed space. If you take that screen and crush and compact it into a ball it will give you a good idea just how much space that screen takes up. About 1/3 of the passage way.

    The airflow drastically changes which requires the MAF tables to be reconfigured to compensate. Once that is done it works fine and is known to give HP increases. How much depends on the extent of the engine you are working on. Stockish motors don't see as much, but engines with more bolt on's, camshafts, heads etc....see the most gains.

    I will be doing this experiment with mine soon. After I dial in the A/F ratio with the new headers and make a trip to the track to verify the gains,,,I plan on removing the screen, adjust the MAF tables accordingly and going back to the track to verify any gains. Whether it helps on a stockish motor like mine remains to be seen, but I plan to find out for myself, as the internet discussions can sometimes be skewed with misinformation. I only want to see hard data. I have seen enough dyno runs with screens removed to see that there is something there to be had. But the only way to satisfy myself is to simply do it on my own car and experiment.
    I have started a small log on my car with changes made and ET/MPH with DA recorded for each run so far covering every little change made to the car from front to back. It's interesting some of the things that have worked on the car that the interenet says was a waste of time, and other things that didn't do squat.
    Actually, it does make me feel better that someone else isn't accepting what has so far amounted to speculation as fact. I honestly don't care whether folks remove their screens or not, I'm just trying to present what appears to be an unpopular idea as ungrounded. Heck, if you can show me some definitive proof that removing the MAF screen causes engine issues, I'll gladly eat crow. We may even find that descreened MAFs are dangerous, cause cancer and will often steal food destined to starving kids in Africa.
    The thing is this, the PCM will account for small changes in air-flow, so the removal of the screen should be no problem. "But wait!" you say, "At WOT the system uses set tables unaffected by air-flow." True. But anybody who's seen a stock GM tune knows that is rich on the side of safety, so things should be OK. Besides, we can't be talking THAT MUCH air-flow. The air-straightening thing is another issue that I have a hard time believing as air ducted into the MAF is already coming via straight shot. Anyways, prove me wrong...I'll man up.

  6. #66
    Member jrgswhitels1's Avatar
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    My experience: DE-screening will envelope higher port-velocity, which will encourage better performance!!!!...PERIOD!!!!! Stock programming WILL adjust!!! Leaving screen in WILL slow down port-velocity AND will sample better STOCK tuning for normal driving conditions; that which is NOT favorable to performance, but to fuel mileage and things of that sort!! So, figure out which parameter you want!! SIMPLE and EASY!!! Ever had your MAF tested for flow? YOU WILL FREAK, just how much the screen really disrupts flow! Heck, I couldnt believe it! I even tested the screen by blowing into it, with your hand 1" behind it! At that same rate, move the screen out of the way? SURPRISED??!!!!

  7. #67
    Moderator Firebirdjones's Avatar
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    Quote Originally Posted by SSTODD View Post
    The SLP maf comes with the screen and suggests only removing for race applications. It is a GM maf they are selling, just the larger 85mm size. It is still crap and causes lean code faults but it does come with the screen. anybody want one
    Ya if you take that screen out of it first

  8. #68
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    Quote Originally Posted by jrgswhitels1 View Post
    My experience: DE-screening will envelope higher port-velocity, which will encourage better performance!!!!...PERIOD!!!!! Stock programming WILL adjust!!! Leaving screen in WILL slow down port-velocity AND will sample better STOCK tuning for normal driving conditions; that which is NOT favorable to performance, but to fuel mileage and things of that sort!! So, figure out which parameter you want!! SIMPLE and EASY!!! Ever had your MAF tested for flow? YOU WILL FREAK, just how much the screen really disrupts flow! Heck, I couldnt believe it! I even tested the screen by blowing into it, with your hand 1" behind it! At that same rate, move the screen out of the way? SURPRISED??!!!!
    Agreed on the idea that it reduced airflow-no question. How are you certain the MAF will adjust to a descreened MAF? Have you Dynoed the car without the screen to prove any gains that make it a worthey mod?
    Not doubting you but I am just curious.

  9. #69
    Moderator Firebirdjones's Avatar
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    Quote Originally Posted by BREAKxNECKxSPEED View Post
    Agreed on the idea that it reduced airflow-no question. How are you certain the MAF will adjust to a descreened MAF? Have you Dynoed the car without the screen to prove any gains that make it a worthey mod?
    Not doubting you but I am just curious.
    Thats exactly what I plan to do,,,only I plan to make the required adjustments in the MAF tables after screen removal with HPtuners, and see what happens for myself.

  10. #70
    Member jrgswhitels1's Avatar
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    As a matter of fact,No and Yes!! Personally no!, I havent tried to dyno with/without screen but my local tuner (Mike Norris of Norris Motorsports)has and told me while tuning one of my cars, is that there are too many variables to prove it consistent! However, he agree's that the screen yields good emissions and mileage, but not usually recommended for many high-performance applications. GM's MAF can easily adjust to fuel enrichments as quickly as it can sample out port speed vs port displacement! Its not relative to say,however that, descreening will not conservatively reduce power output! What is concernable is whats directly before the MAF and the net effect of rate-of-air sampled versus volume of air, both of which can directly impact power! So, my money is on de-screening for MAX power!... but, to each their own, right?

  11. #71
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    I would believe Mike Norris-from what I hear that guy knows whats going on for sure.
    I was just curious if any dyno proven gains were reported and how much of a gain. I personally am not one of those people who does things like throttle body bypass etc. I realize every HP counts but things like that gain so little (if any) so why even fool with it. Thats just me though. I mean its kinda like turning your ac off-which I am not gonna do either LOL.

  12. #72
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    I descreened mine, but I have HPTuners. I dialed in the spark and fuel until no KR shows at all... Descreening the MAF can have a leaning effect, as air can slip past the MAF unnoticed, but unless you're tuned or have a power adder you don't have anything to fear, these cars come with like an 11.8/1 AFR from the factory and the reason people notice gains associated with this mod is that any leaning condition that does occur is well within the limits of safety--it just makes more power. Now as to the straight shot, that is a good point as well. I only noticed KR on pulls I did from a roll, and only intermittently then. Things that dramatically change your airflow pattern on the fly seem to affect the post-!screen maf adversely but from a dig or after the initial shock of the dramatic increase of airflow your maf will read correctly again. BTW I removed mine in order to spray a dry hit of nitrous (which I will do eventually, after I have a baseline N/A track time that isn't fast enough :P) and if you plan on spraying dry, removing the screen at least prior to spraying is a MUST!!!! There have been cases where the screen buckled under the pressure of all the nitrous and was run thru the engine... fortunately, I don't know of anything that this has destroyed or broken, but you get the point. It's a risk to have it in there if you're spraying.

  13. #73
    Member danziger's Avatar
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    Quote Originally Posted by jrgswhitels1 View Post
    As a matter of fact,No and Yes!! Personally no!, I havent tried to dyno with/without screen but my local tuner (Mike Norris of Norris Motorsports)has and told me while tuning one of my cars, is that there are too many variables to prove it consistent! However, he agree's that the screen yields good emissions and mileage, but not usually recommended for many high-performance applications. GM's MAF can easily adjust to fuel enrichments as quickly as it can sample out port speed vs port displacement! Its not relative to say,however that, descreening will not conservatively reduce power output! What is concernable is whats directly before the MAF and the net effect of rate-of-air sampled versus volume of air, both of which can directly impact power! So, my money is on de-screening for MAX power!... but, to each their own, right?
    Actually, Mike Norris tuned my Z28 after the H/C/N install. The descreened MAF was a non-issue. Mike is definitely a good guy and one to stand behind his work.

  14. #74
    Member danziger's Avatar
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    Quote Originally Posted by richard head View Post
    Descreening the MAF can have a leaning effect, as air can slip past the MAF unnoticed
    Again, not trying to be an ass, but how does air "slip past" because the screen is gone?

  15. #75
    Grand Imperial Wizard Sarge's Avatar
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    My buddy Third Degree nails it for you.......


    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 are.....by 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 turbulence 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 congratulations 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? .....you should be on Speed Density with a custom tune."

    And there you have it.......

  16. #76
    Moderator Firebirdjones's Avatar
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    Still not convinced. Too many tuners doing it and making power. Your last paragraph contradicts itself. Praising how well the MAF works for different weather conditions yet saying speed density is the way to go for power.

    I have seen many MAF setups making just as much power, and still retain the ability to adjust to DA changes on the fly.

    I don't believe there is a resolution to this discussion, as it's a matter of opinion really. Some like to do it and some don't, while others like to eliminate the MAF all together.

    I am either way on it really. But removing my screen soon and retuning with HPtuner to find out for myself will finally help me decide what really works. I will be going back and forth with/without the screen with various setups on the car, and find at what point the screen removal helps, if any at all.

  17. #77
    Grand Imperial Wizard Sarge's Avatar
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    No it says if your highly modified SD is the way to go. If your stock or have a few bolt ons leave the thing alone as your not gaining anything. And for the record tuners also are victrims of internet rumors themselves. They are not immune.

  18. #78
    Member danziger's Avatar
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    Sarge- That is an interesting viewpoint and re-hashes many of the arguments already made. The question is still one of turbulence vs. restriction. Laminar airflow is a great theory, and one that I would be willing to accept with some evidence behind it. However, his postulations about air getting by unmeasured make no sense as the screen doesn't channel air like a funnel to the sensor. Air going by at the bottom of the orfice versus closer to the center will be the same, screened or not. The ported MAF is another topic altogether... Thank you for posting something informative and constructively adding to the discussion.
    2000 Z28 382/nitrous...sold and missed.
    2004 Z06 CE Z16...still looks stock.

  19. #79
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    "air getting by" the maf doesnt make sense to me. Like stated above-even with the screen there has to be plenty of air getting by anyways. BUT thats a great explanation of how the maf works and for me and my stock motor(with a couple of small mods) I think leaving the screen in is the thing to do.

  20. #80
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    Seems like it makes sense to leave it in unless you're getting a dyno tune.
    Vote for Pedro.

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