descreening maf
Registered User
Joined: Feb 2004
Posts: 4,800
Re: descreening maf
Originally Posted by Z28SORR
Every time this subject comes up the same people respond with the same statements, and without any appearent scientific knowege or any real understanding of what is going on. They all seem to be just repeating what someone else has said or what they've heard somewhere. So lets look at this objectively and with a mind on the science behind it all.
Someone said that the sceen is there to reduce the incoming air turbulence. The screen I removed from my MAF was a round wire mesh screen. And any aerodynamicist will tell you the last thing you would use to reduce turbulance is a round wire. The only shape that creates more turbulance than a round wire is a flat plate. If you wanted to reduce the turbulance, a very thin vane or vanes would work far better . And in fact I have seen some of these with honeycomb foil screens, which on the surface would lend credence to this idea. However you have to ask yourself, "how much turbulance are we really talking about". The air flow into this meter is though a smooth tube with the only turbulance creating parts(the rubber bellows) after the meter, except for the screen of course. Another person said that it's there to evenly distribute the air flow. Well the screen with all the turbulence it creates would certainly accomplish that goal, if it were required. But again if you look at the system, where you have air being pulled through a smooth 4 or 5 inch tube at 3 to 6 hundred cfm. To be uneven the mass of air would have to be higher on one side of the tube compared to the other side. I doubt that this would be a demonstratable problem. So unless y'all can come up with something better than this, I'll continue to believe the screen is there to protect a very thin and delecate wire from some foriegn object damage.
The other camp, saids it will destroy the calibration or the computer will relearn and readjust for the extra flow. This meter simply reads the mass of the air that crosses the wire. The calibration is set by producing a set voltage for a set cfm. So how would increasing the amount of flow in any way harm the meter. It doesn't "care" if there is a screen in front of the wire or not. As for the computer its job is to maintain a set A/F mix across a set of parameters. By saying that it relearns, your really saying that it somehow knows THIS increase does not require a corresponding increase in fuel to maintain the correct A/F mix. So it is reducing the power, as if it's job was to keep the engine at a specific HP level no matter what mods where done to it. I think you can see the absurdity in this idea if we carry it out to it's logical conclusion.
The fact is that any increase in air flow has to garner and equal increase in power, within the system abilities to measure it, which this is.
I believe the problem is simply that this is just to small a difference to be observable. And that because the meter is so delecate many people damage it and so end up with a negative result.
Someone said that the sceen is there to reduce the incoming air turbulence. The screen I removed from my MAF was a round wire mesh screen. And any aerodynamicist will tell you the last thing you would use to reduce turbulance is a round wire. The only shape that creates more turbulance than a round wire is a flat plate. If you wanted to reduce the turbulance, a very thin vane or vanes would work far better . And in fact I have seen some of these with honeycomb foil screens, which on the surface would lend credence to this idea. However you have to ask yourself, "how much turbulance are we really talking about". The air flow into this meter is though a smooth tube with the only turbulance creating parts(the rubber bellows) after the meter, except for the screen of course. Another person said that it's there to evenly distribute the air flow. Well the screen with all the turbulence it creates would certainly accomplish that goal, if it were required. But again if you look at the system, where you have air being pulled through a smooth 4 or 5 inch tube at 3 to 6 hundred cfm. To be uneven the mass of air would have to be higher on one side of the tube compared to the other side. I doubt that this would be a demonstratable problem. So unless y'all can come up with something better than this, I'll continue to believe the screen is there to protect a very thin and delecate wire from some foriegn object damage.
The other camp, saids it will destroy the calibration or the computer will relearn and readjust for the extra flow. This meter simply reads the mass of the air that crosses the wire. The calibration is set by producing a set voltage for a set cfm. So how would increasing the amount of flow in any way harm the meter. It doesn't "care" if there is a screen in front of the wire or not. As for the computer its job is to maintain a set A/F mix across a set of parameters. By saying that it relearns, your really saying that it somehow knows THIS increase does not require a corresponding increase in fuel to maintain the correct A/F mix. So it is reducing the power, as if it's job was to keep the engine at a specific HP level no matter what mods where done to it. I think you can see the absurdity in this idea if we carry it out to it's logical conclusion.
The fact is that any increase in air flow has to garner and equal increase in power, within the system abilities to measure it, which this is.
I believe the problem is simply that this is just to small a difference to be observable. And that because the meter is so delecate many people damage it and so end up with a negative result.
.
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Joined: May 2004
Posts: 1,754
Re: descreening maf
if i was able to start over, i wouldn't have taken my screen out. i took it out over 2 years ago when I first got my car. if after my h/c im seeing problems with my MAP #'s, I may sell it and buy another stocker.
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Joined: Aug 2002
Posts: 2,325
From: BC
Re: descreening maf
Originally Posted by Z28SORR
Every time this subject comes up the same people respond with the same statements, and without any appearent scientific knowege or any real understanding of what is going on. They all seem to be just repeating what someone else has said or what they've heard somewhere. So lets look at this objectively and with a mind on the science behind it all.
Someone said that the sceen is there to reduce the incoming air turbulence. The screen I removed from my MAF was a round wire mesh screen. And any aerodynamicist will tell you the last thing you would use to reduce turbulance is a round wire. The only shape that creates more turbulance than a round wire is a flat plate. If you wanted to reduce the turbulance, a very thin vane or vanes would work far better. And in fact I have seen some of these with honeycomb foil screens, which on the surface would lend credence to this idea. However you have to ask yourself, "how much turbulance are we really talking about". The air flow into this meter is though a smooth tube with the only turbulance creating parts(the rubber bellows) after the meter, except for the screen of course. Another person said that it's there to evenly distribute the air flow. Well the screen with all the turbulence it creates would certainly accomplish that goal, if it were required. But again if you look at the system, where you have air being pulled through a smooth 4 or 5 inch tube at 3 to 6 hundred cfm. To be uneven the mass of air would have to be higher on one side of the tube compared to the other side. I doubt that this would be a demonstratable problem. So unless y'all can come up with something better than this, I'll continue to believe the screen is there to protect a very thin and delecate wire from some foriegn object damage.
The other camp, saids it will destroy the calibration or the computer will relearn and readjust for the extra flow. This meter simply reads the mass of the air that crosses the wire. The calibration is set by producing a set voltage for a set cfm. So how would increasing the amount of flow in any way harm the meter. It doesn't "care" if there is a screen in front of the wire or not. As for the computer its job is to maintain a set A/F mix across a set of parameters. By saying that it relearns, your really saying that it somehow knows THIS increase does not require a corresponding increase in fuel to maintain the correct A/F mix. So it is reducing the power, as if it's job was to keep the engine at a specific HP level no matter what mods where done to it. I think you can see the absurdity in this idea if we carry it out to it's logical conclusion.
The fact is that any increase in air flow has to garner and equal increase in power, within the system abilities to measure it, which this is.
I believe the problem is simply that this is just to small a difference to be observable. And that because the meter is so delecate many people damage it and so end up with a negative result.
Someone said that the sceen is there to reduce the incoming air turbulence. The screen I removed from my MAF was a round wire mesh screen. And any aerodynamicist will tell you the last thing you would use to reduce turbulance is a round wire. The only shape that creates more turbulance than a round wire is a flat plate. If you wanted to reduce the turbulance, a very thin vane or vanes would work far better. And in fact I have seen some of these with honeycomb foil screens, which on the surface would lend credence to this idea. However you have to ask yourself, "how much turbulance are we really talking about". The air flow into this meter is though a smooth tube with the only turbulance creating parts(the rubber bellows) after the meter, except for the screen of course. Another person said that it's there to evenly distribute the air flow. Well the screen with all the turbulence it creates would certainly accomplish that goal, if it were required. But again if you look at the system, where you have air being pulled through a smooth 4 or 5 inch tube at 3 to 6 hundred cfm. To be uneven the mass of air would have to be higher on one side of the tube compared to the other side. I doubt that this would be a demonstratable problem. So unless y'all can come up with something better than this, I'll continue to believe the screen is there to protect a very thin and delecate wire from some foriegn object damage.
The other camp, saids it will destroy the calibration or the computer will relearn and readjust for the extra flow. This meter simply reads the mass of the air that crosses the wire. The calibration is set by producing a set voltage for a set cfm. So how would increasing the amount of flow in any way harm the meter. It doesn't "care" if there is a screen in front of the wire or not. As for the computer its job is to maintain a set A/F mix across a set of parameters. By saying that it relearns, your really saying that it somehow knows THIS increase does not require a corresponding increase in fuel to maintain the correct A/F mix. So it is reducing the power, as if it's job was to keep the engine at a specific HP level no matter what mods where done to it. I think you can see the absurdity in this idea if we carry it out to it's logical conclusion.
The fact is that any increase in air flow has to garner and equal increase in power, within the system abilities to measure it, which this is.
I believe the problem is simply that this is just to small a difference to be observable. And that because the meter is so delecate many people damage it and so end up with a negative result.
There are many people on the board with descreened maf whom have had problems. There are probably more who think they're "ok" but have never hooked up a scanner to see if the engines running slightly more lean or rich in certain cells.
There are some who have no problems at all since the flow of air was straight enough.
It's not worth taking out for a possible few hp and a very likely chance other issues may develop.
Registered User
Joined: Sep 2003
Posts: 376
From: VA
Re: descreening maf
Originally Posted by Z28SORR
Every time this subject comes up the same people respond with the same statements, and without any appearent scientific knowege or any real understanding of what is going on. They all seem to be just repeating what someone else has said or what they've heard somewhere. So lets look at this objectively and with a mind on the science behind it all.
Someone said that the sceen is there to reduce the incoming air turbulence. The screen I removed from my MAF was a round wire mesh screen. And any aerodynamicist will tell you the last thing you would use to reduce turbulance is a round wire. The only shape that creates more turbulance than a round wire is a flat plate. If you wanted to reduce the turbulance, a very thin vane or vanes would work far better. And in fact I have seen some of these with honeycomb foil screens, which on the surface would lend credence to this idea. However you have to ask yourself, "how much turbulance are we really talking about". The air flow into this meter is though a smooth tube with the only turbulance creating parts(the rubber bellows) after the meter, except for the screen of course. Another person said that it's there to evenly distribute the air flow. Well the screen with all the turbulence it creates would certainly accomplish that goal, if it were required. But again if you look at the system, where you have air being pulled through a smooth 4 or 5 inch tube at 3 to 6 hundred cfm. To be uneven the mass of air would have to be higher on one side of the tube compared to the other side. I doubt that this would be a demonstratable problem. So unless y'all can come up with something better than this, I'll continue to believe the screen is there to protect a very thin and delecate wire from some foriegn object damage.
The other camp, saids it will destroy the calibration or the computer will relearn and readjust for the extra flow. This meter simply reads the mass of the air that crosses the wire. The calibration is set by producing a set voltage for a set cfm. So how would increasing the amount of flow in any way harm the meter. It doesn't "care" if there is a screen in front of the wire or not. As for the computer its job is to maintain a set A/F mix across a set of parameters. By saying that it relearns, your really saying that it somehow knows THIS increase does not require a corresponding increase in fuel to maintain the correct A/F mix. So it is reducing the power, as if it's job was to keep the engine at a specific HP level no matter what mods where done to it. I think you can see the absurdity in this idea if we carry it out to it's logical conclusion.
The fact is that any increase in air flow has to garner and equal increase in power, within the system abilities to measure it, which this is.
I believe the problem is simply that this is just to small a difference to be observable. And that because the meter is so delecate many people damage it and so end up with a negative result.
Someone said that the sceen is there to reduce the incoming air turbulence. The screen I removed from my MAF was a round wire mesh screen. And any aerodynamicist will tell you the last thing you would use to reduce turbulance is a round wire. The only shape that creates more turbulance than a round wire is a flat plate. If you wanted to reduce the turbulance, a very thin vane or vanes would work far better. And in fact I have seen some of these with honeycomb foil screens, which on the surface would lend credence to this idea. However you have to ask yourself, "how much turbulance are we really talking about". The air flow into this meter is though a smooth tube with the only turbulance creating parts(the rubber bellows) after the meter, except for the screen of course. Another person said that it's there to evenly distribute the air flow. Well the screen with all the turbulence it creates would certainly accomplish that goal, if it were required. But again if you look at the system, where you have air being pulled through a smooth 4 or 5 inch tube at 3 to 6 hundred cfm. To be uneven the mass of air would have to be higher on one side of the tube compared to the other side. I doubt that this would be a demonstratable problem. So unless y'all can come up with something better than this, I'll continue to believe the screen is there to protect a very thin and delecate wire from some foriegn object damage.
The other camp, saids it will destroy the calibration or the computer will relearn and readjust for the extra flow. This meter simply reads the mass of the air that crosses the wire. The calibration is set by producing a set voltage for a set cfm. So how would increasing the amount of flow in any way harm the meter. It doesn't "care" if there is a screen in front of the wire or not. As for the computer its job is to maintain a set A/F mix across a set of parameters. By saying that it relearns, your really saying that it somehow knows THIS increase does not require a corresponding increase in fuel to maintain the correct A/F mix. So it is reducing the power, as if it's job was to keep the engine at a specific HP level no matter what mods where done to it. I think you can see the absurdity in this idea if we carry it out to it's logical conclusion.
The fact is that any increase in air flow has to garner and equal increase in power, within the system abilities to measure it, which this is.
I believe the problem is simply that this is just to small a difference to be observable. And that because the meter is so delecate many people damage it and so end up with a negative result.
Last edited by SnakeSkinner28; Dec 7, 2004 at 08:52 PM.
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Joined: Mar 2003
Posts: 125
From: Wilmington, Delaware
Re: descreening maf
Wow... you guys are getting pretty deep on this subject.
I removed my screens 30K miles ago, cut the bridge out and put the housing on the lathe to open the bore size and polish the interior of the housing. By doing this I have reduced the air velocity across the wire which by the computer's programming it "sees" less air by its own accord. The truth is that more airflow can get to the engine with less restriction in the intake and thus I have leaned out my overly rich fuel mixture. My throttle response is much improved, no SES lights and my overall economy is better. I can also feel a greater acceleration.
Now, I can get into all sorts of quantitative dynamics of air, density and pressures... but I do that for a living with aircraft and hate to work while at home.
I removed my screens 30K miles ago, cut the bridge out and put the housing on the lathe to open the bore size and polish the interior of the housing. By doing this I have reduced the air velocity across the wire which by the computer's programming it "sees" less air by its own accord. The truth is that more airflow can get to the engine with less restriction in the intake and thus I have leaned out my overly rich fuel mixture. My throttle response is much improved, no SES lights and my overall economy is better. I can also feel a greater acceleration.
Now, I can get into all sorts of quantitative dynamics of air, density and pressures... but I do that for a living with aircraft and hate to work while at home.
Registered User
Joined: Sep 2003
Posts: 376
From: VA
Re: descreening maf
Originally Posted by David A. Wilks
Wow... you guys are getting pretty deep on this subject.
I removed my screens 30K miles ago, cut the bridge out and put the housing on the lathe to open the bore size and polish the interior of the housing. By doing this I have reduced the air velocity across the wire which by the computer's programming it "sees" less air by its own accord. The truth is that more airflow can get to the engine with less restriction in the intake and thus I have leaned out my overly rich fuel mixture. My throttle response is much improved, no SES lights and my overall economy is better. I can also feel a greater acceleration.
Now, I can get into all sorts of quantitative dynamics of air, density and pressures... but I do that for a living with aircraft and hate to work while at home.
I removed my screens 30K miles ago, cut the bridge out and put the housing on the lathe to open the bore size and polish the interior of the housing. By doing this I have reduced the air velocity across the wire which by the computer's programming it "sees" less air by its own accord. The truth is that more airflow can get to the engine with less restriction in the intake and thus I have leaned out my overly rich fuel mixture. My throttle response is much improved, no SES lights and my overall economy is better. I can also feel a greater acceleration.
Now, I can get into all sorts of quantitative dynamics of air, density and pressures... but I do that for a living with aircraft and hate to work while at home.
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Joined: Nov 2000
Posts: 1,937
From: Ft. Worth, TX
Re: descreening maf
If you want to flow more air without the MAF seeing it to lean out the mixture and produce more power since it is overly rich from the factory, why not just reprogram the computer to do that which will be accurrate rather than porting and polishing and boring out the MAF and guessing at how much air its really flowing
There's several fueling tables and target AF ratio tables that can easily be manipulated to produce a leaner mixture and will do it accurately. The BLMs are used by the computer (its learning factor) to adjust fuel to get to the target AF ratio in the tables. If you go porting the MAF to give it a false lower air reading than its really getting, your BLMs are going to be wacked out, possibly to the extent that they are maxxed on the lean side and having no control over fueling.
Other ways to lean out mixture:
1)Cut a hole in the intake tract between TB and MAF. Filter optional since that may restrict airflow.
2) Reduce fuel pressure if you have an adjustable regulator.
3) Crip fuel supply line to limit fuel volume.
4) Unplug some vac lines after the TB.
But all of these are uncontrolled variables but are ways to lean it out without touching the computer tables, but no ones doing these things so why jack with the MAF?
There's several fueling tables and target AF ratio tables that can easily be manipulated to produce a leaner mixture and will do it accurately. The BLMs are used by the computer (its learning factor) to adjust fuel to get to the target AF ratio in the tables. If you go porting the MAF to give it a false lower air reading than its really getting, your BLMs are going to be wacked out, possibly to the extent that they are maxxed on the lean side and having no control over fueling.
Other ways to lean out mixture:
1)Cut a hole in the intake tract between TB and MAF. Filter optional since that may restrict airflow.
2) Reduce fuel pressure if you have an adjustable regulator.
3) Crip fuel supply line to limit fuel volume.
4) Unplug some vac lines after the TB.
But all of these are uncontrolled variables but are ways to lean it out without touching the computer tables, but no ones doing these things so why jack with the MAF?
Last edited by 2QUIK6; Dec 8, 2004 at 09:31 AM.
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Joined: Jul 2002
Posts: 3,768
From: Friendswood, TX, USA
Re: descreening maf
Ok, now you've gone and done it! Y'all went and hurt my feelings.
It was not my intent to go into the specifics of how the MAF works but only to discuss the air flow though it! Which I still maintain is relatively turbulent free. Which is why many of the after market MAF are screen free.
I've added a short para. on it's function and a related CarCraft article. You'll note that under the picts of the MAF it says, "GM ’94-and-up MAF units aren’t a major restriction through 400 hp, but Morgan Motorsports sees gains even on stockers by going to a larger meter ID. Options include removing the GM unit’s (left) screen and dividing fin, then porting it out (center), or installing a larger aftermarket unit (right)." (from CARCRAFT Mag.) I guess i'm not the only one thats wrong.
Mass Air Flow Sensor (MAF) - The mass air flow sensor is positioned in the air intake duct or manifold and measures the mass of incoming air. From this acquired data the ECU calculates the required fuel for the specific air mass flow rate. The MAF works on the hot wire or hot film concept. The hot wire/film is maintained at a constant calibrated temperature. The passing air cools down the hot wire/film and the added energy required to maintain the calibrated temperature is directly proportional to the mass of air passing by the hot wire. The MAF also compensates for humidity as humid, denser or cooler air, absorbs more heat from the sensor, requiring more current to maintain the calibration temperature.
http://www.carcraft.com/techarticles/24549/
P.S. I'll freely admit that I may not have been as precise with my terms as I should have been, but I was writing quickly. Interesting that all you experts that were so quick to jump in my ****, didn't put out any effort to answer the question in any detail.
It was not my intent to go into the specifics of how the MAF works but only to discuss the air flow though it! Which I still maintain is relatively turbulent free. Which is why many of the after market MAF are screen free.
I've added a short para. on it's function and a related CarCraft article. You'll note that under the picts of the MAF it says, "GM ’94-and-up MAF units aren’t a major restriction through 400 hp, but Morgan Motorsports sees gains even on stockers by going to a larger meter ID. Options include removing the GM unit’s (left) screen and dividing fin, then porting it out (center), or installing a larger aftermarket unit (right)." (from CARCRAFT Mag.) I guess i'm not the only one thats wrong.
Mass Air Flow Sensor (MAF) - The mass air flow sensor is positioned in the air intake duct or manifold and measures the mass of incoming air. From this acquired data the ECU calculates the required fuel for the specific air mass flow rate. The MAF works on the hot wire or hot film concept. The hot wire/film is maintained at a constant calibrated temperature. The passing air cools down the hot wire/film and the added energy required to maintain the calibrated temperature is directly proportional to the mass of air passing by the hot wire. The MAF also compensates for humidity as humid, denser or cooler air, absorbs more heat from the sensor, requiring more current to maintain the calibration temperature.
http://www.carcraft.com/techarticles/24549/
P.S. I'll freely admit that I may not have been as precise with my terms as I should have been, but I was writing quickly. Interesting that all you experts that were so quick to jump in my ****, didn't put out any effort to answer the question in any detail.
Last edited by Z28SORR; Dec 8, 2004 at 03:55 PM.
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Joined: Aug 2002
Posts: 2,325
From: BC
Re: descreening maf
If your going to answer something in detail i would suggest you at least be accurate. Otherwise your no better than someone answering with less detail anyways. Were not mind readers, we can't tell your writing something quickly.
Anyhow, regarding turbulant airlfow, if you look at the stock intake it looks VERY turbulant to me (A sharp bend AND giant kink in the piece to fit around the radiator). The K&N system i have looks a bit less but its still coming over a bend. Some people have a ram air intake (not the SS scoop) which in that case I would agree the airflow is probably not very turbulant at all, descreen it if you like. But for anyone else its arguable that you could be throwing it off. I think of it kind of like throwing tiny ping-pong ***** quickly through your intake, a straight intake will probably be fine, but any bend or kink just before the maf is gona mean a good bit of turbulance.
"I was wondering if it would be alright to run my car without the maf screen and if it would hurt or help anything."
I think people were just trying to answer that question, and the answer is "It can help, but its possible it'll hurt more than help."
Anyhow, regarding turbulant airlfow, if you look at the stock intake it looks VERY turbulant to me (A sharp bend AND giant kink in the piece to fit around the radiator). The K&N system i have looks a bit less but its still coming over a bend. Some people have a ram air intake (not the SS scoop) which in that case I would agree the airflow is probably not very turbulant at all, descreen it if you like. But for anyone else its arguable that you could be throwing it off. I think of it kind of like throwing tiny ping-pong ***** quickly through your intake, a straight intake will probably be fine, but any bend or kink just before the maf is gona mean a good bit of turbulance.
"I was wondering if it would be alright to run my car without the maf screen and if it would hurt or help anything."
I think people were just trying to answer that question, and the answer is "It can help, but its possible it'll hurt more than help."
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Joined: Apr 2003
Posts: 1,591
From: PA
Re: descreening maf
I've performed testing on the MAF in both the ram air and stock airbox configurations. I did this back in May and have been too lazy to type of the results into a post until now.
-----------------------------------------------------------------------
All values listed above were avgs of 3 trials and frequency output was converted to grams per second using the stock PCM tables then converted to CFM at standard conditions. Our blower (used for suction so not to introduce turbulence from the blades) was rated by the manufacturer at 405cfm so our readings were consistent with the expected flow rate. 400 cfm corresponds to approximately 4000 rpms WOT on a 350ci engine. The MAF frequency output was logged using a digital oscilloscope and frequency extracted using Fast Fourier Transform.
------------------------------------------------------------------------
In both of the below trials the turbulence of the flow into the MAF was held constant and restriction of the intake setup was varied by a) using no screen and b) placing the screen after the MAF. Using a constant overall pressure drop we measured:
a) 430.9 CFM with a .6cfm deviation in flow with no screen in the intake setup
b) 415.3 CFM with a 1.4 cfm deviation for flow with the screen mounted downstream (behind) the MAF
We can conclude that the screen represents ~15 cfm reduction in steady state flow for a constant pressure differential(constant manifold vacuum).
----------------------------------------------------------------------
Next we placed the screen in front of the MAF. This purpose of this trail was to hold the actual flowrate constant relative to the trial with the screen restriction placed behind the MAF. With constant actual flowrate we can compare changes in MAF output due to changes in the level of turbulence present in the flow.
415.3 CFM with a 1.4 cfm deviation, screen mounted behind the MAF
419.2 CFM with a .6 cfm deviation with the screen in front of the MAF (stock configuration)
Therefore with constant actual flowrate the MAF sensor output increased by ~4 cfm with the screen in stock configuration in front of the MAF.
---------------------------------------------------------------------
Conclusion, a couple free ponies for a ram air car and the screen does not significantly affect the calibration of the MAF for straight ram air type setup.
Remember, and engine has transient/dynamic flow. Treat these results as a steady state measurement of just one component of a complex system. Just like flowbench numbers cannot exactly predict a horsepower gain neither can these results. They do agree with most peoples dyno results that the screen follows the laws of physics and is a restriction to flow.
----------------------------------------------------------------------
The data from the more turbulent stock airbox configuration did not allow us to draw hard conclusions due to our inability to recreate the restriction and hold actual flowrate constant. Explanation of those results is difficult without the use of diagrams, pictures of the test equipment, and an advanced understanding of fluid flow so i won't put those here for people to draw conclusions without all the relevant information.
-brent
P.S. I haven't read this entire thread, i just felt guilty because I have some hard numbers and haven't shared them.
-----------------------------------------------------------------------
All values listed above were avgs of 3 trials and frequency output was converted to grams per second using the stock PCM tables then converted to CFM at standard conditions. Our blower (used for suction so not to introduce turbulence from the blades) was rated by the manufacturer at 405cfm so our readings were consistent with the expected flow rate. 400 cfm corresponds to approximately 4000 rpms WOT on a 350ci engine. The MAF frequency output was logged using a digital oscilloscope and frequency extracted using Fast Fourier Transform.
------------------------------------------------------------------------
In both of the below trials the turbulence of the flow into the MAF was held constant and restriction of the intake setup was varied by a) using no screen and b) placing the screen after the MAF. Using a constant overall pressure drop we measured:
a) 430.9 CFM with a .6cfm deviation in flow with no screen in the intake setup
b) 415.3 CFM with a 1.4 cfm deviation for flow with the screen mounted downstream (behind) the MAF
We can conclude that the screen represents ~15 cfm reduction in steady state flow for a constant pressure differential(constant manifold vacuum).
----------------------------------------------------------------------
Next we placed the screen in front of the MAF. This purpose of this trail was to hold the actual flowrate constant relative to the trial with the screen restriction placed behind the MAF. With constant actual flowrate we can compare changes in MAF output due to changes in the level of turbulence present in the flow.
415.3 CFM with a 1.4 cfm deviation, screen mounted behind the MAF
419.2 CFM with a .6 cfm deviation with the screen in front of the MAF (stock configuration)
Therefore with constant actual flowrate the MAF sensor output increased by ~4 cfm with the screen in stock configuration in front of the MAF.
---------------------------------------------------------------------
Conclusion, a couple free ponies for a ram air car and the screen does not significantly affect the calibration of the MAF for straight ram air type setup.
Remember, and engine has transient/dynamic flow. Treat these results as a steady state measurement of just one component of a complex system. Just like flowbench numbers cannot exactly predict a horsepower gain neither can these results. They do agree with most peoples dyno results that the screen follows the laws of physics and is a restriction to flow.
----------------------------------------------------------------------
The data from the more turbulent stock airbox configuration did not allow us to draw hard conclusions due to our inability to recreate the restriction and hold actual flowrate constant. Explanation of those results is difficult without the use of diagrams, pictures of the test equipment, and an advanced understanding of fluid flow so i won't put those here for people to draw conclusions without all the relevant information.
-brent
P.S. I haven't read this entire thread, i just felt guilty because I have some hard numbers and haven't shared them.
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Joined: Nov 2001
Posts: 3,515
From: Kansas
Re: descreening maf
Originally Posted by Z28SORR
Mass Air Flow Sensor (MAF) - The mass air flow sensor is positioned in the air intake duct or manifold and measures the mass of incoming air. From this acquired data the ECU calculates the required fuel for the specific air mass flow rate. The MAF works on the hot wire or hot film concept. The hot wire/film is maintained at a constant calibrated temperature. The passing air cools down the hot wire/film and the added energy required to maintain the calibrated temperature is directly proportional to the mass of air passing by the hot wire. The MAF also compensates for humidity as humid, denser or cooler air, absorbs more heat from the sensor, requiring more current to maintain the calibration temperature.
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tommalcolm
Computer Diagnostics and Tuning
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Sep 11, 2015 03:39 PM
