Thinking about descreening your MAF? Think again...
Thread Starter
Joined: Nov 2001
Posts: 927
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From: Michigan, the land of cold
Thinking about descreening your MAF? Think again... There are many people that swear if you remove your screen on the MAF you'll gain power. Perhaps you will, perhaps you won't.
You most likely will either lose power or stay the same (if you are lucky). Most guys won't bother with tuning a car that's had anything done to the sensor (porting, polishing, descreen). It's a real pain to deal with, especially when you realize that the air will swirl around inside the sensor instead of going directly past the elements. This causes all sorts of odd anomalies in the data the PCM is receiving.
I've compiled some data with HPTuners that you should look at. Basically, I've removed the screen on the MAF was reading Dynamic Air and the MAF Frequency. The MAF frequency should match within reason of incoming air, shouldn't it?
See attached Excel spreadsheet. These runs were done one right after the other. Car was fully warmed up. Outside temp was in the mid 80's.
Maybe I'm barking up the wrong tree, but I know that with the MAF enabled the car has issues.
You most likely will either lose power or stay the same (if you are lucky). Most guys won't bother with tuning a car that's had anything done to the sensor (porting, polishing, descreen). It's a real pain to deal with, especially when you realize that the air will swirl around inside the sensor instead of going directly past the elements. This causes all sorts of odd anomalies in the data the PCM is receiving.
I've compiled some data with HPTuners that you should look at. Basically, I've removed the screen on the MAF was reading Dynamic Air and the MAF Frequency. The MAF frequency should match within reason of incoming air, shouldn't it?
See attached Excel spreadsheet. These runs were done one right after the other. Car was fully warmed up. Outside temp was in the mid 80's.
Maybe I'm barking up the wrong tree, but I know that with the MAF enabled the car has issues.
I have seen gains of around 5 rwhp by removing the screen on a 75mm maf and then tuning for it with no oddities or consequences. On the 85mm MAFs I prefer to have the screen in place if it came with one to keep the MAF signal more steady.
Thread Starter
Joined: Nov 2001
Posts: 927
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From: Michigan, the land of cold
Originally Posted by Alvin
I've tried descreening the MAF on the dyno several times and on several cars and it almost always equals 5rwhp 5ftlbs square and less than .25 (most of the time less) change in AFR.
Have you looked at the MAF readings?
Originally Posted by ChevyThunder17
5 HP could be just the car readjusting itself that it's being driven more aggressively, or that it's leaning out the car since it's seeing less air.
Have you looked at the MAF readings?
Have you looked at the MAF readings?
Last edited by NicD; Jul 4, 2006 at 05:04 PM.
I have had no troubles using a descreened truck MAF
with the truck table.
If the MAF airflow disagrees with dynamic airflow it is
because there is something else blended in, like the
speed density air value, smoothing or predictive
stuff.
If you have a bent intake tract then the screen has
a job to do. If yours is straight like an F-body, it is
only a bug sieve and a source of inlet drag.
MAF Hz is not the airflow value. MAF airflow g/sec
is what you want to put up against Dynamic Airflow
g/sec.
with the truck table.
If the MAF airflow disagrees with dynamic airflow it is
because there is something else blended in, like the
speed density air value, smoothing or predictive
stuff.
If you have a bent intake tract then the screen has
a job to do. If yours is straight like an F-body, it is
only a bug sieve and a source of inlet drag.
MAF Hz is not the airflow value. MAF airflow g/sec
is what you want to put up against Dynamic Airflow
g/sec.
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I have both a stock MAF and a severely ported / descreened MAF. There is a noticeable loss of power when I revert back to the stock MAF and table. Yes, it may take some time to tune and dial in your MAF if its been altered but Im a firm believer in the gains to be had. My ported MAF has to be scaled ~145%, so its flowing approximately 45% more air. I find it hard to believe there are no gains to be had here. IMO the stock MAF is more restrictive than a stock TB, which has been proven time and time again to show gains. Im also a big fan of MAF over SD tunes.
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Verdad Gallardo Thread Starter
Joined: Nov 2001
Posts: 927
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From: Michigan, the land of cold
Originally Posted by jimmyblue
I have had no troubles using a descreened truck MAF
with the truck table.
If the MAF airflow disagrees with dynamic airflow it is
because there is something else blended in, like the
speed density air value, smoothing or predictive
stuff.
If you have a bent intake tract then the screen has
a job to do. If yours is straight like an F-body, it is
only a bug sieve and a source of inlet drag.
MAF Hz is not the airflow value. MAF airflow g/sec
is what you want to put up against Dynamic Airflow
g/sec.
with the truck table.
If the MAF airflow disagrees with dynamic airflow it is
because there is something else blended in, like the
speed density air value, smoothing or predictive
stuff.
If you have a bent intake tract then the screen has
a job to do. If yours is straight like an F-body, it is
only a bug sieve and a source of inlet drag.
MAF Hz is not the airflow value. MAF airflow g/sec
is what you want to put up against Dynamic Airflow
g/sec.
I ran with MAF enabled and disabled. The frequency vs incomiing airflow varies depending on the sensor being used or not. You can tell with the LTFT's.
The air going through the MAF without a screen isn't going in straight. It's going to be irratic. When air blows, the molecules don't go straight, it varies. The point is no screen means that you are no longer accurately measuring the incoming air.
TECH Apprentice
Joined: Oct 2005
Posts: 320
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From: Norwalk, CT
Originally Posted by ChevyThunder17
I know it's not airflow value, it's a comparison of Hz vs. volume of air. The inconsistancies within the data is the point I'm demonstrating.
I ran with MAF enabled and disabled. The frequency vs incomiing airflow varies depending on the sensor being used or not. You can tell with the LTFT's.
The air going through the MAF without a screen isn't going in straight. It's going to be irratic. When air blows, the molecules don't go straight, it varies. The point is no screen means that you are no longer accurately measuring the incoming air.
I ran with MAF enabled and disabled. The frequency vs incomiing airflow varies depending on the sensor being used or not. You can tell with the LTFT's.
The air going through the MAF without a screen isn't going in straight. It's going to be irratic. When air blows, the molecules don't go straight, it varies. The point is no screen means that you are no longer accurately measuring the incoming air.
Thread Starter
Joined: Nov 2001
Posts: 927
Likes: 0
From: Michigan, the land of cold
Originally Posted by Dave88z
Why would the air going thru the MAF not be straight? If a length of intake before the MAF is straight then it will smooth out airflow. As prev stated, if the intake makes a sharp bend then a screen may be needed to help smooth the air flow for accurate readings.
Put it this way; they put it there for a purpose, and not to restrict airflow. (They do that by crimping the y-pipe on the drivers side of the car.) By removing the screen, it does introduce turbulence as a factor.
Originally Posted by Dave88z
Why would the air going thru the MAF not be straight? If a length of intake before the MAF is straight then it will smooth out airflow. As prev stated, if the intake makes a sharp bend then a screen may be needed to help smooth the air flow for accurate readings.
Originally Posted by TimZ28
WTF do you care?
It has been beaten to death. Results vary, and recalibrating the maf table is the biggest culprit to favorable gains.
It sounds like you have already made a decision and your looking for the data you want to see in the log.
As someone who has dynoed a few cars let me tell you I've tried this not on one occasion but a few and it works.
As someone who has dynoed a few cars let me tell you I've tried this not on one occasion but a few and it works.
Thread Starter
Joined: Nov 2001
Posts: 927
Likes: 0
From: Michigan, the land of cold
Originally Posted by Alvin
It sounds like you have already made a decision and your looking for the data you want to see in the log.
As someone who has dynoed a few cars let me tell you I've tried this not on one occasion but a few and it works.
As someone who has dynoed a few cars let me tell you I've tried this not on one occasion but a few and it works.
You can formulate your own conclusion from looking at the data. A small variation on the dyno could be a number of things. On the other hand when you are looking at the data that was logged, and when the frequency of the sensor doesn't sync up with the airflow the engine is seeing that's a problem.
Originally Posted by TimZ28
WTF do you care?
https://ls1tech.com/forums/showthrea...&highlight=MAF
http://delphi.com/pdf/techpapers/2000-01-0546.pdf
Originally Posted by ChevyThunder17
It's not looking for the data I want to see. It's what I am seeing. Lots of guys will tell you to leave the MAF screen in. Nobody has really shown anything conclusive. I've got actual data showing what the sensor is doing and what the engine is actually getting in regards to airflow. It's all over the place.
You can formulate your own conclusion from looking at the data. A small variation on the dyno could be a number of things. On the other hand when you are looking at the data that was logged, and when the frequency of the sensor doesn't sync up with the airflow the engine is seeing that's a problem.
You can formulate your own conclusion from looking at the data. A small variation on the dyno could be a number of things. On the other hand when you are looking at the data that was logged, and when the frequency of the sensor doesn't sync up with the airflow the engine is seeing that's a problem.
Originally Posted by ChevyThunder17
Nobody has really shown anything conclusive.