Understand how MAF works - DON'T DE-SCREEN IT!!
10-12-2004, 10:11 PM
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Understand how MAF works - DON'T DE-SCREEN IT!! A lot of people think that taking the screen off of the MAF will increase air flow. While this may be true, it will screw up the engine management system.
The Mass Air Flow (MAF) sensor utilises a heated element type of operation. A heated element in the MAF is placed in the air flow stream of the engine
intake system.
The heating element is maintained at a constant temperature differential above the air temperature. The amount of electrical power required to maintain the heated element at the proper temperature is a direct function of the mass flow rate of the air past the heated element.
Three sensing elements are used in this system. One senses ambient air temperature and uses two calibrated resistors to establish a voltage that is
always a function of ambient temperature. This ambient sensor is mounted in the lower half of the sensor housing.
The other two sensing elements are heated to a predetermined temperature that is significantly above ambient air temperature. The two heated elements are connected electrically in parallel and mounted directly in the air flow stream of the sensor housing. One sensor is in the top and the other sensor is in the bottom of the sensor housing. This is done so that the air meter is less sensitive to upstream dueling configurations that could skew the flow of air through the housing.
As air passes over the heated elements during engine operation they begin to cool. By measuring the amount of electrical power required to maintain
the heated elements at the predetermined temperature above ambient temperature the mass air flow rate can be determined.
Once the mass air flow sensor has developed an internal signal related to the mass air flow rate, it must send this information to the PCM. In order to
preserve the accuracy and resolution of the small voltage signal in the mass air flow sensor, it is converted to a frequency signal by a voltage oscillator and sent to the PCM.
The signal that is sent from the MAF sensor is sent in the form of a frequency output. A large quantity of air passing through the sensor (such as when accelerating) will be indicated as a high frequency output.
A small quantity of air passing through the sensor will be indicated as a low frequency output (such as when decelerating or at idle). Scan tools display MAF sensor information in frequency, and in grams per second. At idle the
readings should be low and increase with engine RPM.
If a problem occurs in the MAF sensor circuit, the PCM will store a DTC in its memory. The PCM will turn on the Check Powertrain Lamp, indicating there is a problem. If this occurs, the PCM will calculate a substitute mass air flow signal based on speed density RPM, MAP and IAT.
No field service adjustment is necessary or possible with the MAF sensor.
That's why the rule of thumbs is LIVE THE DAMN MAF ALONE!!!
The Mass Air Flow (MAF) sensor utilises a heated element type of operation. A heated element in the MAF is placed in the air flow stream of the engine
intake system.
The heating element is maintained at a constant temperature differential above the air temperature. The amount of electrical power required to maintain the heated element at the proper temperature is a direct function of the mass flow rate of the air past the heated element.
Three sensing elements are used in this system. One senses ambient air temperature and uses two calibrated resistors to establish a voltage that is
always a function of ambient temperature. This ambient sensor is mounted in the lower half of the sensor housing.
The other two sensing elements are heated to a predetermined temperature that is significantly above ambient air temperature. The two heated elements are connected electrically in parallel and mounted directly in the air flow stream of the sensor housing. One sensor is in the top and the other sensor is in the bottom of the sensor housing. This is done so that the air meter is less sensitive to upstream dueling configurations that could skew the flow of air through the housing.
As air passes over the heated elements during engine operation they begin to cool. By measuring the amount of electrical power required to maintain
the heated elements at the predetermined temperature above ambient temperature the mass air flow rate can be determined.
Once the mass air flow sensor has developed an internal signal related to the mass air flow rate, it must send this information to the PCM. In order to
preserve the accuracy and resolution of the small voltage signal in the mass air flow sensor, it is converted to a frequency signal by a voltage oscillator and sent to the PCM.
The signal that is sent from the MAF sensor is sent in the form of a frequency output. A large quantity of air passing through the sensor (such as when accelerating) will be indicated as a high frequency output.
A small quantity of air passing through the sensor will be indicated as a low frequency output (such as when decelerating or at idle). Scan tools display MAF sensor information in frequency, and in grams per second. At idle the
readings should be low and increase with engine RPM.
If a problem occurs in the MAF sensor circuit, the PCM will store a DTC in its memory. The PCM will turn on the Check Powertrain Lamp, indicating there is a problem. If this occurs, the PCM will calculate a substitute mass air flow signal based on speed density RPM, MAP and IAT.
No field service adjustment is necessary or possible with the MAF sensor.
That's why the rule of thumbs is LIVE THE DAMN MAF ALONE!!!
Descreen that sucker! 
10's of thousands of LS1 racers can't be wrong. 
10-12-2004, 11:11 PM
#5
When I bought my car a few years ago I removed the screen because I didn't know any better. HOWEVER, everybody predicts a dooms day forecast once your remove them, everything from incorrect A/F ratio, low trans pressure ect. However my car runs just fine, transpressure is great, and it ran 13.00's with basically no mods before I had my converter and tuning.
10-13-2004, 01:44 AM
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That HUGE explaination was all very interesting but it does not support your assertion that removing the screen will have a determential affect.
I bought an oversized 85mm with a screen. It works fine.
Can you write a huge narrative on why you should not hog-out the ridge in the throttle body?
I bought an oversized 85mm with a screen. It works fine.
Can you write a huge narrative on why you should not hog-out the ridge in the throttle body?
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10-13-2004, 02:10 AM
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In fact, no because ported TBs are a good thing. My Shaner S3 will show up soon.
The MAF has 3 sensitive components that will only send the right info to the PCM when the air flow follows the guided pattern the screen creates. Without the screen you may free up the passage a little bit but uneven amounts of air will hit the tiny sensors 100s of times, all the time, and that's not good -- note that this was said by a GM engineer, not me. Don't shoot the messenger
The MAF has 3 sensitive components that will only send the right info to the PCM when the air flow follows the guided pattern the screen creates. Without the screen you may free up the passage a little bit but uneven amounts of air will hit the tiny sensors 100s of times, all the time, and that's not good -- note that this was said by a GM engineer, not me. Don't shoot the messenger
Can you write a huge narrative on why you should not hog-out the ridge in the throttle body?
10-13-2004, 02:34 AM
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Was the GM engineer you talked with the same guy that designed the valve train rockers that rotinely explode their needle bearings and the oil pump that takes a wiz at 6,000 RPM? If no, maybe he was the guy that designed the pistons and rings that constantly slap when the engine is cold.
Fact is with all the factory defects designed into the Gen3 motors I would not place too much reliance on GM engineers.
Fact is with all the factory defects designed into the Gen3 motors I would not place too much reliance on GM engineers.
10-13-2004, 03:13 AM
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My guess is that engineering is a field of compromises. Pressure comes from everywhere - financial departments, emissions (i.e. government), etc... When banks stop having a strangle hold on all aspects of production in US maybe we'll start seeing higher quality products.
I don't want to transform this in a political thread. And I give the GM guy some credibility after all he is the one who dedicated his life to car electronics, not me.
Unfortunately, when everything is about "the bottom line" we all lose.
I don't want to transform this in a political thread. And I give the GM guy some credibility after all he is the one who dedicated his life to car electronics, not me.
Unfortunately, when everything is about "the bottom line" we all lose.
Originally Posted by robertbartsch
Was the GM engineer you talked with the same guy that designed the valve train rockers that rotinely explode their needle bearings and the oil pump that takes a wiz at 6,000 RPM? If no, maybe he was the guy that designed the pistons and rings that constantly slap when the engine is cold.
Fact is with all the factory defects designed into the Gen3 motors I would not place too much reliance on GM engineers.
Fact is with all the factory defects designed into the Gen3 motors I would not place too much reliance on GM engineers.
10-13-2004, 05:51 AM
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Originally Posted by Mike K.
Doesn't the ls6 come from the factory descreened?
2002+ Z06 85mm, no screen
Not sure about the LS6 in the CTSV
Mike
10-13-2004, 07:34 AM
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The screen is a flow straightener. What it does is remove turbulence from the airflow. If the air flowing through the mass flow sensor is not smooth there is no way the sensor can work. If you have a lid it will smooth the airflow and u may not need a screen. GM removes the screen because they cost money, not for better performance. The horsepower lose with the screen is small. The MAF is calibrated, that is why it is not a good idea to port it or change it in any why. The MAF is there to account for differences in each motor. You can get rid of it if u do a good tune on your car, but unless you want to do a lot of tuning on your car do not touch it.
10-13-2004, 07:39 AM
#15
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While this is a debate for N/A users, as a dry N20 user, I have to descreen it.
And I speak from experience, one day at the track i went from 100 shot to 150 and after the run, I couldn't figure out why i had only gained .1 sec. Fuel was adequate, bigger injectors so I checked for MAF problems. I found that the screen had gathered ice to the point of blocking 50% of the inlet.
So I descreened it before the next heat, double checked with ATAP, all parameters within accepatable limits, I increased 5% fuel just for safety margin and off I went.
.46 reduction in time from 100 shot screened.
This is all the proof I need.
And I speak from experience, one day at the track i went from 100 shot to 150 and after the run, I couldn't figure out why i had only gained .1 sec. Fuel was adequate, bigger injectors so I checked for MAF problems. I found that the screen had gathered ice to the point of blocking 50% of the inlet.
So I descreened it before the next heat, double checked with ATAP, all parameters within accepatable limits, I increased 5% fuel just for safety margin and off I went.
.46 reduction in time from 100 shot screened.
This is all the proof I need.
10-13-2004, 08:32 AM
#16
I guess you know more than the GM and Delphi engineers who design these...they removed the screen on the '02 and up Z06 system...
http://www.c5registry.com/2k2z06/page3.htm
-Kevin
http://www.c5registry.com/2k2z06/page3.htm
-Kevin
Originally Posted by WS6freak
A lot of people think that taking the screen off of the MAF will increase air flow. While this may be true, it will screw up the engine management system.
LIVE THE DAMN MAF ALONE!!!
LIVE THE DAMN MAF ALONE!!!
10-13-2004, 08:35 AM
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Airflow evenness across the MAF orifice is key to
"ideal" calibration (embedded in the factory cal is
the ratio of total airflow to "sensible airflow" that
actually affects the wire resistance.
Two questions pertain (but are only answerable
after the fact) -
- is the air flow in your intake tract "even enough"
at the point where it reaches the MAF and stay
that way over the flow range? That looks like a
"yes" for the F-bodies, an "uhmmm... not quite"
for the 'vettes (owing to the air bridge centrifugal
bias) and a beats-the-hell-out-of-me on the trucks.
- If the mixture is biased off from cal basis, can
you correct for it? Like for example the Z06 MAF is
descreened yet the air bridge flow bias remains. The
Z06 MAF table varies slightly from the truck MAF
table, apparently accounting for this.
I run a descreened truck MAF on an F-body and used
the screened truck table with better results than the
Z06 table.
For an F-body, if you can tune, I say descreen the
sucker, put the late Holden table in, and rock on.
"ideal" calibration (embedded in the factory cal is
the ratio of total airflow to "sensible airflow" that
actually affects the wire resistance.
Two questions pertain (but are only answerable
after the fact) -
- is the air flow in your intake tract "even enough"
at the point where it reaches the MAF and stay
that way over the flow range? That looks like a
"yes" for the F-bodies, an "uhmmm... not quite"
for the 'vettes (owing to the air bridge centrifugal
bias) and a beats-the-hell-out-of-me on the trucks.
- If the mixture is biased off from cal basis, can
you correct for it? Like for example the Z06 MAF is
descreened yet the air bridge flow bias remains. The
Z06 MAF table varies slightly from the truck MAF
table, apparently accounting for this.
I run a descreened truck MAF on an F-body and used
the screened truck table with better results than the
Z06 table.
For an F-body, if you can tune, I say descreen the
sucker, put the late Holden table in, and rock on.
10-13-2004, 08:58 AM
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Yes GM removed the screen but the calibrations are different from 01 and 02+ these changes are reflect in the freqency tables like jimmy has said in his previous post
The tables can be found here
http://www.ls1howto.com/index.php?ar...db983cc3069eb7
The tables can be found here
http://www.ls1howto.com/index.php?ar...db983cc3069eb7
10-13-2004, 09:40 AM
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So some of you are saying that porting and de screening are a gamble? As long as the air flows properly it could work? I can't see the air not flowing properly. It only has one place to go. And the air that passes through it is controlled by the needs of the engine with the TB. So air flow should always be fluid and smooth. I am not criticizing anyone here, just educating myself. I have a ported and de screened MAF. I have done the resistor mod and I have no problems. When I go from !MAF to stock, there is a SOP difference. I guess my question is why does it work for some and not for others? Or does it work but no one that does not believe in it has tried it for themselves. Again, not burning, just learning.