LilYellowZQ8
12-07-04, 07:29 PM
Written by Jedi Master.
Today’s engines functions with 14.7 parts of air to only 1 part of fuel, more than enough airflow is supplied with stock/aftermarket intake systems, thanks to over engineering by auto manufacturers. Add CAFE standards and smaller injectors, most engines are overly lean and do not need more “airflowâ€.
The idea of putting higher flow MAF/Ported on our cars is for WOT power and WOT upper RPM flow rate capability. Again, you CAN NOT use "more airflow with larger MAF's or TB's. Your engine uses as much air as it can. If properly metered the size is not the issue. Just because you have a larger MAF or TB doesn't mean you are getting in MORE air.
You find many more owners complaining about knock and or a misfire, which clearly says engine is running too lean, or too much timing, adding more airflow does not solve that problem. Then there are issues springing up about surging, bad idle, and problems when the cruise control is on, that is hunting.
So Aftermarket ends and or Porting the stock unit.
Engines are not going lean because a ported MAF/Aftermarket ends were installed, they are going lean because the same amount of air is still going into the engine for a given state/load, BUT the MAF is NOT reporting the true flow. A ported MAF will under-report the amount of air going into the engine. The PCM gets a lower frequency value from the same amount of air, due to ported MAF/ Aftermarket ended and calculate the correct amount of fuel for the reported flow rate, but its wrong, too little fuel is sent into the combustion chamber and the engine is running lean.
GMS non “C†model.
This is merely a stock in disguise. It is a, A/C Delco metering unit with oversized ends. So what is stated above holds true. Some people report some very minimal gains using these or other aftermarket MAFs, this is rare but due to the fact they were running to the rich side, some do, and this change leaned them out. Not a correct fix, but did work.
GMS “C†and Jet Etc.
A calibrated MAF is nothing more then modifying the MAF circuit with a constant, acting like a Air Fuel Translator, but not allowing end user to make changes, thus if it was set for 10% richer that is then forced upon all fuel trim cells if they were that lean or not. Remember we do not all modify or engines the same, but these models are identical in output readings. Change of MAF signal on its own effects delivered torque, line pressure and idle circuit.
So what do we do?
There are two ways to make a MAF of different size work.
1) You leave the stock tables in the PCM and calibrate the MAF to match those tables, which to this point hasn’t been done nor can it be accurate due to conditions, different types of modifying the engine etc.
2) You leave the different diameter MAF untouched and calibrated the PCM table to match the MAF output. Most don’t have this luxury, or it takes knowledgeable people with the tools to reflash and a diagnostic dyno.
You must re-calibrate the MAF so the PCM will put in the right amount of fuel! If you are clever person, you can re-calibrate the MAF table across all RPMs to get the LTFTs backed to where they were stock. But most of us prefer a slightly negative LTFT values. In doing this, you are not faking out the PCM, you are correcting a table that was thrown out of calibration because an engineering design change was made to the MAF.
Are these units ever needed, yes, once you have surpassed roughly 70 horsepower over stock via. a S/C, Turbo or some serious internal work. Then some of these units have the ability to read higher amounts of air than the stock MAF can report. But this will require a diagnostic dyno and the tools for proper reprogramming.Hello Boys and Girls we have and update to add to the MAF mystery. Ive done alot of toying and testing since this first series of posts with the Newer Blazer I required. I've also got more information from the aftermarket and also Delphi Auotmotive which I will share in this post.
Now to continue from the IS YOUR MOTOR GETTING ALL THE AIR IT CAN!! If after testing to see if 0 vacuum has taken place removing the air filter and you see its very slow to respond, but does make it you have a 2 fold problem. One your not running a cat back, or even adding headers so this isnt completely for you, but you could do this. Now for people running semi restricted modified exhaust and still see this slow reaction to 0 vacuum, you have a restriction taking place thats slowing it. Oh no, here I go, against the grain of the last series of posts. Remove your MAF screen and restest, they can be removed with a good exacto knife in one piece and reistalled later with something like a thin coat of JBweld or good epoxy glue. Now once the MAF screen is removed, restest and I bet 0 vacuum is attained very quickly. Now with the screen out add back on the filter system and retest, if it shows 0 vacuum, no problem, vacuum, you need a larger freeier flowing filter.
OH MY GOD OBI WENT AGAINST HIMSELF AND TOLD ME TO REMOVE MY SCREEN, HAS HE LOST IT???
NO OBI DID NOT LOSE IT!!!!! OBI LEARNED SOMETHING!!
OK GM's box intake system. Large box, little opening in front, made so you cant hear the vacuum created. It is dead in line to the MAF , but lacks good flow properties. The screen and center bar we all know is there to create a more balanced flow accross the MAF wires for a proper reading, but can impede flow.
OK, aftermarket air systems- They all use a coned filter and most use a curved intake tube to locate the filter behind the headlight air area to draw more cooler air in and some have shields to impede against underhood heat.
First now why they use coned filters??? What do they do?
Having a \/ shape air enters at different angles and speed when going throw the filter into the tube, creates a Vortex. The Vortex compacts the air charge some, OHHH GOODIE, yes it'll add more air in a smaller space BUT slows down velocity while doing so. You can experience this when you mash the throttle at times and feel a stumble to it. This is part of the gain you get from running a free flowing cone it more air. But what they dont mention is this Vortex which contain less air in the center than outsides goes through the MAF and the MAF cant detect it all. Anytime a MAF reads leaner vs same throttle position, it will add some timing, that they dont tell you. So you get maybe 5-7 for the air extra and 2-5 for the timing extra.
Second why the bend has a 2 fold purpose?? We know to locate the filter near the cooler air source is a good thing, but it has another purpose. Like anything else under movement like this, the majority of anything will take the quickest route which is the short side of the bend. Just so happens the bend is on the bottom and the MAF wires dont all go to the bottom of you MAF housing so more air passed unseen, supports more timing.
Now all well and good but what are you getting at??? OK with the screen in , it will help correct some of these air flow properties which can make ther MAF read to lean, but the MAF screen slowed the 0 vacuum area which I would like gone for maximum air flow at all times.
Youve seen me post about using the New Airaid intake system that mounts directly on the stock box, utilizes a cone filter etc. I modified the stock box using a 2 inch PVC pipe and ducted in throught the inner fender to grab more cool air. I like the system, worked as good as the others for much more money, but I did this for a reason. I learned all this stuff about air flow properties before but never had the time or monies to correct them on the Noma and wasnt 100% sure it was all correct. I removed the screen from my MAF to correct a slow 0 vacuum reaction, but it hampered the basic running of the truck due to air flow being undetected, hum how to fix this??? Well I thought about it and poked around and seem to have found the solution and best possible combo of least restriction, most available air, and MAF Readings nearer the stock reporting.
I'm using a K&N X top cone filter. It still semi compresses the air due to its cone, but at the same time air passes in the front end right into the MAF wires. Using the Autotap and doing some data logging over the last 2 months. I took completely stock MAF, timing values and 02 readings, Ones using my K&N from the last truck, ones from the Airaid and then with the K&N Xtop. Used a descreened and screened MAF, ""Thanks Supercharged ZQ-8 for the extra"" and ran all the combo's.
I made a spread sheet to compile and try to decipher what it all meaned and came up with this. Anything outflowed the stock setup as far as 02 readings and timing values. The K&N went the leanest in readings but was caught getting timing retard with the screen out. The best combo for accuracy and max timing was the Airaid and K&N Xtop, I saw the closest readings as far as MAF readings against stock, but always had more timing involved ( 1 degree on average) with no signs of knock tetard. I also noticed something else, when you get a very light unaudible ping, the comp sometimes confuses this as a misfire, I would get knock retard and or misfires in the same throttle movements supporting that notion!!
So I guess you can remove the screen with no negative effects and a minor gain if its done right.
Today’s engines functions with 14.7 parts of air to only 1 part of fuel, more than enough airflow is supplied with stock/aftermarket intake systems, thanks to over engineering by auto manufacturers. Add CAFE standards and smaller injectors, most engines are overly lean and do not need more “airflowâ€.
The idea of putting higher flow MAF/Ported on our cars is for WOT power and WOT upper RPM flow rate capability. Again, you CAN NOT use "more airflow with larger MAF's or TB's. Your engine uses as much air as it can. If properly metered the size is not the issue. Just because you have a larger MAF or TB doesn't mean you are getting in MORE air.
You find many more owners complaining about knock and or a misfire, which clearly says engine is running too lean, or too much timing, adding more airflow does not solve that problem. Then there are issues springing up about surging, bad idle, and problems when the cruise control is on, that is hunting.
So Aftermarket ends and or Porting the stock unit.
Engines are not going lean because a ported MAF/Aftermarket ends were installed, they are going lean because the same amount of air is still going into the engine for a given state/load, BUT the MAF is NOT reporting the true flow. A ported MAF will under-report the amount of air going into the engine. The PCM gets a lower frequency value from the same amount of air, due to ported MAF/ Aftermarket ended and calculate the correct amount of fuel for the reported flow rate, but its wrong, too little fuel is sent into the combustion chamber and the engine is running lean.
GMS non “C†model.
This is merely a stock in disguise. It is a, A/C Delco metering unit with oversized ends. So what is stated above holds true. Some people report some very minimal gains using these or other aftermarket MAFs, this is rare but due to the fact they were running to the rich side, some do, and this change leaned them out. Not a correct fix, but did work.
GMS “C†and Jet Etc.
A calibrated MAF is nothing more then modifying the MAF circuit with a constant, acting like a Air Fuel Translator, but not allowing end user to make changes, thus if it was set for 10% richer that is then forced upon all fuel trim cells if they were that lean or not. Remember we do not all modify or engines the same, but these models are identical in output readings. Change of MAF signal on its own effects delivered torque, line pressure and idle circuit.
So what do we do?
There are two ways to make a MAF of different size work.
1) You leave the stock tables in the PCM and calibrate the MAF to match those tables, which to this point hasn’t been done nor can it be accurate due to conditions, different types of modifying the engine etc.
2) You leave the different diameter MAF untouched and calibrated the PCM table to match the MAF output. Most don’t have this luxury, or it takes knowledgeable people with the tools to reflash and a diagnostic dyno.
You must re-calibrate the MAF so the PCM will put in the right amount of fuel! If you are clever person, you can re-calibrate the MAF table across all RPMs to get the LTFTs backed to where they were stock. But most of us prefer a slightly negative LTFT values. In doing this, you are not faking out the PCM, you are correcting a table that was thrown out of calibration because an engineering design change was made to the MAF.
Are these units ever needed, yes, once you have surpassed roughly 70 horsepower over stock via. a S/C, Turbo or some serious internal work. Then some of these units have the ability to read higher amounts of air than the stock MAF can report. But this will require a diagnostic dyno and the tools for proper reprogramming.Hello Boys and Girls we have and update to add to the MAF mystery. Ive done alot of toying and testing since this first series of posts with the Newer Blazer I required. I've also got more information from the aftermarket and also Delphi Auotmotive which I will share in this post.
Now to continue from the IS YOUR MOTOR GETTING ALL THE AIR IT CAN!! If after testing to see if 0 vacuum has taken place removing the air filter and you see its very slow to respond, but does make it you have a 2 fold problem. One your not running a cat back, or even adding headers so this isnt completely for you, but you could do this. Now for people running semi restricted modified exhaust and still see this slow reaction to 0 vacuum, you have a restriction taking place thats slowing it. Oh no, here I go, against the grain of the last series of posts. Remove your MAF screen and restest, they can be removed with a good exacto knife in one piece and reistalled later with something like a thin coat of JBweld or good epoxy glue. Now once the MAF screen is removed, restest and I bet 0 vacuum is attained very quickly. Now with the screen out add back on the filter system and retest, if it shows 0 vacuum, no problem, vacuum, you need a larger freeier flowing filter.
OH MY GOD OBI WENT AGAINST HIMSELF AND TOLD ME TO REMOVE MY SCREEN, HAS HE LOST IT???
NO OBI DID NOT LOSE IT!!!!! OBI LEARNED SOMETHING!!
OK GM's box intake system. Large box, little opening in front, made so you cant hear the vacuum created. It is dead in line to the MAF , but lacks good flow properties. The screen and center bar we all know is there to create a more balanced flow accross the MAF wires for a proper reading, but can impede flow.
OK, aftermarket air systems- They all use a coned filter and most use a curved intake tube to locate the filter behind the headlight air area to draw more cooler air in and some have shields to impede against underhood heat.
First now why they use coned filters??? What do they do?
Having a \/ shape air enters at different angles and speed when going throw the filter into the tube, creates a Vortex. The Vortex compacts the air charge some, OHHH GOODIE, yes it'll add more air in a smaller space BUT slows down velocity while doing so. You can experience this when you mash the throttle at times and feel a stumble to it. This is part of the gain you get from running a free flowing cone it more air. But what they dont mention is this Vortex which contain less air in the center than outsides goes through the MAF and the MAF cant detect it all. Anytime a MAF reads leaner vs same throttle position, it will add some timing, that they dont tell you. So you get maybe 5-7 for the air extra and 2-5 for the timing extra.
Second why the bend has a 2 fold purpose?? We know to locate the filter near the cooler air source is a good thing, but it has another purpose. Like anything else under movement like this, the majority of anything will take the quickest route which is the short side of the bend. Just so happens the bend is on the bottom and the MAF wires dont all go to the bottom of you MAF housing so more air passed unseen, supports more timing.
Now all well and good but what are you getting at??? OK with the screen in , it will help correct some of these air flow properties which can make ther MAF read to lean, but the MAF screen slowed the 0 vacuum area which I would like gone for maximum air flow at all times.
Youve seen me post about using the New Airaid intake system that mounts directly on the stock box, utilizes a cone filter etc. I modified the stock box using a 2 inch PVC pipe and ducted in throught the inner fender to grab more cool air. I like the system, worked as good as the others for much more money, but I did this for a reason. I learned all this stuff about air flow properties before but never had the time or monies to correct them on the Noma and wasnt 100% sure it was all correct. I removed the screen from my MAF to correct a slow 0 vacuum reaction, but it hampered the basic running of the truck due to air flow being undetected, hum how to fix this??? Well I thought about it and poked around and seem to have found the solution and best possible combo of least restriction, most available air, and MAF Readings nearer the stock reporting.
I'm using a K&N X top cone filter. It still semi compresses the air due to its cone, but at the same time air passes in the front end right into the MAF wires. Using the Autotap and doing some data logging over the last 2 months. I took completely stock MAF, timing values and 02 readings, Ones using my K&N from the last truck, ones from the Airaid and then with the K&N Xtop. Used a descreened and screened MAF, ""Thanks Supercharged ZQ-8 for the extra"" and ran all the combo's.
I made a spread sheet to compile and try to decipher what it all meaned and came up with this. Anything outflowed the stock setup as far as 02 readings and timing values. The K&N went the leanest in readings but was caught getting timing retard with the screen out. The best combo for accuracy and max timing was the Airaid and K&N Xtop, I saw the closest readings as far as MAF readings against stock, but always had more timing involved ( 1 degree on average) with no signs of knock tetard. I also noticed something else, when you get a very light unaudible ping, the comp sometimes confuses this as a misfire, I would get knock retard and or misfires in the same throttle movements supporting that notion!!
So I guess you can remove the screen with no negative effects and a minor gain if its done right.