MAF Screen Removal - Rich or Lean Effect?
Thread Starter
Le Mans Master
Joined: Aug 2002
Posts: 8,472
Likes: 38
From: Houston TX
St. Jude Donor '11
MAF Screen Removal - Rich or Lean Effect?
I know people argue over removing the MAF screen providing any horsepower or not. Whether it could add ANY horsepower would depend on whethe rit induces a leaner or richer condition and whether your engine is requiring that condition to make more power.
I did some EFI-Live tapping. My LTFT's were all negative and my O2's were 900+ under WOT. I'm told if I lean it out a bit to say 880-890 mV (preferrably with a MAFT) I would see a noticable difference. Has anyone tapped before and after to see if it creates a slightly leaner or richer condition, or nothing at all?
I've been debating removing the screen for a while. I would think that one of two things would happen:
1. The MAF is calibrated solely on the diameter of the MAF. The extra area that the screen was taking up would allow extra flow when removed(I know we're talking minimal here) that would be detected in a tap. The calibration of the MAF would not be affected.
2. The MAF's calibration takes into account the restriction the screen has, effectively decreasing the diameter of the MAF. Removing the screen would be like 75mm MAF resistors in a 75.05mm MAF housing which would create a rich? condition if anything.
What do you guys think. Please no "Removing the MAF screen is a waste of time...yada yada posts".
I did some EFI-Live tapping. My LTFT's were all negative and my O2's were 900+ under WOT. I'm told if I lean it out a bit to say 880-890 mV (preferrably with a MAFT) I would see a noticable difference. Has anyone tapped before and after to see if it creates a slightly leaner or richer condition, or nothing at all?
I've been debating removing the screen for a while. I would think that one of two things would happen:
1. The MAF is calibrated solely on the diameter of the MAF. The extra area that the screen was taking up would allow extra flow when removed(I know we're talking minimal here) that would be detected in a tap. The calibration of the MAF would not be affected.
2. The MAF's calibration takes into account the restriction the screen has, effectively decreasing the diameter of the MAF. Removing the screen would be like 75mm MAF resistors in a 75.05mm MAF housing which would create a rich? condition if anything.
What do you guys think. Please no "Removing the MAF screen is a waste of time...yada yada posts".
Melting Slicks
Joined: Mar 2001
Posts: 3,250
Likes: 60
From: League City TX
Re: MAF Screen Removal - Rich or Lean Effect? (5 Liter Eater)
I did some EFI-Live tapping. My LTFT's were all negative and my O2's were 900+ under WOT. I would see a noticable difference. Has anyone tapped before and after to see if it creates a slightly leaner or richer condition, or nothing at all?
1. Computer sees more air going through the MAF at all times.
2. Therefore, in power enrighment mode (WOT), it throws extra fuel at the engine.
3. The enrichment is shown in LTFT
4. I would not rely on the 02s for WOT readings.
Pull the screen, get a Predator or LS1 Edit, book 30 minutes on the Dyno and straighten out the fuel curve.
Le Mans Master
Joined: Apr 2001
Posts: 8,133
Likes: 144
From: Ex-SF Bay Area; now happily Denver area
Re: MAF Screen Removal - Rich or Lean Effect? (binksZ06)
I don't know much about this stuff but when I got mine dynoed, I had done a couple of things, including taking out the MAF screen and upgrading to a Donaldson from a different hi-flow filter. I put in a MAFT at the time also.
I just pulled the dyno graphs and it looks like I may have gained maybe 1 or 2 horsepower (but that's within the dyno error range) by leaning out the air-fuel ratio. At 2500 rpm to 6K, stock went from about 15 to 13 (3500 rpms) and then downn to about 11.5 at 6K rpms. With 2% lean, it went from 15 to 14 (3500 rpms) to a little less than 13 at 6K rpms. At 4% lean, it went from 15 and dropped faster to 13 (3500 rpms) and was pretty flat all the way to 6K rpms. The 4% lean looks like the best graph, dropping quickly to 13 and staying there throughout the rpm range.
I don't know if this helps much but maybe it will give a little more info. The dyno guy said that the car's computer had done a pretty good job of correcting for the changes.
I just pulled the dyno graphs and it looks like I may have gained maybe 1 or 2 horsepower (but that's within the dyno error range) by leaning out the air-fuel ratio. At 2500 rpm to 6K, stock went from about 15 to 13 (3500 rpms) and then downn to about 11.5 at 6K rpms. With 2% lean, it went from 15 to 14 (3500 rpms) to a little less than 13 at 6K rpms. At 4% lean, it went from 15 and dropped faster to 13 (3500 rpms) and was pretty flat all the way to 6K rpms. The 4% lean looks like the best graph, dropping quickly to 13 and staying there throughout the rpm range.
I don't know if this helps much but maybe it will give a little more info. The dyno guy said that the car's computer had done a pretty good job of correcting for the changes.
