Porting MAF, does it run rich or lean?
Thread Starter
Melting Slicks
Joined: May 2005
Posts: 3,394
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From: Leon Iowa
St. Jude Donor '06-'07-'08-'09
Porting MAF, does it run rich or lean?
I have heard that it will lean it down but I have heard the other way also. What really happens when you run a ported MAF? Since you are getting more airflow is it leaning down? I thought I read something a while back where when you have a ported MAF since the hole is bigger then the air doesn't hit the wires as fast thus causing the pcm to thing that there is not as much air coming through. I searched but couldn't find it. What is really happening when you port the housings out?
Tech Contributor
Joined: Dec 1999
Posts: 32,910
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From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
I have heard that it will lean it down but I have heard the other way also. What really happens when you run a ported MAF? Since you are getting more airflow is it leaning down? I thought I read something a while back where when you have a ported MAF since the hole is bigger then the air doesn't hit the wires as fast thus causing the pcm to thing that there is not as much air coming through. I searched but couldn't find it. What is really happening when you port the housings out?
The only way to really know how the change in the MAF is effecting your PCM and engine performance is to look at your LTFTs and log with a wide band!
When you mess with the MAF, you change the MAF air flow calibration. Sure it will flow more air at WOT but your part throttle cruising will be effected even more and thats where you spend 90% of your driving. Most of the time you will loose fuel economy if you don't recalibrate your MAF table. Been there, done that. The seat of the pants on a stock engine is minimal.
BC
Thread Starter
Melting Slicks
Joined: May 2005
Posts: 3,394
Likes: 12
From: Leon Iowa
St. Jude Donor '06-'07-'08-'09
Hmm, well i have had a ported one on my vette for a long time. I just have boltons on the vette. Well today I put it on my Trans am, It runs rich because of the cam and other things. I took it for a drive and it almost seemed to run better. It didn't seem to buck at slow speeds. I didn't really notice much at WOT. I know the tune isn't right on the ta so I'm wondering if the ported MAF leaned it out some thus making it run better?
Le Mans Master
Joined: Aug 2005
Posts: 5,375
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From: CA.
St. Jude Donor '13-'14-'15
Putting a ported MAF on my 98 made the LTFT's run 18% rich at most of the part throttle positons and about 12% at WOT---Depending on the air filter setup and other airflow characeristics like removing the screen it can go either way--Like Bill says the only way to make sure is to log the LTFT's and/or use a wideband
Le Mans Master
Joined: Nov 2003
Posts: 8,004
Likes: 250
From: Tampa Fl
St. Jude Donor '12-'13-'14
According to engine management advanced tuning book:
Porting your MAF will skew the output downward by 7 to 10%. The lower calculated loads both leans out the fuel and advances timing running the risk of premature knock.
For the last year, I have switched back and forth between screened and unscreened. Friday, I put my screened MAF back in the car and I wont change it back
Porting your MAF will skew the output downward by 7 to 10%. The lower calculated loads both leans out the fuel and advances timing running the risk of premature knock.
For the last year, I have switched back and forth between screened and unscreened. Friday, I put my screened MAF back in the car and I wont change it back
Le Mans Master
Joined: Jan 2001
Posts: 5,786
Likes: 6
From: Lafayette Colorado
If you running richer with a 'ported' MAF from a stock MAF, you have LESS airflow. If the portign is doing right, there should be more airflow than expected and the LTFT should be positive indicating a lean condition. Unless you really know how to port and tune a MAF, leave it alone!
Keith
Keith
