Porting MAF, does it run rich or lean?
07-05-2007, 01:28 PM
#1
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?
07-05-2007, 01:37 PM
#2
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i dont recommend you port your MAF. just not a good deal. it can make your car run bad, make it hard to tune, ect. if your wanting to run a bigger MAF just run one out of a corvette. I forget what years have the bigger MAF's, (85mm) maybe all corvettes, but its a better idea and will only take a few minutes of searching to fine the answer. just my opinion.
Jon
but to answer your question, when you port a MAF, since its getting more air, i would think the PCM would compensate by dumping more fuel, making you run rich. but since you can fugg some **** up by porting your MAF who knows what the PCM would do.
Jon
but to answer your question, when you port a MAF, since its getting more air, i would think the PCM would compensate by dumping more fuel, making you run rich. but since you can fugg some **** up by porting your MAF who knows what the PCM would do.
07-05-2007, 01:46 PM
#3
well I have ran a ported MAF on my vette for a long time. It just has boltons and such. Today I put it on my trans am to see how it would run. My ta has cam and other things thus making it run rich. Honestly it seemed to make the ta run better on the low end. Less bucking but couldn't really feel much on the top end. Makes me wonder what is going on.
07-05-2007, 04:07 PM
#4
It will run lean. I have seen this many times on customer cars that were tuned, but they wanted more airflow. They installed or ported/descreened their MAFs and the wideband now showed it was lean. One case was by 25%! 
The reason for this is because the opening is now much larger, allowing more airflow to enter the engine, plus the airflow is much slower then OE. This slower airflow does not cool off the heating element (used by the ECM to decipher airflow volume), causing the ECM to think there is not as much air going into the engine, thus calculating it need less fuel to maintain stoich (14.63).
If you want to run a bigger MAF or port yours or modify it in any way, that is fine, so long as you get the MAF Table retuned for the changes. Do not just modify it and forget it, do it right and get it retuned.
The reason for this is because the opening is now much larger, allowing more airflow to enter the engine, plus the airflow is much slower then OE. This slower airflow does not cool off the heating element (used by the ECM to decipher airflow volume), causing the ECM to think there is not as much air going into the engine, thus calculating it need less fuel to maintain stoich (14.63).If you want to run a bigger MAF or port yours or modify it in any way, that is fine, so long as you get the MAF Table retuned for the changes. Do not just modify it and forget it, do it right and get it retuned.