I had a ported MAF sensor which made the car run lean at WOT so i put in a BONE stock sensor and now my gas milage is down about 30+ miles to the tank but there is no ses light and in closed loop the AFR wouldnt be effected by the condition of the maf sensor as it tries to get 14.7 regardless.... I was going to run datamaster if someone could give me an idea what to look at to see if there is a problem, I am guessing a low BLM?

 

ported MAF sensors totaly screw up the calibration/ basically its innacurate. if the ported MAF made your WOT lean and the unported MAF doesnt.....well there is your 30 miles of gas.

I make 431 RWHP with a STOCK unported ( descreened tho ) MAF

I tried using a ported MAF but i couldnt tune the car correctly. the ported MAFs are worthless.

If you can tune your car just tune it with a stock MAF

 

not sure what you mean, since even ported the computer would use the o2 sensors to adjust the AFR to be 14.7, which leaves me somewhat confused unless im just wrong

 

I got sucked into the ported MAF craze a couple years ago Unfortunately something happened to the elements within the sensor at some point during the porting and caused my car to run very rich. I did take the MAF appart to port it too. There was no obvious signs of damage nor an SES light but hooking up a scanner showed me that my BLMs or fuel trims were bottomed out at 108 on both banks. This meant the MAF was reading more air than was actually entering the motor. It was so bad in fact that the computer couldnt even fully compensate for it so my car basically ran rich all the time. I never put the car on a dyno with a wideband to check out AFR so I cant tell you if it was running lean like yours is. What I can tell you is that your probably busted your MAF like I did with mine... that expains your decrease in gas mileage.

 

if you ever look at a ported MAF next to a STOCK MAF you will see that it splits the AIR intake into 2 chambers. 1 side measures an amount and the other side uses different elements to measure the amount. If you port the MAF it ruins the calibration completely.

The PCM uses the O2 sensors feedback but it also uses the MAF to calculate initial A/F . SO the ported MAF sensor causes teh PCM to add more fuel at an idle then your O2's say the car is RICH and your BLMS go off teh chart trying to compensate. Your PCM also uses these BLMs at WOT. It takes the last corerction factor and uses that number when you go to WOT to add into the fuel algorithm.

Please Trust us, you are not gaining anything with the ported MAF, other than a massive headache trying to fix your tuning.

I went to a STOCK MAF and GAINED HP over my ported MAF, not to mention I spent a month of headaches trying to figure out why my cars A/F was always screwed up and the ported MAF housing went into the garbage.

 

I would imagine the original problem of running lean would cause you to lose gas mileage now that its richer.

Hal

 

Hey guys I said I put a stock maf sensor back on the car I dont have the ported maf anymore because it was inaccurate like you said.... please re-read my post because i think you could help me if you know the sorts of things you guys were talking about... Basically I was asking why my fuel milage went down when I swapped back to my stock maf? Was the ported maf making it run lean even in closed loop mode ALL the time because now I can barely get 200 miles to a full tank around town so maybe it was running right before and now its rich for some reason, I have no Idea....

 

maybe the stock MAF is broke. only way to tell w/o getting error codes is using a scanner.

 

use the MAF sensor that you were using before, but just put the STOCK MAF ENDS onto it. Not all MAFs are the same. For example, I tried to use a MAF from a 95 Z28 and my car would hardly run. put my ported MAF back in with the STOCK ends and it works great.

 

So maybe my maf is not really right for my car.... so if it wasnt right for the car what would I need to look for when using datamaster. If I know that maybe I can swap maf ends and see the difference... Thanks again guys!

 

im not sure how to tell, because i looked at my scan tool trying to figure out what was wrong with my car. the MAF reading looked fine, but as soon as i put my origional MAF in it cured the problem.

Porting the ACTUAL MAF itself doesnt hurt the calibration, its when u port the MAF ends that throws off the calibration.

 

Gotcha! Ill try that and see what happens... Thanks again guys.