Only a change to high flow filter affected MAF calibration?

[blackbolt22]

Hello all. I am wondering if someone can provide information regarding why this occured.

I made some 3rd gear pulls and datalogged them. Changing ONLY from the OEM paper filter to a new Synthaflow skewed my STFT by +3% more fuel and interestingly enough showed a LOWER lbs/min on the MAF flow across the rpm range vs. with the OEM filter by that same amount. Correcting the MAF lbs/min +3% since fueling was +3% brought the MAF lbs/min up to a little higher than OEM filter datalogs which is what I expected.

My question is why doesn't the MAF just meter more air flow with the better filter? It must be because the velocity of air is slower with a less restrictive filter?


Why is this exactly? Why couldn't I drop in a better filter and the MAF just simply see more air without skewing the calibration? Is it because the restriction is lower with the Synthaflow which slowed the velocity of air per lbs? This is what I think but I need a confirmation

[decipha]

prob just the dirty filter

for a real test try using a clean paper filter