But y change it?? Don't understand is it just for more air??
Well you see... Your MUM!
On a serious not, as the turbo get bigger the air that is sucked in increases more and more. Until it reaches a point where the current MAF cannot read the rate of air flow.
Now again, off topic and explain a MAF. All it is, is a heating element where air flows past it, all it does is works out how much the temperature drop is occurring in the current diameter that it sits in and takes into account IAT (intake air temp) & density, does some maths and thats how it works out the air flow. Also when you take the MAF you notice a pug with mesh on it, the mesh is there to smooth (make linear) the airflow to improve reading accuracy.
Back on topic, eventually the MAF reaches its limit due to the way it works as the element can only go so far, so you increase the internal diameter and adjust the ECU to take into account the new area which will effect how it will read the airflow, in short your increasing its maximum airflow range.
Hope this helps
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