I am not sure how the MAF works, maybe someone can enlighten me... Does it read a volume per unit time then use the IAT sensor to calculate density then density/volumetric flow = mass flow?

So basically, my first question is what does the MAF actually read. And how does it read this. I have another question, but I want to se how this one is answered first.

 

I thought since Nissan uses a "hot wire" system...the wire itself heats up and incoming air cools it to a certain point resulting in the various ECU changes...but after that I'm lost on the subject as far as the technicalities

 

I believe the MAF directly reads temperature drop across a piece of wire due to thermal transfer from the wire to the air flowing through it.

This corresponds to actual mass, which is the ULTIMATE goal of any fuel injection computer's air-related inputs, whether it uses a temperature, pressure sensor or not, computing air MASS is the ULTIMATE goal. So the MAF sensor is nice in that it accomplishes that directly.

 

booyakashaka...

http://www.autoshop101.com/forms/h34.pdf

 

Thanks! You just explained to me why it is that the FSM says that the IAT sensor "is not used directly for engine control" and "is used only for the on-board diagnosis." Whatever that means.

 

Yup. Actually DA-MAX's post was more accurate... the MAF sensor uses an electric feedback circuit between a thermistor (temp. sensor) and the heated wire to report how much current is required to keep the MAF wire at a constant temperature... under the principle that more air mass flowing over the wire cools it down faster.

 

After looking at this, I'll bet you a donut, heck, TWO donuts, that the IAT sensor's function is simply to monitor the health of the thermistor in the maf.

 

this kinda gets into it-->
http://www.autoshop101.com/forms/h32.pdf