att Loc. (And gene of course)

SOBIL · rice boy Joined: 09 Jan 2003 Posts: 43

Mass Air Flow? Sorry i don't quite get what is being measured? I was under the understanding that it messured rate of flow, which put with the crosectional area of the meter was basically messuring volume of air. Please explain what is really happening. thankzzzzzzz.zzzz

TXcoupe · petrol head Joined: 05 Oct 2001 Posts: 1675

it measure the air velocity and temp of the air i guess

Gene FJ20DET · Posted: Fri Apr 25, 2003 8:22 pm Post subject: Re: att Loc. (And gene of course)

im not technical enuff for that. Smile

lol

look---->
a blue car
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DrIFtA · tinkerer Joined: 13 Mar 2003 Posts: 246

Bassically spot on TXcoupe, it measures the flow rate (velocity) and in some odd variations also measures the incoming air temp. It's yet another one of the quadrabillion sensors that measures a particular part of the engines efficiency and sends the info to the computer. The comp then (also wit da help of da O2 sensor and most of the others TPS, etc.) sends the right amount of voltage to the injectors for the desired amount of fuel to be added. There is a fine piece of wire inside the MAF that has a constant amount of voltage running through it, when air passes over the wire it gets cooler, so more voltage is added to it to get it back to norm. The comp reads how much more voltage needs to be added to get it back to norm then determines that there must be X amount of air passing over it to cause X amount of voltage drop.
The cross-sectional doolacky that you wrote about bassically works both as a type of filter for the MAF wire, and to regulate or make the flow being read a little more consistant.
It very rarely ever measures the ambiant temp of the air, the two main temp sensors are (obviously) the radiator coolant, and the O2 sensor that measures heat in the exhaust to determine wether your running too rich or too lean. Put it this way, imagine running the engine at full song in the Antarctic, inlet air would be the brass monkey variety. Then imagine it running at full song in Kalgoolie - hot as a mother bitch. This would cool the MAF wire at differing rates, therefore it'd add or reduce injector pulses making it run inconsistent.
The MAF is a more accurate (reads quicker as well) device than a MAP sensor, but in high HP applications it can pose a problem to restricting inlet flow.

Loz · backyard mechanic Joined: 05 Oct 2001 Posts: 943

Yes.. that.