MAF sensor in relation to IAT mod ... - Fuelly Forums

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Old 03-30-2007, 11:44 PM   #1
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MAF sensor in relation to IAT mod ...

Hello -

I just found this :

Getting The Flow Of MAF Sensors
http://www.wellsmfgcorp.com/pdf/Counterpoint3_2.pdf
Quote:
There are two basic varieties of MAF sensors: hot-wire and hot-film. Unlike vane air flow (VAF) sensors that have a mechanical spring-loaded flap to measure air flow, MAF sensors have no moving parts. Instead, they use a heated sensing element to measure air flow.

In a hot-wire MAF, a platinum wire is heated 212 degrees F above the incoming air temperature. In a hot-film MAF, a foil grid is heated 167 degrees F above ambient air temperature. As air flows past the sensing element, it has a cooling effect. This increases the current needed to keep the sensing element
at a constant temperature. The cooling effect varies directly with the temperature, density and humidity of the incoming air, so the current change is proportional to the air ?mass? entering the engine.
Let's say that all that is exactly true for my car. In the hot-wire MAF + the IAT mod (a resistor instead of a sensor to make the ECU/PCM think the outside air is like Death Valley or something), the MAF wire would be heated to 212 degrees F + the fake IAT input. Soooo, the MAF sensor would be operating at a much higher temperature than it is supposed to run in relation to the air temperature that is actually entering the engine. Since the difference in temperature is greater, the MAF sensor would be cooled to a greater degree by the incoming air. To keep the MAF sensor at 212 degrees F above the fake IAT temperature, the ECU/PCM would increase the voltage more than it would for normal IAT.

Does this make sense?

Question : What would the increase in voltage mean from a temperature, density and humidity POV? Would the ECU/PCM think it's in a "humid muggy environment" (humid air maybe having a greater cooling effect)?

CarloSW2
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