[MKJS]

Does anyone know off the top of their head,

1. Does the MAF sensor try and maintain a constant temperature? If so, what temperature does the MAF wire try and maintain?

2. Is the MAF constant temp compared to atmospheric temp?

3. If 2 is true, does it base it's calculation on the temp received from the OAT sensor under the front Right fender.

4. Or does it use a cold wire? Or some other means of finding OAT.

Thanks in advance,

Jim

 

[TheAngryBear]

AFAIK The MAF should be taking in a constant voltage. It then heats the wire/film and based off the cooling from the wire/film the voltage through the system changes. That signal is then translated to the air mass.

I don't think it is connected to the ambient temp sensor but in some models is connected to the barometric pressure monitor.

 

[MKJS]

Let me see if I have it, the maf receives a constant voltage, then knows what temperature that voltage should produce? If I have that right, how does the maf know what temperature the applied voltage produces? Or perhaps it reads the voltage coming out of the maf after it reaches some temp????

Thanks,
Jim

 

[TheAngryBear]

Let me try a different way: The voltage input to the MAF is constant. This heats the film/wire that is the measuring part of the MAF. This heat creates resistance dropping the output voltage. As air flow (mass) increases the resistor cools in temperature thus raising output voltage. The output voltage is translated to the air mass for calculations.

 

[MKJS]

Got it, well put, thanks.

Delta A = V
T

Where:
A = Amperage
T = Time
V = volume of air

 

[mattmar1]

if i understand maf operation correctly, while the voltage remains constant the dme drives the current to maintain a constant temp on the heated film, to amount of additional current required extrapolates to the mass of air flow thru the maf, with the intake air temp being a factor. anyone please correct me here if im mistaken. there are two wires in the maf, one heated,one unheated, and both are monitored by the dme.

 

[TheAngryBear]

if i understand maf operation correctly, while the voltage remains constant the dme drives the current to maintain a constant temp on the heated film, to amount of additional current required extrapolates to the mass of air flow thru the maf, with the intake air temp being a factor. anyone please correct me here if im mistaken. there are two wires in the maf, one heated,one unheated, and both are monitored by the dme.

That could be. I thought the nonheated was the "reference" wire to get the delta. Sorta like a wetbulb and dry for humidity.

 

[rdl]

Try this link for an MAF primer.
https://en.wikipedia.org/wiki/Mass_flow_sensor
The section on hot wire & hot film applies

And attached PDF pages 14 & 15 for BMW details, at least the M54

 

[TheAngryBear]

Try this link for an MAF primer.
https://en.wikipedia.org/wiki/Mass_flow_sensor
The section on hot wire & hot film applies

And attached PDF pages 14 & 15 for BMW details, at least the M54

Awesome info and thanks! Looks like a little of everything we stated.

 

[MKJS]

Try this link for an MAF primer.
https://en.wikipedia.org/wiki/Mass_flow_sensor
The section on hot wire & hot film applies

And attached PDF pages 14 & 15 for BMW details, at least the M54

Excellent info thank you!!

Jim

 

[mjayc]

Does anybody know how many G/s a good working MAF should be at idle?

 

[TheAngryBear]

Does anybody know how many G/s a good working MAF should be at idle?

MAF for what model? There are some reference values for a 540 but you are showing 530. So might not be applicable.
http://www.bimmerfest.com/forums/showthread.php?t=910726

 

[mattmar1]

Does anybody know how many G/s a good working MAF should be at idle?

i can read my 528 tomorrow when i get a moment, but its not a 530 so there will be some variance