What exactly are the MAF's? - The Unofficial BMW M5 Messageboard (m5board.com)

M5BHP · 2nd March 2005, 16:12

What exactly are the MAF's?

I hear ppl talking about them but I haven't got a clue what they are.

DIPLOMAT · 2nd March 2005, 16:32

Mass Air Flow Sensors, they basically calculate the amount of air coming into the engine to accurately match the amount of gas. if you pop open your hood you will see a plug on each intake and those are your MAFs

M5BHP · 2nd March 2005, 16:58

thanks

Quote:

Originally Posted by DIPLOMAT

Mass Air Flow Sensors, they basically calculate the amount of air coming into the engine to accurately match the amount of gas. if you pop open your hood you will see a plug on each intake and those are your MAFs

Carrera2RS · 3rd March 2005, 00:15

Mass air flow sensors measures the mass of air coming into the engine via a hot air film system or flap valve (not sure on the M5, I suspect a hot air film basis)

The engine management system then looks at the rpm and delivers the appropriate amount of fuel, via a programmed map. The advantages of mapping an engine (setting the fuelling) via these inputs is that the MAF sensor is self regulating to a degree - If the air is hot, the mass is less therefore less fuel, if the air pressure is less the mass is less therefore less fuel, etc

Race engines are mapped via throttle position and rpm with adjustments for air temp and pressure, this is much more responsive but not as emission friendly !

de Witt · 3rd March 2005, 00:32

Quote:

Originally Posted by Carrera2RS

Mass air flow sensors measures the mass of air coming into the engine via a hot air film system or flap valve (not sure on the M5, I suspect a hot air film basis)

The engine management system then looks at the rpm and delivers the appropriate amount of fuel, via a programmed map. The advantages of mapping an engine (setting the fuelling) via these inputs is that the MAF sensor is self regulating to a degree - If the air is hot, the mass is less therefore less fuel, if the air pressure is less the mass is less therefore less fuel, etc

Race engines are mapped via throttle position and rpm with adjustments for air temp and pressure, this is much more responsive but not as emission friendly !

I would be hesitant to call the MAF self-regulating. It takes instantanous measurements of air mass and sends a signal to the computer based upon the voltage resistance measured at the wire. The MAF does not deliver feedback to regulate itself, the computer does all of the regulating work. The MAF cannot sense conditions that you describe, but it does send a signal to the computer that will regulate the injector pulse width. The MAF wont change anything to itself, but it will change the pulse width.