DOES THE MAF SENSOR READ CORRECTLY IF MOUNTED BACKWARDS (REVERSING THE AIRFLOW) ?? LOGICALLY IT SHOULD, BUT DOES ANYONE KNOW ?? (86 TPI WITH BOSCH SENSOR)

 

TA,

The MAF should not read correctly if it is installed backward. The sampling tube in the sensor body contains a hot wire element and two temperature sensors. The sampling temperature sensor must be upstream of the hot wire, or its reading will be skewed by the heat generated by the hot wire element. The discharge temperature sensor must be mounted downstream of the hot wire to measure air temperature after the hot wire element.

The MAF works by sampling the incoming air temperature. The electronics package compares the incoming air temperature to the exit air temperature, and varies the current through the hot wire to maintain a constant 75°C differential. The amount of current required to maintain the temperature differential is closely measured, and this is the basis for the air flow measurement. In other words, the amount of heat radiated to the air passing through the sensor is the metric for determining the amount of air passing through the sensor.

Since the temperature, humidity, or density of the incoming air will change the number of air molecules in a standard volume of air, the volume of air does not directly relate to the number of air molecules. The molecules of air passing through the sensor are what remove the heat from the hot wire, and the number of air molecules (or actual mass of air, not volume) are what is measured. This is a constant, regardless of humidity, temperature, pressure, and barometric pressure changes, so the sensor automatically compensates for these changes.

However, for this to occur, the temperature sensors must be arranged correctly in the air stream. The large arrow on the sensor body indicates the correct flow direction.

 

That post brought to you by Vader. Author of the book "More than you ever wanted to know about your MAF sensor"

JK that was a great reply Vader

Hodge

 

THANK YOU MR. VADER FOR THE REPLY.
I WAS LOOKING AT SOME OF THE HOME MADE COLD AIR INTAKES AND ONE HAD A PICTURE SHOWING THE 45 DEGREE ELBOW ON THE SIDE TOWARD THE ENGINE. THE INSTRUCTIONS DID NOT SAY TO REMOVE AND REVERSE IT. SO EITHER A MISTAKE, OR SOME MAY HAVE THE ELBOW ON THE ENGINE SIDE SINCE MINE IS ON THE AIR FILTER SIDE.