MAF Sensor off-car

Using the table above we can figure out which pin is used what and also with out risk of damaging the sensor.

Mass Air Flow Sensor:

- This sensor is used to calaculate the mass(amount) of air entering the EFI intake manifold and thus entering the engine also added fuel on the intake stroke to be compressed and ignited . It is very important specialy on vehicles that use turbo chargers or are used in altitude. This sensor does this by metering the amount of air entering the intake manifold before Throttle butterfly so it can calculate how much air exctly entering the engine and send it back ECU via signal voltage. ECU can use this info and various other sensors inputs to choose the best map on this memory for emmisions and also performance of the vehicle .

- There are two main types : Vane type and Hotwire

Vane type : it has a vane or flap on the intake air pipe and it opens as air flow increases and closes as the air flow decreases . One of the major drawbacks is they are not very accurate specialy with quick increase throttle(accelerateing) will cause it open due to the sudden increase of vacuum in the manifold but then it slowly adjusts to its correct position. Also when quickly decelerating it causes the flap to completely close and not let any air to go past but this issue is over come with Idle air contorol unit. This sensor has carbon tracks with wipers which will change the output voltage according to how far has the flap has been opened.

Hot wire : This air flow meter is more accurate because it calculates how much air and even the density of the air passing it (dense air is cooler so it will cool the hotwire down even more . It does this by using a very simple principal which is the more air passes a hot object it will cool it down depending on the valume of air passing it. It has a "Hot wire" which will heat up to a very temp and as the wire is hot so there is more resistance and more resistance means more voltage drop therefore lower voltage sent back to the ECU ... As air rushes pass the hotwire it will cool it down and this will drop the resistance of the wire , less resistance means less voltage drop therefor higher voltage is sent back back to the ECU.

Th voltage output of this sensor proportional with the amount of air passing the sensor(hotwire) . We powered on the sensor by giving it battery voltage and also supplying it with a 5Volts reference which comes from the ECU to the sensor also a ground and signal wire which sends the output voltage from the sensor to the ECU . After sensor was powered on it gave us around 1.137 Volts but when we increased the airflow it gave us around 2.8 Volts .... The manufacturer spec was 1-5 Volts which shows that sensor is working properly.