Not all mass airflow sensors are the same. A vast array of MAFs are available for all types of vehicles – and this is what you need to know.
The 1980s saw the introduction of the personal computer, big hair bands – and the mass air flow sensor (MAF). During the decade of excess, the MAF proliferated as fuel injection began to replace the archaic carburetor.
These days, nearly all vehicles use a MAF to measure the volume and density of air entering an engine. Data collected from the sensor is used by the engine control module (ECM) to determine how much fuel the vehicle needs.
Not all MAFs are alike
Most modern vehicles are equipped with either a hot-wire or hot-film MAF sensor. Both designs operate in the same manner; incoming air cools the heated element, thereby changing its resistance.
As the resistance changes, the amount of current needed to keep the sensor hot also changes. The ECM uses this variation to determine how much air is entering the engine. Sometimes intake air temperature is also calculated this way, eliminating the need for a separate IAT sensor.
Many older German vehicles have a different kind of MAF called a vane airflow meter. Instead of a heated element, the design uses a spring-loaded flap to determine the volume of air entering the engine. A sensor measures how much the flap is open, and that data is interpreted by the ECM.
MAF designs vary a great deal depending on the year, make and model of the vehicle. The discrepancy is obvious when comparing a handful of common sensors.
Three generations of BMW MAFs
BMW MAF sensors are typically made by automotive parts supplier, Bosch. Over the years, a variety of designs have been used in the company’s vehicles.
Bosch 0280202203 This MAF is found on many older BMW cars. The sensor, which uses hot wire technology, is factory equipment on select E36, E30, and E34 models.
Bosch 0928400529 Fewer parts lead to lowered cost and reduced complexity. BMW and Bosch realized that when they introduced yet another MAF in E46, E60, E90, E65 and E81 vehicles. Unlike the units that came before it, this hotfilm sensor measures both intake airflow and temperature. So, there’s no need for a separate intake air temperature sensor.
A Mercedes MAF thrown in for good measure
BMW can’t get all the glory. Mercedes also has a wide range of MAF sensors that deserve attention.
VDO 5WK97917 Much like BMW, Mercedes tends to favor hot-film MAFs. One such sensor is a commonplace 5WK97917 made by supplier, VDO. The component is installed on everything from the refined C-Class to the rugged Sprinter. Both intake airflow and intake air temperature are calculated via the MAF.
Don’t judge a sensor by its cover
What’s the point of all this MAF talk? To remind you, the consumer, how wildly different sensors can be. Make sure you select the right part for your vehicle when placing an order.