An air flow meter isn’t a thing that you buy every day. Therefore it is sometimes difficult to know, which describes the product best. 

First there are many names for our parts, but they actually mean exactly the same part.

Some clients find ‘air flow meter‘ easier to pronounce than ‘air mass meter‘, which is certainly one of the reasons why we are often asked for air flow meters. Very common is also Air Flow Sensor. But there are other names as well like Mass air flow sensor or mass air flow meter or hot film air flow meter or mass airflow sensor or MAF sensor and much more.

We would like to give you a quick overview of the different “generations” of Bosch air flow meters.
With VDO, who is also a original equipment manufacturer for BMW and Mercedes, it is a different story.

Air flow meter
MAF LMM-5 for Opel and Alfa Romeo from years 1971 - 1998

The Aluminium ages of MAF

In the early days the air flow meter would like this. A heavy aluminium housing with the technology build on top of it. This solid part weights approx. 1.2 kg.

The broken part even had to be sent in before you could get a new one.

LMM by the way stand for the German term “Luftmengenmesser” meaning “Air mass meter”. You know, we Germans have a weakness for long words;)


Hotfilm and plastic

From the late 80ties Bosch changed to plastic housings with a “finger” could be removed by torx bits. The “finger” holds the technology which is now no longer hot wire, but hot film technology. The plug was usually round with 4 or 6 pins. The part was already lighter, but would still weight between 400 to 700 grams.

But not only the housing changed. Also the technology was improved and first used in Formel 1 vehicles!
The short code “HFM” stands for Hot Film Meter or “Heissfilmluftmassenmesser” in German. In our other blog article we describe what exactly this means.

MAF sensor fits Mercedes Benz
MAF HFM-2C-4.7 for Mercedes from years 1992 - 2000
Maf sensor hfm-7
MAF HFM-7-CI0 for BMW from years 2003 - 2011

Welcome in the 20th century, MAF

In 2002, Bosch, for the first time,  launched HFM6, a mass airflow sensor with a digital signal.

The first generations of air flow meters, whether hot-wire air flow meters (HLM/LMM5) or hot-film air flow meters (HFM), still delivered the load signal in analogic form. The 6th generation, however, is digital for the first time.

In the HFM 6, the air mass is not transmitted to the control unit in the form of a voltage, but as a variable frequency depending on the air mass.

This MAF already weighs only 280 grams and less weight means less gasoline consumption.

MAF HFM-6-ID for BMW from years 2006 - 2012

The next generation HFM 8 – with humidity sensor

Car manufacturers demanded a more precision from the developers of air flow meters. So that the stricter emission and consumption laws are being met. Well, ok, probably did the Diesel affaire now popped into your mind, but let’s not talk about that.
Anyhow Bosch developed the HFM8 with a much more sophisticated technology which includes a humidity sensor or to be more precisely a heated sensor membrane over which the air flows. 
But to get more information about this top of the edge technology, please visit directly the Bosch website Mobility Solutions.