AMASSING
POWER EFFICIENTLY
THROUGH QUALITY
BOSCH explains the technology behind air-mass meters and the best practices to
prolong their functioning lifespan.
With emissions, engine and fuel efficiency under close scrutiny today, Hot-wire Air-mass Meters
the air-mass meter is a critical component to the precise performance The wire element within the air-
mass meter is heated by an electrical
resistance from constant current. The
hotter the wire’s temperature gets,
the more electrical resistance there
is within it. As the engine air-flow
passes the wire, the wire cools. This
decreases the electrical resistance and
allows more electrical current to pass
through, to regulate the temperature
of the wire. The electrical current
fluctuation is proportional to the mass of air flowing past the wire. This
is recorded through the electronic circuit and signalled to the ECU.
demanded from the modern engine. The air-mass meter registers
the mass of air that is being drawn into the engine. It then relays
the information to the ECU which uses the measurements to help
calculate the appropriate fuel and air mixture to optimise the vehicle’s
performance and fuel efficiency. In modern diesel applications, the air-
mass meter is also needed to control and monitor the EGR flow rate.
Air-mass meters are also commonly known as:
• Air mass sensors
• Mass Air Flow (MAF) sensors
• Hot-Film air-mass meters (HFMs)
• Air flow sensors
• Air flow meters
WEIGHING UP THE DIFFERENCES
The most common technologies found in modern air mass meters are
the ‘hot-film air-mass meters’ and ‘hot-wire air-mass meters’.
Hot-film Air-mass Meters
This established but developing
technology uses a very thin
electronic film that is placed in the
air stream. Bosch hot-film air-mass
meters are equipped with the
latest technology with integrated
INVEST IN QUALITY
The quality of air-mass meters affects vehicle performance, drivability,
fuel economy and emissions. A poorly made or faulty air-mass meter
can manifest a variety of symptoms such as:
•
•
•
•
Rough idling or stalling
Poor acceleration
Rich mixture at idle or lean under load
Poor fuel economy
Bosch advises to fit complete assemblies when an air-mass meter has
to be replaced. As the precise calibration can be compromised if the
element is removed. The majority of sensor elements and housings are
calibrated to exacting tolerances as complete units.
temper ature, humidity or pressure
sensors and micro electrics. These
sensors have evolved to become
more reliable as they are highly
resistant to contamination.
Bosch air-mass meters are OE products with the performance to match.
Calibrated as complete units in the factory, they achieve exacting
functional accuracy by calibrating the sensor element to the housing
during production.
OE WITHIN REACH
Covering more than 95% of the pareto, Bosch air-mass meters are backed by a 1-year warranty and are available from FPS via same/next-day
delivery. For more information, please speak with your local FPS representative or visit www.boschautoparts.co.uk.
VITAL NEWS ISSUE 47
AIR-MASS METERS 9