Combustion engines burn petrol or diesel to increase the temperature and therefore the pressure in the combustion chamber, which generates the force to push the pistons down. The more fuel you burn, the higher the temperature and the bigger the pressure.
To burn 1 kg of petrol, you need 14,7 kg of air. If the ratio is right, you can burn the petrol completely. If you have too much air, Nitrogen from the air will burn to NO and NO2. If there is a lack of oxygen, the petrol will not burn entirely, causing CO, HC and soot. If the mixture is much to lean or too rich, it will not ignite at all.
To burn the fuel completely, it is essential to mix exactly the right amount of petrol to the amount air. Therefore, to determine the right amount of petrol, the motor management has to know the amount of air the engine inhales. Some engines use a throttle position sensor and a Manifold Air Pressure sensor to calculate the airflow, other use an air mass meter to measure the flow.
Diesel engines do not have a throttle, so they always inhale the full amount of air. Diesel fuel is unstable; it will ignite spontaneously when injected in the hot, compressed air inside the engine, even if there's a large surplus of air. It would therefore seem unnecessary to measure the amount of air going in. Nowadays, however, diesels use Exhaust Gas Recirculation to reduce NO and NO2. To determine the amount of EGR and the remaining oxygen in the engine, modern diesel engines are also equipped with air mass meters.
Air mass meters come in three varieties: vane meters, hot wire meters and hot film meters. The vane type is a valve, which is pushed open against a spring force by the resistance of the airflow. Therefore, the opening stroke of the vane is a measure for the airflow. Hot wire and hot film meters measure the amount of electrical current needed to retain a certain temperature. The more air that flows by, the more the wire or film will cool down and the more current it takes to restore the temperature. The current is an indicator for the amount of air.
Emission failures in the engines EOBD fault storage memory are often caused by incorrect mixture. The air mass meter is a well-known suspect and will have to be replaced if faulty. To prevent new failures, it is essential that the new air mass meter works accurately, according to the same characteristics as the OE air mass meter.
Nipparts offers a wide range of high quality air mass meters for Japanese and Korean cars. Nipparts air mass meters are made to OE specifications and OE matching quality to ensure a perfect fit, easy installation, flawless operation and maximum durability.
Nipparts air mass meters
- High accuracy for exact air mass determination
- Perfect fit
- OE matching quality
- Tuned to OE characteristics