The air mass flow sensor (MRF or MAF) is one of the key devices for collecting telemetry data from a modern car. It can be described without exaggeration as the main sensor from which the ratio of petrol or diesel fuel composition depends on the fuel-air mixture. How the DIA signal is used

How the DIA signal is used

The signal received from the sensor is used by the electronic engine control unit. Its signal, combined with signals from other sensors, for example, the lambda probe, is converted to digital data to calculate the amount of fuel that is to be put into the combustion chamber in order to obtain the so-called stoichiometric ratio of petrol and air during engine operation under a certain load.

No other sensor on the engine can boast such a wealth of names: MAF, MRI, flowmeter ...

The air mass flow sensor is an important component of the distributed injection system. The start of its mass application coincides with the advent of low-cost microprocessors on the electronics market. General Motors (GM) has become the first car company to use a heat sensor on the basis of a heated wire.

The computer program of the injection system began to appear in serial cars at the beginning of the eighties, and the mass flow sensor appeared with them. Mass Airflow Sensor-English translation of mass airflow meter, MAF. In the copiroammeter, in terms of "flowmeter", amateur auto-amateurs are most likely to be in the form of an MRI.

Mass flow sensor device

In world practice, a number of MRI have been used at different times. However, the most common construction in our time is an MRI on the basis of heating wire. The other type is a fairly common type-flow-meter based on the flügering ground.

Wire wire sensor

The sensor element is set in the middle of the inlet to the inlet to the air inlet. Sensitive sensor element-two thin platinum filaments for which electric shocks are applied after ignition. The effects of the electricity on the thread are heated. When the air is in the air, the threads are cooled and their resistance changes. The engine control unit monitors changes in the resistance and interprets them as a signal to reduce or increase the flow of air.

Some modern air mass flow sensors are equipped with an electronic self-cleaning system

Advantages of the sensor on the basis of a heated wire compared to the dmrw on the basis of a fluorine oil, the rapid reaction to changes in the air flow; does not create obstacles to air flow; there are small dimensions; there are no moving parts, below the cost; the sensor measures the mass of the passing air, not the volume (which is important according to the theory of the ideal fuel mixture).

Disadvantages: The sensor is highly susceptible to contamination.

Flugorn bulk air mass flow sensor

This type of sensor was often used at the end of the eighties-early nineties at a time when the most common system of electro-managed injection was monopnod. The sensor element was the intake manifold in the intake manifold. Passing through the flap, the flow of air opens it. A potentiometer is installed on the shale axis, changing the resistance in proportion to the angle of rotation of the cap.

In winter, every engine without exception becomes a little bit more powerful as the density of the cold air increases, and the total air flow falling into the engine becomes slightly heavier

Sometimes the sensor is equipped with a adjusting screw for the manual configuration of the fuel-air mixture. The configuration allowed part of the stream to pass by. Thus, it was possible to continue measuring the dynamic parameters of the air flow, which partially impoveres or enriches the mixture depending on the average temperature of the air in the region, the height above sea level and the tp.

In comparison with modern wire dvrv, the sensor with a salon has a number of drawbacks:

The cap limits the flow of air, thereby reducing the engine power;

The accuracy of the measurements depends on the wear of the moving mechanical parts and the potentiometer contacts;

for complexity, the cost is higher.

The common design of the sensors is a protective grid to smooth the flow of air.

DIA alternative designs

In some vehicles, GM vehicles are used on the basis of "cold wire". These sensors measure the self-induction of a sensitive element arising from contact with an airflow.

The flowmeters are based on the phenomenon of the collapse of the vortex. The principle of action is based on Theodore von Karman's theoretical physics theory. This type of sensor is designed to measure the frequency of disruption to the vortex forming the so-called "Karmana track". According to the theory, the frequency of the breakdown is directly proportional to the speed of the flow.

The most common modern MRI is a heated wire sensor

Membrane flow-meter. Ultra-modern design based on the use of the finest membrane in the air flow. Temperature sensors are installed in the leeward and windward sides. The windward and windward side of the vehicle are not cooled during the movement of the vehicle. It is this difference that the control unit is evaluating.

DIA operational issues

In most cases, today's dmrh sensors are out of service at a high mileage or use of a car in harsh climatic conditions, especially if the air is heavily contaminated with dust or dirt particles. In the event of a deviation from the air filter replacement procedure, the dirt penetrates the sensor enclosure and settles on the threads. It is this fact that often causes the "failure" of the sensor, even though it needs to be cleaned and reestablished in full.

Even with the timely replacement of air filter, the sensitive element of the MRI requires periodic cleaning

Constructors have found a way to eliminate minor contamination that does not require human intervention. Most sensors have a special relay, which after ignition is turned on, takes a few fractions of a second to absorb the high voltage current probe threads. If they have organic structures, they can just burn or evaporate. Unfortunately, with significant pollution, the self-cleaning system is powerless.

When the sensor fails, the engine control unit goes into an emergency mode that does not allow high speed. The engine malfunction detector "check engine" shall be detected on the instrument panel. You can determine the health of the sensor by measuring the resistance in the connector or by connecting the computer diagnostic scanner to the computer. If there is resistance, the sensor threads are likely to be targets, and you can try to clear them with a special tool, and if you don't have it, you can use a carburetor cleaner and a small cotton swab. It is not recommended to touch the electronic components of the sensor.




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