Automobiles, Cars
Air flow meter. Air flow sensor
In order for the engine to operate reliably in all modes, it is necessary that it obtains the optimal composition of the fuel mixture. As you know, fuel alone is not enough for the engine, it also needs air. In different modes of the engine requires a different ratio of oxygen and gasoline. The air mass flow meter is responsible for this.
What it is?
This is a mass air flow sensor. It determines the amount of oxygen that is needed to fill the engine's engine cylinders under various operating conditions. Installed this device in the intake tract. You can find it after the air filter, in the inlet pipe, or on the body of the filter element itself.
How the device works
This sensor is required, as already mentioned, to measure the ideal amount of oxygen that enters the engine. So, DFID calculates the right amount and immediately sends this data to the ECU. He carries out calculations of the necessary amount of fuel.
The stronger the driver presses the accelerator pedal, the more air will enter the combustion chambers of the power unit. The flow sensor immediately captures this, and then sends the command to the host computer to send more fuel to the cylinders.
If the car moves evenly, then in this mode, oxygen is wasted in small volumes, which means that the fuel consumption will not be large. This is followed by this very air flow meter.
Device, types of sensors, operating principles
Together with technical progress, the design of these devices is being improved. At the beginning of the development of the automotive industry, a Pitot tube was used for these purposes. A similar device was also referred to as a scoop air mass meter. A thin plate was used as the main element. It was gently fixed. The air flow bent the plate. The potentiometer, which was also built into the circuit, could measure how strongly the plate was bent (the resistance was measured). This was a signal for the main control unit.
On the same principle, these instruments operated on many German cars. So, if you open the air flow meter "BMW" 80-ies, then you can find a sensor with just such a device. Naturally, on modern cars are systems with another device.
Among the most modern and common on many cars, devices are distinguished by plate metering devices. In this device, a heat exchanger with two platinum plates is used as the base element. With electricity, the plate heats up.
This works as follows. When the airflow passes through the heat exchanger, it cools the working plate from platinum. To maintain the same temperature on this plate as on the control plate, it receives more current. The change in current is the data that the computer needs.
Another air mass meter is a device with film meters. The working elements here are silicon plates with platinum coating. This technology is used recently, so these designs are not yet very common.
Still there are devices with vortex meters. Their work is based on measuring the frequencies of vortices that are created at some distance behind the protrusion in the inlet valve.
The most modern design is a membrane type flowmeter. A very thin membrane is used here, which is placed in the air stream. Temperature sensors are installed on one and the other side . When the car moves, the sides can not cool evenly. The temperature difference is then sent to the ECU for further calculations.
In modern foreign cars, such a sensor may not be present at all, instead of it an absolute pressure system is used.
Symptoms of malfunctions
In the car there is nothing eternal, the sensor of the air flow meter also goes out of order, and regularly. Many motorists are discussing this problem on the forums.
How can you find out that this important device is starting to fail? Very simple. Those indicators that measure this element are very important in the process of the correct preparation of the working mixture of fuel and air. Failures of the DMRV lead to serious malfunctions of the motor, or even the engine can not be started at all.
If the flowmeter is out of order, the lamp on the dashboard, which suggests checking the engine, may catch fire. Also, malfunctions entail an increased fuel consumption, a sharp decline in the power of the power unit. For example, when the "Audi" air mass flow meter breaks down, this is also accompanied by a decrease in the dynamic characteristics of the German car, it becomes very difficult to start the engine, there is no stability of the rpm in idle mode.
An experienced car enthusiast will say that these are standard signs that may not be related to the DMRV in any way. Yes it is. But the first thing to check for such symptoms is the DMRV.
How to check the air mass meter
Modern practice of diagnosis involves the use of several methods of verification.
Then you need to gain momentum to 1500, and then it is recommended to go by car. If the unit began to work much more quickly and more dynamically, then it is the DFID that is to blame for everything.
Diagnostics with the tester
The second method involves the use of a multimeter. Before starting testing, it must be remembered that the method is not relevant for all sensors. In this way, only the Bosch air flow meter can be checked.
The first step is to set the tester to 2 V and put it into the constant voltage mode. In the scheme from "Bosch" it is clearly stated that the DFID must have four wires. So, a yellow signal is applied to the yellow wire, gray-white is voltage, green is ground, pink-black is supplied with the main relay.
Now the red test lead of the tester must be connected to the yellow wire. The black test lead is connected to the green wire. The engine must be silenced before these measurements, but the ignition should not be switched off. The voltage is then measured.
If the element is in working order, the tester will show 101-102. The acceptable reading is 102-103. This is the upper limit, which requires the repair of the air flow meter. If the screen tester is 105 or more, then the sensor is broken, replacement is required.
Visual inspection
The third method involves diagnosing only by external signs. In order to visually diagnose a breakdown, you should carefully examine the internal cavity of the nozzle on which the sensor is fixed. This surface should be as clean and dry as possible.
It should be noted that the most frequent reason why the DFID breaks down is a commonplace dirt that falls on the work site. This often suffers air flow meter "Audi".
To prevent dirt from entering, regular filters should be replaced.
The next step is to remove the sensor. To perform the dismantling, you will need a car key. The two bolts are loosened and the element is removed from the filter housing for oxygen purification.
At the time of dismantling, you need to make sure that there is a polyurethane seal. It is often removed with the sensor. The ring is necessary to protect the system from ejecting. If it is not in the socket, or in the sensor, then the reason is the absence of this ring.
If there is no ring, the dirt will fall into the cavity of the part, which is not considered acceptable.
Repair of air mass meter
In most cases, these devices are not subject to repair. They simply replace with a similar or universal. Repair only those that apply the Pitot tube principle. Often, there are contaminants that can make it difficult to move the plate.
Cope with dirt can be with the help of special sprays, which are used for washing carburettors. In rare cases, you can restore the operation of this variable resistor by setting it to a board with contacts. Sometimes you manage to cope with this problem by simply bending the plates so that the tip works on the still-worn part of the site.
Many specialists at SRT offer disconnecting the device from the ECU block. However, nothing good will come of it.
The thermo-anemometric flowmeters do not respond to repair. But the Bosch air mass flowmeter can be tried to cure.
How to replace the MIRV
If the sensor is not repairable, exit one is a replacement. It is very easy to replace the sensor.
How to extend the resource?
In order for this device to serve faithfully longer, it is necessary to change the air filters in time and constantly monitor the technical state of the engine. To prolong the life of the sensor, it is also possible to repair the engine. Often too worn piston rings and valve seals can lead to premature death of DMRV.
How to clean the MIRV
Clean the sensor is recommended only when platinum spirals are covered with mud.
Before checking the air flow meter, it is desirable to remove and thoroughly wash it. Perhaps this will be a simple solution to the problem, since contacts are often contaminated.
The first thing to do is to dismantle the sensor. Then it is dismantled.
As it turned out, the flowmeter is a very important sensor, and with proper maintenance it will not often fail.
So, we found out what the mass air flow sensor is for.
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