Air flow meter or sensor mass flow The air is a device that measures the amount of air entering the engine cylinders. There are several of their varieties that differ in the measurement method. An earlier design is a flow meter with a Pito tube (the so-called blade type). The principle of its work is based on measuring the deviation of the air flow of a special plate, on the axis of which the potentiometer is installed. The device resembles a throttle valve. Depending on the speed of the air flow, the angle of rotation of the plate is changed, and, accordingly, the electrical resistance of the potentiometer.

More modern flow meter designs have a thermoelectric air flow meter. The principle of his work is next. In the air flow there is a heat exchange element in the form of a platinum wire. The stronger the air flow, the more electricity needs to be applied to it to keep the specified temperature difference between the wire and the flowing air. To remove deposits on a platinum wire (diameter of about 0.07 mm), self-cleaning mode is provided, in which after stopping the engine, which operated for a while under load, it briefly heats up to a temperature of 1000-1100 ° C.

The most modern flow meters are thermomemometric with film meter. They have heating and measuring resistors are made in the form of thin platinum layers sprayed on the surface of silicon crystal.

Also there are flow meters with vortex type meters. The principle of their work is based on measuring the frequency of twists, which appear at a certain distance behind the protrusion in the wall of the intake channel. It is worth noting that in many modern foreign cars instead of the air flow meter, an absolute pressure sensor in the intake manifold is used.

Types and causes faulty stey

Each design of the flow meter has its own characteristic faults. For the flow meters of the "blatant" type is the wear of the current-carrying surfaces of potentiometers, the formation of oily sediments on the working elements. The potentiometer wear ("dutiful" of the current-handing track) leads to the periodic disappearance of the electrical signal, as a result, the transfer of distorted data into the control unit. Oil deposits and oxide on the surface of the channel interfere with the movement of the damper (it is subdined). In the case of thermoelectric flow meters, the cause of the malfunction may be the absence of its power from the on-board network of the car, as well as the unqualified maintenance of this node. Even attempts to wipe his work surfaces with cotton can withdraw the flow meter. This node is not served and unrepretentious. You can check only the reliability of the contact connectivity, and in the case of contamination, it can help with compressed air or flushing the working surfaces with special groups.

Diagnostics

The flow meter is located between the air filter and the throttle valve.

In addition to external signs of engine operation, an integrated diagnostic system may report on the malfunction of the air flow meter. Unfortunately, without diagnostic equipment, count the error codes and determine why "shouts" the check engine "Check Engine" is not always possible, so you need to turn to a hundred. Make sure the air flow meter malfunction is possible, replacing it is obviously good. If the result is an improvement - the reason in the flow meter, there is no improvement - you need to search in another direction. Very often, a similar external manifestation provides air seats through compounds or cracks in a corrugated hose, coming from the flow meter to the throttle module.

Methods of repair

Fitting the plate, you can move the slider to the unavailable part of the track.

Most often simply replace a faulty flowmeter new. Maintainable only flow meters with Pito tube ("blade" type). Pollution and oily sediments that interfere with the movement of the plate are removed using

aerosols for cleaning the carburetor. Sometimes it is possible to restore the capacity of the potentiometer, moving it to the board with the contact track or adjusted the plates of the current collector so that the contact tip moves through the inepent part of the contact track. Sometimes the wizard is proposed to turn off the flow meter from the electronic control unit. But in this case, the fuel consumption increases noticeably. Thermalometric flow meters in car service conditions are unrepretentious. They are restored only in the conditions of repair production, such as Bosch.

We extend the resource

So that the air flow meter served longer, there are two means - to change the air filter in a timely manner and monitor the engine (in some old power systems, where the hose of the cutter gas suction system is "crashed" before the air flow meter). Prevent the premature failure of the flow meter can also repair the engine, as the wear of the piston rings and the valve seals leads to an increase in the content of oil in crankcase gases, and this, in turn, causes clogging of the parts of the flow meter with an oily flare.

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Air Flow Sensors Air Flow Sensors

The air flow sensor serves to measure the amount (volume or mass) of the air consumed by the air. The value of the mass of the incoming air, measured directly by the air flow sensor or calculated by the engine control unit by its volume, is one of the basic parameters in determining the duration of the opening. Air flow sensor is installed after the air filter before the throttle. From the side of the input part of the air flow sensor housing there is a mesh or laminating cells, leveling air flow throughout the air conditioner.

There are various designs of air flow sensors, but each of them can be attributed to one of two types - the sensors of the volume flow of air, and the mass flow sensors. Mass flow sensors (DMRV) are more preferable, since the mass flow rate is measured directly (DMRV takes into account the temperature and pressure of atmospheric air), due to which the engine control unit can more accurately calculate the required amount of fuel injected.
In addition, the design of the mass flow sensor (DMRV) does not have mobile mechanical parts. But due to the complex device of the mass flow sensors, in earlier engines control systems used mainly sensors of the volume flow of air. Sensors of the volume flow of air are less preferred, since only the volume of flowing air is measured. And the mass of air (like any other gases) fills, for example, the volume is equal to one liter, it depends very much on its pressure and temperature.

The motor control unit calculates the mass consumption of air, additionally, given the atmospheric pressure and readings of the air temperature sensor in the intake path. Each of these sensors has its error, as a result of which the calculated value of the mass flow of air may differ somewhat from the actual flow. The motor control unit calculates the mass of the mass of the air entered the mass of the fuel required for each cylinder. It should be noted that all air flow meters determine the continuous flow rate, and the fuel is injected with the injectors of portions, synchronously with the work of the cylinders.
The output signal of the air flow sensor may be analog or digital. In the first case, depending on the air flow, the voltage of the output signal of the sensor changes, in the second case, the frequency or diet of the output signal of the sensor changes. For example, the output signal of some GM production mass flow sensors, Mitsubishi is a rectangular voltage with a changing frequency. With an increase in the flow of the air flowing through the air sensor, the output frequency increases.

Air flow sensor

Most air volume flow sensors work according to one of the two principles: either the principle of the calculation of the vortices of the pocket (some sensors produced Mitsubishi, Chrisler ...), or the principle of displacement of the potentiometer slider using a blade placed in the stream of the air-consumable air. Air flow sensors operating on the principle of the calculation of vortices of pockets have high reliability, as they do not have mobile mechanical parts.

The air flow sensor operating on the principle of counting the pocket vortices.

Sensor of volumetric air flow, with a mechanical measuring potentiometer.

Potentiometric type potentiometric type of bosch type air flow sensor.
The volume flow sensors operating on the principle of displacement of the potentiometer slider using the measuring blade have low reliability, since their design includes movable mechanical elements. The blade of such a sensor is spring and placed in the stream of the air consumed by the air so that with increasing air flow, the blade is shifted proportional to the stream. The flow of the consumed air engine has a pulsating character, and to reduce the effect of pulsations of the measuring blade synchronously with the pulsations of the air flow, the sensor blade is connected to the damper. The potentiometer slider is mechanically connected with the measuring blade, which due to this is shifted by the value, proportional to the air flow. The measure of the volume of the air flowing through the air sensor is the output voltage of this measuring potentiometer. The measuring potentiometer of the air flow sensor is made on a ceramic substrate. Resistors of the voltage divisor are applied to the substrate, the conclusions of which are placed in a row and coated with contact resistive layer. The potentiometer slider is pressed to the contact resistive layer, due to which the voltage on the slider is equal to the voltage at the point of contact with the resistive layer.

Bosch Production Sensor Sensor Potentiometer.
With each change in the position of the blade, the slider moves along the contact resistive layer, gliding on it. Such movements of the slider gradually abrupt the contact resistive layer, which leads to the emergence of "scoring" of the measuring potentiometer. When the slider hit in the zone of dustiness, where the contact resistive layer is worn up to a ceramic substrate, the electrical contact between the slider and the resistive layer deteriorates, as a result of which the output voltage of the potentiometer no longer corresponds to the position of the movable flow meter blade - that is, the output voltage of the sensor does not correspond to the magnitude Consumable air engine. A typical malfunction of the sensors of the volume flow of air operating on the principle of displacement of the potentiometer slider is the mechanical wear of the resistive layer. Also often occurs to subdink the blade of the sensor. The reasons for the subflinking of the blade can be blades of the blade, deformation (curvature) of the blade due to severe cotton in the intake manifold or due to the contamination of the aircraft of the sensor. The method of diagnosing the sensor of the volume flow of air operating on the principle of displacement of the potentiometer slider is similar to the diagnosis method of the potentiometric sensor of the throttle position (or any other potentiometric position sensor).

Mass Air Flow Sensor Mass Air Flow Sensor (MAF SENSOR)

The measuring element of the mass flow sensor of the air is preheated to a certain predetermined temperature of a wire or film element. The flowing air flow cools this element, but the electrical circuit (usually embedded in the flow meter) controls its heating power and heats the measuring element to its former temperature. The larger air flow passes through the flow meter, the greater the heating power is required to maintain the specified temperature of the measuring element. Thus, the power of heating the measuring element of the flow meter is a measure of the magnitude of the air flow sensor. The magnitude of the heating current of the measuring element is converted to the output signal of the sensor - in most cases in analog voltage, in some types of flow meters into a rectangular voltage with a changing frequency.

Bosch HFM5 Mass Air Flow Sensor

There are several constructs of air consumption sensors, but in last years A large distribution was obtained by a mass flow sensor HFM 5 manufactured by Bosch.

Bosch HFM5 Mass Air Flow Sensor.
Bosch HFM5 mass flow sensor output signal is a direct current voltage varying in the range of 0 ... 5v. The output signal voltage of the sensor depends on the size and directions passing through the air flow sensor. With zero air flow (the engine is stopped, the ignition is turned on) the output voltage of the air flow sensor is 1,00V. When the engine works, air flows through the sensor, and the greater the air flow, the higher the value of the output voltage of the sensor. On certain modes of engine operation, short-term reverse air flows may occur - when the air moves in the direction from the engine intake manifold to the air filter. The Bosch HFM5 mass flow sensor is capable of registering reverse flow of air, while its output voltage decreases to the values \u200b\u200bof the smaller 1,00 V in proportion to the reverse flow value. If the signal from the mass flow sensor has deviations from the norm, the engine operation is significantly deteriorated - the fuel consumption increases, the "receiver" of the engine is reduced, the engine operation becomes unstable on the established modes, the engine becomes a cold start. The deviations of the output signal parameters can be associated with the "deterioration" of the characteristics of the air flow sensor, the sublict of the "unaccounted" air into the inlet path, the instability of the supply voltage of the sensor. In case of contact with the measuring element of the contamination sensor, the speed of the sensor reaction is reduced to changes in the air flow, as well as the measurement accuracy is reduced, which, as a result, leads to the preparation of the fuel-air mixture with incorrect composition. Intensive imposition of contaminants on a sensitive sensor element may occur due to late replacement of the air filter. Sometimes there is no damage to the sensor when the output signal is constantly within the limits of 1.00V and with an increase in the air flow, it does not change. The engine starts normally, but immediately stalls. In most cases, the engine control unit can only determine the fulfilled flow meter. The "deterioration" characteristics of the sensor are determined by the control unit in rare cases.

Bosch HFM5 Sensor Output Signal

To view the oscillogram of the voltage of the output signal of the Bosch HFM5 air flow sensor, it is recommended to use the differential oscillographic probe. The connector of the differential oscillographic probe must be connected to the differential analog input No. 6 USB AUTOSCOPE II. Black clamp type "crocodile" of a differential oscillographic probe should be connected to the "mass" of the engine of the diagnosed vehicle. The negative probe of the probe (black) must be connected in parallel "signal mass" of the sensor (terminal No. 3 of the sensor connector), the positive probe of the probe (red) must be connected parallel to the signal output of the sensor (terminal No. 5 of the sensor connector).

Connection diagram to the Bosch HFM5 bulk air flow sensor.

1. connection point of the black clamp type "crocodile" of a differential oscillographic probe;


2. negative probe connection pointdifferentialoscillographic probe (black);


3. point Connection Pointdifferentialoscillographic probe (red).

Measurement of the transition time when power is applied.

At the moment of inclusion of ignition, the supply voltages are supplied to the sensors and actuators of the engine control system, including the air flow sensor. Immediately after the power supply to the mass flow sensor, Bosch HFM5 is heated its sensing element to the operating temperature, while the sensor temperature stabilizes, the transition process occurs.

Oscillogram of output voltage of a serviceable mass flow sensor Bosch HFM5 when feeding supply voltages.
A: (engine stopped) and equal to 0.99 V;
AT.power on the sensor and equal to ~ 0.5 MS.
The time of the transition process of the output signal of a good sensor does not exceed the Milliseconds (MS) units. Pollution, deposited on a sensitive sensor element, warm up with it. If the number of deferred contaminants is significantly, the time of heating the sensitive element to the operating temperature increases, respectively, the duration of the transition process increases.

Oscillogram of output voltage of the faulty mass flow sensor Bosch HFM5 when feeding supply voltages.
A: Voltage value at the time of the specified marker. In this casecorresponds to the voltage of the output signal of the DMRV at zero air flow(engine stopped) and equal to 0.92V;
AT. The value of the time interval between two markers. In this casecorresponds to the time of the transition process of the output signal when filingpower on the sensor and equal to ~ 70ms.
The time of the transition process of the output signal of the sensor with a contaminated measuring element can reach tens, and sometimes hundreds of milliseconds.

Measurement of the output voltage at a zero air flow.

Measurement of the voltage value of the output signal of the sensor at zero air flow is carried out with the engine stopped and the ignition turned on. For the mass flow sensor, Bosch HFM5 air flow rate, the value of the output voltage is equal to 1V ± 0.02 V.

Measurement of output voltage with a sharp passage.

Measuring the maximum voltage value of the output signal of the sensor with a sharp passage is carried out by a sharp opening of the throttle for a short time (no more than one second), provided that the transmission mode switch is in the NEUTRAL position and the engine is warm to the operating temperature. Attention. The method of measuring the maximum value of the output signal of the air flow sensor with a sharp passage is applicable only if the accelerator pedal of the diagnosed motor is connected to the throttle valve mechanically (using the cable / levers) and only for atmospheric engines (the diagnosed motor is not equipped with a turbine / compressor) . At the moment of cutting penitz, the following occurs. When the engine is running on idle speed without load, filling the intake manifold air is strongly cut, since the air flow in the intake manifold is limited to the throttle and idling valve. The absolute pressure in the intake manifold is lower than atmospheric by 0.6 ... 0.7 Bar. The mass of the filling reserves is insignificant. With a sharp opening of the throttle, the air is dramatically rushes through the open throttle in the intake manifold and quickly fills the scope of the collector until the absolute pressure in it reaches the value close to the atmospheric. This process occurs very quickly, as a result of which air flow through the air flow sensor reaches the values \u200b\u200bof close to the maximum. After the absolute pressure in the intake manifold reaches close to the atmospheric, the value of the flow of the air flowing through the air sensor becomes the proportional frequency of rotation of the engine crankshaft.

Oscillogram of output voltage Output signal Bosch HFM5 with a sharp passage. The output voltage of the maintenance signal of the Bosch HFM5 mass flow sensor immediately after the sharp opening of the throttle should be briefly increasing to a value of at least 4.0V. In the case of a significant contamination of the sensor element of the sensor, the sensor reaction rate is reduced, and the waveform form of the output signal of the sensor becomes somewhat "smoothed". The contaminated sensor deposited on a sensitive element form a heat insulator that reduces the intensity of cooling the sensitive sensor element, which leads to a decrease in the heating current and the output signal of the sensor (respectively, the amount of fuel supplied to cylinders) is reduced.

Oscillogram of voltage output signal of a faulty mass flow sensor Bosch HFM5 with a sharp passage.
Due to the reduction in the reaction rate, the sensor ability to register rapid changes in the size and direction of air flow deteriorates. As a result, after a sharp opening of the throttle, the output voltage of such a sensor already "does not have time to achieve a value of 4.0V. Sensor faultsbosch HFM5 air consumption is eliminated Only by replacing it.

Air flow meter in a car, like all the components in it, are subject to defects. This electronic component in the machine is also called DMRV - a mass flow sensor. Unfortunately, despite modern technologies This sensor can quickly fail, delivering a mass. Today we suggest learn about the air flow meter in your car, as well as about the various signs of the malfunction of DMRV, about the reasons for its breakage and the cost of repair.

Why is this sensor called air flow meter or air flow sensor?

The fact is that this important sensor is set, as a rule, in the engine inlet system and is located between the housing and the throttle. And this sensor is equipped with both gasoline and diesel cars.

Using the air flow meter, the electronic motor control unit determines the mass of the absorbable. Based on data from the sensor, the electronics adjusts, which in the required quantity must be mixed with incoming oxygen. This allows you to create an optimal fuel mixture in the combustion chamber of the engine for perfect combustion.

Unfortunately, the air consumption sensor often becomes the reason for the emergence of errors in the electronics of the car, which is eventually reflected in the engine operation. For example, if the air flow meter is faulty in the machine, the engine engine stops working in optimal mode. As a result, in most cases, the motor begins to work in emergency mode, and warning appears on the dashboard.

The main minus of the air flow sensor is its cost. For example, a new air flow meter can cost 3000 rubles and even 30,000 rubles. Everything, of course, depends on your brand and model of the car and from what you want to buy a sensor - original / non-original.

But most often the cost of DMRV on average varies from 3750 - 12,000 rubles.

Unfortunately, since the air flow meter is an extremely sensitive component, then it can often quickly fail with incorrect installation. That is why we do not recommend independent replacement Sensor.

By the way, the replacement of the flow meter on average takes from 15 to 60 minutes.

And so how does the air flow sensor work, what are the most frequent signs of its malfunction and what to do in case of breakage?

Air flow meter function

Air flow meter (DMRV) is a relatively small component having great importance in proper work Engine control systems.

Almost all modern at present use air flow meter to calculate the optimal fuel injection into the combustion chamber. The flow meter is located in the intake manifold between the choke and the air filter.

In addition to the mass calculations, the sensor determines the temperature and pressure of the oxygen. Based on the values \u200b\u200bobtained, the engine control unit calculates the amount of fuel required to feed into the engine and the ignition time. In diesel cars, the air flow meter also affects the operation of the exhaust gas recycling system.

Until the 1980s, a mechanical sensor for determining air flows was used in cars. But today the mechanical sensor is no longer able to cope with modern demands Modern gasoline and diesel engines.

Modern types of DMRV

Conventional modern air flow meters in the car are equipped with two platinum resistors (heating metal threads). The first resistor is shielded from passing air, the second is directly in the air flow. DMPV is connected to a car electriable. With the help of electricity in the sensor, both resistors are heated.

But the temperature of two resistors is naturally different, since the unshielded resistor is constantly cooled by the undergoing air flow. The shielded resistor heats up faster and more. As a result, information about two different values \u200b\u200bcomes to the electronic engine control unit. Based on the difference of values, the engine control unit and determines the mass.

In order to prevent rapid pollution of DMRV provided forced system Cleaning. For example, after turning off the motor, the sensor is heated. Due to this, the sensor is cleared of contaminants.

Also enough recently appeared the new kind DMRV sensors. This new generation of air flow meters uses the heating film instead of wire. This is a thin film with a thin ceramic layer.

The new type of sensors is also connected to the car's power grid. Electricity keeps the sensor at a certain temperature of heating. When the air cools the sensor, then it has to be heated again at the expense of the current. Accordingly, the more air flow passes through the sensor, the more it cools.

Accordingly, the larger the time is necessary to restore the predetermined heating temperature of DMPV.

It is according to the desired heating volume an electronic engine control unit and determines how much air passes through the sensor and, accordingly, how much fuel is optimally submitted to the combustion chamber.

The advantage of this type of sensors is that they do not require a cleaning system with high temperature heating.

Signs of air flow meter fault (DMRV)

The air consumption sensor is not only important for the power of your car, but also necessary to regulate the minimum level of pollutants in the exhaust system of the machine. If the air flow meter is faulty or contaminated, it will not give the correct indications of the engine control unit. Outcome: The optimal amount of fuel will not be supplied to the combustion chamber.

As a result, it may turn out that the fuel injection system will be supplied to the combustion chamber or an inlet channel of the engine or too little or too much fuel.

Usually, when DMRV malfunction, the symptoms vary from the loss of power, the loss of smoothness of the stroke and the instability of the engine speed at idle, to drying in the ignition system and incorrect exhaust. Sometimes, due to breakage of the mass flow sensor, the air from the exhaust pipe can go black smoke.

However, we draw your attention that such signs may appear with other car malfunctions. For example, similar symptoms of breakage can be with a turbocharger malfunction or due to the malfunction of the ignition system. Therefore, these signs of malfunction cannot be 100% indicators of the failure of the air flow sensor.

Under certain circumstances, if the mass flow sensor starts to work incorrectly, the car engine usually goes into alarm mode (emergency program). At the same time, as a rule, on the dashboard of the car.

This program is needed to protect the motor from damage and save more or less clean exhaust as possible. Naturally, the engine capacity is reduced. For the owner of the car knew that the motor switched to the emergency program and invented the icon on the tidy " Check engine".

Also in the electronic system of the car in memory is recorded, with the help of which, when diagnosing, you can find out the reason for the inclusion of the emergency program of operation of the power unit.

Checking the air flow meter

Since the malfunction of the air flow sensor leads to an emergency mode of operation of the motor, as well as to the appearance of a malfunction error in the computer, the most reliable way to find out the reason for the icon on the engine check panel is the electronic car diagnostics. During this diagnosis through a special connector, a specialist connects equipment for reading the error machine.

However, it happens that there are no active errors in the car's memory. What to do in this case, if you still have signs of DMRV fault?

Naturally, in this case, a visual inspection of the air flow meter is necessary. True, in most cases, the visual inspection will not be able to accurately determine the fault of the sensor. In this case, it is usually a vehicle that offers owners to install a working DMRV worker for the test and check how the car will behave with a new sensor. Naturally, if after testing it turns out that the signs of malfunction went away, the old sensor unequivocally worked incorrectly.

True, this method is suitable only if the master is 99% confident that the cause of the engine is a malfunction of DMRV. The fact is that it is not always a car mechanic there is a worker DMRV in stocks for your car model.
In this case, you will have to buy a new sensor.


Naturally, if the malfunction has not been associated with the sensor, you just throw out extra money. And considerable, because DMRV is very expensive.

The most simple test for checking the performance of the air mass flow sensor is a simple test that anyone can do.
To do this, you need to de-energize the sensor.

If the engine after disconnecting the air flow meter began to work better, then, most likely, DMRV is faulty. However, this test, unfortunately, is not suitable for all cars.

Causes of defects in air flow meter

Air flow meter is a wear-resistant component in the machine. But nothing is forever in our world. Naturally, the more machine mileage, the more spare parts wear. This also applies to the mass flow sensor. For example, as the car's mileage increases each time, DMRV sends the engine control unit more and more incorrect values.

And sooner or later DMRV fails. Unfortunately, at first you can not notice the wrong operation of the motor. But as the sensor wear is increasing, you will begin to notice that the car behaves wrong. First, the first sign of malfunction DMRV is.

But not always the failure of the air flow sensor is associated with a large mileage of the machine. Sometimes air flow meter can fail very early.

For example, if you often drive quickly into heavy rain, then water can pass through the air flow sensor.

As a result, water can short term Cancel the sensor defect. In addition, the sensor can quickly fail due to the leakage of the intake system or due to late replacement of the air filter. The fact is that if sand and other dirt from the filter or from the street will fall on the sensor or from the street, it will not work well for a long time.

Cleaning air mass flow sensor

In some cases, the DMRV malfunction can help clean it. For example, if the reason for the improper measurement of the volume of incoming air into the engine is associated with the contamination of the air flow meter. However, when cleaning the DMRV, caution should be exercised, since the sensor sensor parts are very sensitive to the touch.

To clear the mass flow sensor, special car cleaners apply. True for cleaning the sensor will have to remove from the machine. After cleaning and drying the sensor, it is set back to the car. In this case, also check. If it is contaminated, you need to install a new filter.

Repair and expenses

If a mass flow sensor has failed in your car, we recommend producing. Fortunately, the cost of the sensor replacement is small, since in most DMRV machines are easily accessible. In most cases, it is necessary to replace air flow meter from about 15 minutes to 1 hour depending on the brand and car model.

Unfortunately, in many modern cars for the replacement of DMRV, a special tool is required. Also in many modern cars after replacing the air flow sensor, it may be necessary to "prescribe" the flow meter in the engine control unit, thereby informing the electronics about the new sensor. Unfortunately, therefore, not all car owners familiar with the car repair can independently change the DMRV in their car.

Is it worth buying a non-original air flow sensor? Unfortunately, the cost of DMRV is not small. Therefore, many drivers are often interested in the question, is it possible to purchase it analogue instead of the original flow meter?

Unambiguously to answer this question. It all depends on the brand and model of your car and of course from the manufacturer of sensors. For example, there are cars on the market for which non-original sensors you will not find.

If you still decided to purchase a non-original DMRV, then choose only reliable suppliers among well-known manufacturers.

Unfortunately, the cost of mass flow sensors is rather big (especially in modern new cars). So we advise not to save, because, spending a rather big money to the neoriginal, you may encounter a small service life of the sensor, and ultimately soon or later get the original flow meter.

Agree, it is unreasonable.

Remember that sometimes savings can get out sideways. Especially when it comes to electronic automotive components.

We also want to note that in some cars the mass flow sensor is built into the engine control unit. In this case, the cost of repairing the sensor can do in a very large amount.

In this case, you have the only way to save, it look for a company that is engaged in the repair of such aggregates. Typically, such companies repair similar blocks, changing the mass flow sensor built into the engine control unit.

Yes, the repair in this case will not be cheap, but nevertheless incompandulating with the cost of a new engine control unit.

When the internal combustion engines are working with which modern cars are equipped, the fuel and air mixture is combustion, for the formation of which, as it is not difficult to guess from its very name, it is necessary to mix fuel with air, and in strictly defined proportions. Accordingly, systems that are responsible for the formation of this substance, at each moment of the functioning of the power unit must accurately "know" the consumption of each of its components. The value of this indicator for one of them helps to determine the mass flow sensor (DMRV). It should be noted that it is present in the design of only injection engines, and if the drivers notice the signs of DMRV malfunction, then it should be checked and, if necessary, replace it.

What does the air flow sensor look like by car

This important sensor is located directly behind the engine air filter, and even more precisely, then just between it and the throttle node. It is arranged so subtle, which allows with high accuracy to measure consumption of only the air, which is well cleaned from mechanical impurities

During the operation of the DMRV transmits the electronic signal control system, the signals that are processed and interpreted as the volume of air that is supplied to form the fuel and air mixture. For the normal operation of the power unit, the volumetric ratio of liquid fuel (gasoline, diesel fuel) and air should be close to 1x14. If this proportion is broken, then there is a significant loss of the power of the motor, or the fuel reservoir (this is by the way, the main signs of the DMRV fault). Information obtained from the sensor that determines the mass flow of air helps to be avoided.

The DMRV grows a measurement of the amount of air, which per unit of time enters the fuel ramp. It transmits this data to the ECU, which instantly makes the calculation of the amount of liquid fuel, which must be submitted to form a mixture, and gives the corresponding "orders" responsible for this engine devices. Thus, if, for example, press the accelerator pedal, then the air begins to immediately act more, the DMRV instantly determines, sends data to the ECU, which in the appropriate proportion increases the supply of gasoline or diesel. If the amount of air decreases, the volume of liquid fuel supply is reduced.

From the point of view of the design, there are also three types of such sensors are actively used:

• Based on the Pito tube;
• With thermometric meters;
• With film meters.

DMRV, built on the basis of PITO tube, are considered to be outdated and in the newest models of engines are not used. They are so-called blade flowmeters, the main elements of which are associated with potentiometers and gently fixed on the axes of the plate. By changing its position under the influence of air flow, they affect the potentiometer, which changes its electrical resistance.

Mass flow sensors with thermoenemometric type meters are quite expensive, although very effective. They have special heat exchangers consisting of two platinum threads that are heated undergoing electric shock. One of them is blown by the air flow, the second remains the control, and the difference in current passing through them, the ECU calculates the amount of air incoming to form a fuel mixture. DMRV with film meters are considered the most modern. According to its principle of operation, they are almost similar to thermoelectrician, only platinum filaments are used in them, and ceramic elements with platinum spraying.

The main signs of a mass flow sensor fault

The malfunction of DMRV, as already noted above, leads either to re-enrollment, or to depletion of the fuel mixture with gasoline or diesel fuel, which negatively affects the operation of the engine and can lead to its serious breakage. Most often, DMRV faults are associated with air filter tornness: the air is cleared well, and the mechanical particles contained in it fall into the sensor, which is the cause of its breakage. It should be noted that the mass flow sensors are unrestracted devices, and if they fail, they have to change them.

Practice shows that the main signs of DMRV fault are as follows:

• Check Engine error appears, which indicates that the signal level of this sensor is very low;
• The engine consumes more fuel than usual;
• The power unit is badly started, its power is reduced, it begins to stroke;
• The car is badly accelerated;
• The engine works or on elevated, or on low revs.

Of course, all signs can manifest themselves with other car malfunctions, but in any case, if at least one of them is detected, it is a good reason to visit the station maintenance. However, check, DMRV for malfunctions, it is possible and independently, without referring to the specialists of a hundred.

With the arrival of the engine of the internal combustion of electronic processor devices and injector systems of formation of the fuel and air mixture, it was necessary to use special sensors defining the parameters of the mass flow in the intake manifold. The first was the air flow sensor.

What is DMRV in the car

The controller controlling the amount of fuel injected into the inlet should receive information about the mass flow moving through the intake manifold. For this purpose, DMRV readings are used - a device for fixing the mass flow of air. The more accurate information, the better the mixture.

The reason to get acquainted with the "piece" DMRV and its location in the engine appears at the first symptoms of the fault sensor of the mass flow of air. Causes can be:

• unstable engine operation, both idol, and when driving on the highway;
• motor starts with great difficulty, especially if before it worked under load;
• the appearance on the dashboard of the indication indicating the problems with the engine and the fuel consumption has increased markedly.

Device and operation of air flow sensor (DMRV)

Considering the fact that AvtoVAZ generously spacked the mass flow sensors to all more or less workers, from tens to the fourteenth model, it is worth knowing how it works and works this miracle.

The principle of operation of the DMRV uses a change in the temperature of the metal layer of 0.07 mm, which is welded on the ceramic layer of the sensor, or thin platinum wire under the action of air flow. The air flow sensor is established on a special power supply, and is transferred to the central part of the cross section of the air collector before the throttle to reduce the influence of local twists.

In addition to the platinum layer, two thermistors are pasted on the surface of the silicon element for fixing air temperature and sensitive element. A small electroscheme manages the measurement process, and under certain conditions it starts the self-cleaning mode of the sensor from the lacquer and oil films of the dirt. At the same time, on the surface of platinum, the temperature flies up to 1000 o C, and air oxygen organic substances Transfer to combustion products.

Important! A special danger to the flow sensor represents mineral dust from the refractory oxides of metals. Often, in the cleaning mode, they "tightly" are accumulated to the platinum film, thereby create a thermal insulating layer, distorting data on air flow data. Remove such a flare with simple solvents - unrealistic.

We check and evaluate the symptoms of malfunction DMRV

It is clear that signs of malfunction are the conditional thing, problems may not be limited to the efficiency of the mass flow measurement device, so before deciding on further procedures it is worth a couple of additional tests for DMRV diagnostics.

To do this, you can perform:

• check-in with a disconnected mass flow sensor;
• measuring the testimony of the potential of the DMRV;
• old military trick - temporarily replace the problem sensor on a well-good air consumption sensor, taken for rent at the gullible neighbor.

Tip! You can still check the state of the mass flow measurement sensor with a visual inspection, but for this you will need experience with similar sensors, which is most accessible to experienced masters. Flip dust is not good, it does not always mean the sentence.

If you are not a happy owner of the controller ECU Y7.2.m7.9.7., Just disconnect the connector block on the air flow sensor. With a different type of ebeushki, the malfunction test will not work. What will happen if you turn off the mass flow sensor DMRV? The engine will start and work. In this case, the logic of the controller, which determined the full fault of the air flow sensor due to the removed contact, will translate it into an emergency mode according to air flow information and will use its averaged values \u200b\u200band information about the position of the throttle.

In practice, this will mean an increase in idle speed up to 1400 rpm, depending on the murdration of the valve position sensor. The most important thing, in sensations in the test acceleration, you will feel that the cutting and the pickup of the machine increased markedly. Conclusion: Most likely the DMRV is bad, but the question is how much? The main idea of \u200b\u200bchecking is intended to not rush to buy and change the cheapest air flow sensor, and try to find a compromise. It is possible that the sink or other manipulations of the DMRV can be restored.

Measurement of the potential for DMRV

If on your car there is a Boschvsky version of the flow sensor with catalog designations 0280218004, -037, -116, it is easier and more reliably measured directly by the potential issued by a mass flow sensor of DMRV. We measure with any instrument that allows you to operate with a range of 0-2 and the accuracy of a hundred volt. Try to measure the use of a proven device, without additional extension cords, wires and needles.

Find the DMRV sensor housing in the air collector is quite simple. In the firm connector, tightly closed with a rubber cap, fits the harness of the wires of different colors. The DMRV pinout distinguishes the following:

• The 1st wire provides the sensor input signal, usually a yellow wire;
• The 2nd and 3rd wires are responsible for the power supply, "+" and "-", respectively;
• The 4th wire is connected to the main relay.

To measure the potential, use the first and third harness wire. The options for connecting the probe of the measuring device are several, but it is not necessary to use paper clips or thin sharp wires. They can significantly affect the accuracy of measurement. It is possible to finely sharpen copper tips of probe and pierce the insulation of the wires, as close as possible to the contacts.

Measurement is performed when the ignition lock is on, but shoved the engine. If the connection is performed correctly, the device will show the value from 0.996 - for a new sensor, up to 1.05 - for almost the "dead" and requiring replacement.

Estimation of the state of DMRV by external inspection

To remove the sensor, it is necessary to unscrew its mounting on the air duct, relax the clamp and disconnect the corrugated piece of the pipe. The sensor itself is fastened with a pair of screws that can be renewed with a top ten, removing the chip with wires, you can carefully remove the housing from the socket. After looking at the surface, you can see the traces of dust and oil. The presence of stains and dirt suggests that self-cleaning mode does not help him. But you need to find the cause of pollution.

Pay attention to the rubber ring sealing the connector. It performs the functions of blocking a possible supply from the boost space into the cavity of the sensor of the dirty and the air evaporation. With the normal position of the rings of the suction, most likely, was not.

Most often, the dirt on the surface of the sensor is settled due to the poor condition of the air filter. Sometimes, on the recommendation of numerous specialists, car enthusiasts process the filter cartridge with a special oil aerosol. Typically, such a drug is used on full-scale zero resistance air filters. But the effect is achieved for a new filter for the same 5-10 thousand km. Special protection for a mass flow sensor of air from dust microparticles Aerosol will not create.

On the video - a little more about the sensor of the mass flow of fuel: