What are the advantages and disadvantages of automotive air flow meters?

1. Vane air flow meter: advantages: simple principle. Disadvantages: Obstruction of air intake. The signal changes slowly.

2. Measuring core: advantages: none. Disadvantages: There is air intake resistance, the signal is not accurate.

The above two have been eliminated.

3. Carmen eddy current type: advantages: it can directly generate digital signals.

Received by the computer. The signal is precise. Disadvantages: complex structure, high manufacturing cost.

4. ** type: advantages: low cost, accurate signal. Fast response. Disadvantages: Only analog signals can be generated.

If the computer receives it, it will also convert the signal.

An air flow meter is a device that measures the amount of air intake into an engine and is used in L-type injection systems.

The air flow meter is installed between the air filter and the throttle body, and some are mounted on the air filter, and some are integrated with the throttle body and installed on the engine.

The air flow signal is one of the main bases used to determine the basic fuel injection volume. According to its structural form, it can be divided into the following four types:

Fin-type air flow meter, which is a volumetric flow type. It was more popular in the 70s of the 20th century.

The Carmen vortex air flow meter, which is a volumetric flow type, is mostly seen in Mitsubishi and Toyota vehicles.

** type air flow meter, for the mass flow type, developed in the early 80s of the 20th century, now widely used.

Thermal film air flow meter, for the mass flow type, developed by General Motors of the United States, is mostly used in the cars produced by General Motors and Isuzu Corporation of Japan, and the electronically controlled fuel injection engines produced in China are also widely used.

1. Detection of fin air flow meterThere are two kinds of fin air flow meter: 5 lines and 7 wires, the 5-wire fin air flow meter does not have an oil pump switch, and the 7-wire fin air flow meter is equipped with an oil pump switch. The name and function of each terminal.

2. Detection of hot film air flow meterThe hot film air flow meter has low manufacturing cost, long life and is widely used. Santana era Superman, SGM Buick and other cars all use this air flow meter.

Fault symptoms of a broken car air flow meter:

The vehicle has idling and shaking, high fuel consumption, high-speed weakness, and black smoke from the exhaust pipe.

Check and analyze:

After the fault diagnosis instrument detection, the engine air flow meter data block is seriously exceeded, and the reason for the damage of the air flow meter is often the use of inferior air filter or the air filter is not regularly replaced, resulting in dust staying on the air flow meter hot wire for too long, resulting in its resistance value change is inaccurate or invalid, and dust will cause the throttle body to be too dirty.

The automobile air flow meter can pass through two parts: power supply voltage test and signal voltage test, in which the signal voltage test is the main basis for determining whether the air flow meter fails.

The function of the automobile air flow meter is to monitor the air intake of the engine, and convert the air intake information into an electrical signal and transmit it to the electronic control unit (ECU), which determines the fuel injection volume of the engine through this signal. The symptoms of failure or damage of automobile air flow meter include unstable idling, poor acceleration, increased fuel consumption, high-speed weakness, black smoke from the exhaust pipe, and excessive exhaust emissions.

Although the malfunction of the air flow sensor does not cause the engine to fail, it will affect the power performance of the engine. The damage of the air flow meter is often due to the air filter not being replaced for a long time or using an inferior air filter, resulting in the air flow meter hot wire dust accumulation time for too long, resulting in inaccurate or invalid resistance value changes, and dust will also cause the throttle to be too dirty.

It can be judged by measuring the output voltage data when the engine is running: The dynamic signal voltage at the signal end of the plug signalIn the case of engine idling, the standard voltage is; When accelerating to full load, the voltage signal can approach 4V. If it is not in this range, the air flow sensor itself is damaged, or it may be caused by dirt, and it can be cleaned.

It can be judged by measuring the output voltage of the sensor: Detect with a universal meterThe general voltage value is 5V, use a hair dryer to blow air into the sensor, if the voltage changes with the size of the incoming air volume, it is normal; If it does not change or changes little, it indicates that the flow meter is faulty, which needs to be replaced.

The role of the automobile air flow meter.

The air flow meter is one of the important sensors of the EFI engine, which converts the intake air flow into an electrical signal and sends it to the electronic control unit (ECU), which is one of the basic signals to determine the fuel injection, and is a sensor that determines the air flow of the suction engine.

In order to obtain the best concentration of mixtures in a wide range of operating conditions, electronically controlled gasoline injection engines must accurately measure the amount of air drawn into the engine at each moment as the main basis for ECU calculation (control) of the amount of fuel injected.

If the air flow sensor or line fails, the ECU cannot get the correct air intake signal, and the fuel injection volume cannot be controlled normally, which will cause the mixture to be too thick or too thin, so that the engine will not run normally.

The way to judge the good or bad of the air flow meter is as follows:

If the air flow meter is broken, the car will have idle shaking, weak acceleration, increased fuel consumption, and black smoke from the exhaust pipe, which will affect the performance of the car engine.

To judge whether the air flow meter is damaged, you can unplug the air flow meter, if the car can start normally, the air flow meter is damaged. The common reason for the failure of the air flow meter is the short circuit of the line, the open circuit or the abnormal air intake signal, which will lead to abnormal fuel injection, resulting in too thick or too thin mixture, resulting in poor engine operation or power loss.

How the air flow meter works:

During the use of an air flow meter, the gas flow is passed through the flow meter to propel the turbine blades to rotate. The number of revolutions of the impeller is directly proportional to the volume of gas passing through the air flow meter. A specially designed patented deflector is installed at the inlet of the flow meter to accelerate the flow of air into the flow meter as the flow rate increases.

The deflector frame is designed to eliminate any potential fluid disturbances such as eddy or asymmetrical flow. The push force on the turbine blades is also increased at the same time. This ensures that the flow meter is metered with high accuracy within the allowable error range, even in the case of small flow rates.

The air flow acting on the turbine blades is axial, and the turbine is mounted on the main drive shaft, which is equipped with high-strength ball bearings. After the gas passes through the turbine blades, the rotation of the turbine blades is decelerated by the gear set. The pressure in the inlet channel of the air flow meter is restored, and the channel design ensures optimal flow regime.

There are two types: one is called the Direct Measurement L-type, which is referred to as the Air Flow Meter. The second type is called the indirect measurement type D, which is referred to as the intake manifold absolute pressure sensor.

Damaged or affected air flow meters: Air flow meters in high-quality vehicles fail when there is no sign of an air flow meter, which mainly affects the energy performance of the engine. The possible phenomenon is as follows: idling.

Instability; increased fuel consumption; Acceleration.

Low; The exhaust pollution is serious, and it is impossible to enter the vehicle under normal circumstances, because when the air flow meter is abnormal, it is often accompanied by an incorrect indication of the amount of fuel injection, which directly leads to the inconsistency between the amount of fuel injected and the actual working state of the engine.

Over time, it will lead to accumulation in the engine cylinders. ECU cars need to test this method. The inlet air flow and air temperature are observed to remain constant, indicating that the air flow meter is damaged.

Replace the air flow and test instruments. The car stopped smoking, and the energy returned. The fault was resolved.

Based on this signal, it is possible to determine the amount of fuel injected. There is also a weak acceleration: the deviation of the output signal from the air flow sensor does not accurately reflect the actual air intake, resulting in a reduction in the amount of fuel injected controlled by the ECU, so the engine speed does not rise, summary:

The problem with air flow meters is:

Due to the lower air filter.

The USO or air filter is not replaced regularly, and the dust stays in the hot FIO of the air flow meter for a long time, resulting in an inaccurate or invalid resistance value. In addition, dust can make the throttle body dirty, and the car's air flow meter can also be damaged. There will be some repercussions:

Unstable idling, increased fuel consumption, damaged engine air gauge, low acceleration of TEM vehicles, black smoke (i.e., poor combustion, wrong air-fuel ratio), inability to run to maximum speed, no idling, etc.

A specially designed patented deflector is installed at the input of the flow meter to accelerate the airflow into the flow meter, thereby increasing the flow rate. A malfunctioning air flow meter will affect the energy performance of the engine. For example, the obvious symptom after the failure of the idle air flow meter is that the engine fault light will be lit, which will also lead to a decrease in engine power, difficulty starting the engine, uncertain operation signals, increased fuel consumption, unstable idle speed, low acceleration, backfire of the intake pipe, unstable exhaust and low acceleration "temperament" of the intake pipe, and black exhaust smoke will also lead to excessive exhaust slippery emissions.

Hot wire air flow meters are analog output voltage signal sensors, and most hot wire air flow meters increase the output voltage when the air flow rate increases. The internal temperature compensation circuit of the hot wire air flow meter is complex, and the output voltage analog signal is sent to the control computer, and the control computer calculates the engine load according to this signal, determines the fuel supply and ignition timing, and so on. *The waveform results can be compared and analyzed with reference to the maintenance data, usually the output voltage range of the hot wire air flow meter is from more than 4V when the throttle is fully open, and the output voltage should be slightly lower than the voltage at idle when the full deceleration is full.

It is normal for the amplitude of the waveform to appear to fluctuate constantly while the engine is running, so the hot wire air flow meter has no moving parts and therefore no inertia, so it can react quickly to changes in air flow. The clutter seen in the waveform during acceleration is actually the pulsation of the air flow on the air intakes of each cylinder under a low intake vacuum, and the super processing circuit in the control computer will clear these signals when they are read in, so these pulses have no effect. Highlights:

The output voltage of different models will be very different, whether it is at idle speed is also a way to judge the quality of the air flow meter, in addition to whether the fuel mixture is normal or smoke can also judge the quality of the air flow meter, sometimes it is very difficult to judge the quality of the air flow meter. Many bad air flow meters have too high input voltage at idle and can't reach 4V when the throttle is fully open. *Experimental method: Turn off all ancillary electrical equipment, start the engine, and let it idle to run, and after the idle speed is stable, check the idle output signal voltage (waveform in the figure).

Acceleration and deceleration experiments should have similar waveforms. Increase the engine speed from idle to full open throttle (the throttle opens at a slow medium speed during acceleration) for about 2 seconds, but not overspeeding; Then slow down back to idling for about 2 seconds; Accelerate sharply from idle until the throttle is fully open, and then back to idle; Lock the waveform and take a closer look at the air flow meter waveform.

Hello, car air flow meter It mainly detects the air intake of our engine. Based on the air intake of the engine, we can determine the basic injection volume of our fuel, which I hope will help you.

The air flow meter, also known as the air flow sensor, converts the intake air flow into an electrical signal and sends it to the electronic control unit (ECU) as one of the basic signals to determine fuel injection. In order to obtain the best concentration of mixture in an electronically controlled gasoline injection engine under various operating conditions, the amount of air drawn into the engine at each moment must be accurately measured as the main basis for ECU calculation of the amount of fuel injected.