Flow meter – what is it and what is it for in the car?
This element plays a very important role in coordinating the proper operation of the engine. How is it built and what does its operation actually mean?
What is a flow meter?
The flowmeter is a very simple device, whose task is to measure the flow of air through it. It is therefore an extremely important element, because it directly examines whether the composition of the air-fuel unit is as close as possible stoichiometric. Under this concept should be understood such proportions, when for every kilogram of fuel there is exactly as much air as needed to completely burn the fuel (for gasoline it is 14.7 kg of air for every kilogram of fuel).
The air flowmeter transmits the information obtained to the engine control unit, while this one can properly correct the condition of the mixture so that the optimal values are maintained. This is an extremely important function in the face of the proper functioning of the drive unit. It affects, among others on engine speed or complete combustion while driving.
General principle of the flow meter
Formerly, the functioning of the element was based on a flap with a lever assembly and an injection pressure regulator in the air duct. However, this solution was not very effective and often failed. The development of technology and electronics, as you can guess, favors new designs. And it is thanks to this that the flowmeter becomes only a measuring element over time, which transmits the information received by means of electrical impulses.
Currently, the sucked air flows smoothly around the thin wire found in the device. During operation, it heats up to about 100 ° C, which is a starting point for reading data later. The air flow causes the wire temperature to drop in proportion to its quantity. The purpose of the mechanism is to maintain a relatively constant wire temperature. If, therefore, its temperature drops quite significantly, this indicates an excessive amount of flowing air. In this situation, the controller must provide it with more electricity.
What’s more, as the air flow increases, more fuel can be delivered to the engine. It is also worth knowing that in resistors with a resistor, the temperature difference between the air going into the engine and the resistor is constant at about 180 ° C
Types of flowmeters
Older engine models usually have a flap, also called a volumetric flow meter. Its construction is built, among others from potentiometer, movable damper, air temperature sensor, return spring, silencer, non-return valve and regulator.
The essence of its functioning is the lifting of the movable damper, which was connected to the potentiometer. It comes to this as a result of a stream of flowing air. The second flap squeezes the air in the damping chamber, acting like an ordinary silencer. What is important, it eliminates sudden movements and protects against vibration of the measuring flap. Depending on the size of the flow rate, the angle of its deviation changes.
This information is transferred to the potentiometer’s slider, and the measurement module scales the obtained values. The indications obtained are proportional to the deflection of the flap, i.e. to the volume of the air flow. You need to know that the value of the sucked air is inversely proportional to the voltage obtained on the potentiometer. Then the signal is sent to the control unit.
The non-return valve reacts to the increase in the negative pressure in the structure. Its function is based on the protection of the damper in case of ignition of the fuel-air mixture in the intake manifold.
The second type of flowmeter is a mass flowmeter. It is located in the intake manifold just after the air filter. In this case, the said principle applies with the measurement of the current necessary to maintain a constant wire temperature. When the signal is sent to the controller with an increased current, it also indicates an increased air flow. The mass flowmeter has an additional thermistor, which is responsible for determining the temperature of the air sucked in.
How to avoid flow meter failures?
Widely understood prophylaxis is a very important factor. The key in this case is the systematic replacement of the air filter, if possible, with the original replacements. It’s worth taking care of the cleanliness and patency of the entire system. Try to avoid sports versions of air filters, because they transmit more air in a natural way, which increases the chance of various defects.
Another reason for the emergence of a failure is problems with gas installations. The flowmeters are very sensitive to so-called intake manifold arrows. Serious damage can occur even after one such event. Therefore, you should provide systematic reviews of your installation that will reduce the likelihood of problems with the flow meter.
It is often forgotten that the flowmeter fault may be caused by dynamic water driving. Although this mainly applies to off-road vehicles, the problem often occurs in passenger cars. Too quickly hitting the puddle can, for example, lead to the flow meter getting into the flow meter. water fog, which in turn leads to the firing of the wire.