Home > Industry Information > Definition And Application Analysis Of Intake Manifold Absolute Pressure Sensor
The intake manifold absolute pressure sensor is a core component of the D-type fuel injection system of automotive engines, and is simply referred to as the MAP sensor.
It is mainly used to detect the vacuum degree changes in the intake manifold. This sensor converts the pressure signal into a voltage signal and transmits it to the Engine control unit (ECU),
which serves as the main basis for controlling the fuel injection volume, ignition timing and air volume calculation.
Pressure sensor: Responsible for measuring the absolute pressure in the intake manifold. It is usually achieved by using miniature silicon pressure sensors or piezoelectric sensors.
Signal conditioning circuit: It is used to process the raw signal obtained from the pressure sensor and convert it into a digital signal for processing by the engine control unit.
Connection lines: Transmit signals and power connections between the sensor and the engine control unit.
The common types of intake manifold absolute pressure sensors include piezoresistive type, capacitive diaphragm type and surface elastic wave type,
among which piezoresistive type and capacitive type are the most widely used types.
· Piezoresistive type: Composed of a silicon wafer, an absolute vacuum chamber and an IC amplification circuit, it detects pressure changes by the deformation of the silicon wafer
· Capacitive type: It uses an elastic diaphragm and the housing to form a variable capacitor, and outputs signals through the capacitive effect;
· Variable inductance type: By expanding the membrane box to drive the core to move, the inductance value of the induction coil is changed;
· Surface elastic wave type: The pressure signal is output by detecting the change in the delay time of surface wave propagation through the transducer on the piezoelectric substrate.
The intake manifold absolute pressure sensor is based on absolute pressure measurement. It takes the internal sealed vacuum chamber as the reference and adjusts the output signal
by causing changes in the sensor resistance value due to pressure variations.
· Pressure sensor measurement: The absolute pressure sensor of the intake manifold is located inside the intake manifold or directly connected to it. When the engine is running,
the airflow pressure in the intake manifold will be applied to the sensing element of the sensor.
The degree of deformation of this component is proportional to the pressure. Therefore, the magnitude of the pressure can be determined by measuring the degree of deformation.
· Signal processing and output: The sensor sends the measured pressure signal to the signal conditioning circuit for processing. The signal conditioning circuit is responsible for amplifying,
filtering and linearizing the pressure signal, and converting it into a digital signal.
These digital signals are usually transmitted to the engine control system in the form of standard voltage or current for processing and analysis.
Fuel adjustment: By measuring the absolute pressure in the intake manifold, the sensor can provide accurate pressure data to the ECU. The ECU adjusts the fuel injection volume based on these data
to ensure that the engine achieves the best combustion efficiency under different operating conditions.
Ignition timing control: Changes in pressure in the intake manifold can also affect the ignition timing. The pressure data provided by the sensor enables the ECU to adjust the ignition timing according
to different working conditions to offer the best power output and combustion efficiency. Fault diagnosis: The intake manifold absolute pressure sensor can also help detect faults in the engine system.
By monitoring the pressure data output by the sensor and comparing it with other sensors and parameters, the ECU can detect faults in the sensor itself or other related components, and trigger fault codes for technicians to diagnose and repair.
Diesel is one of the most common forms of fuel for vehicles, especially large transportation, construction and agricultural vehicles. Pressure sensors are crucial for keeping diesel engines as clean as possible.
The particulate filter inside the engine is used to capture soot and other particles present in the exhaust gas before it can be discharged into the atmosphere. Then the filter needs to be cleaned by burning off the particles.
This can be achieved either by using an active system that heats the filter to the combustion temperature of the soot or by using a passive system with a catalyst.
The engine control system calculates and controls the fuel injection volume based on the pressure signal provided by the intake pressure sensor, combined with data from other sensors (such as throttle position, engine speed, etc.),
to ensure that the engine can achieve the optimal fuel-air mixture ratio under various operating conditions.
In turbocharged engines, the intake manifold pressure sensor is also used to monitor the pressure of the turbocharging system, ensuring that the turbocharger operates within a safe range and assisting
the engine control system in adjusting the boost pressure to achieve greater power output.
If the absolute pressure sensor of the intake manifold is damaged, the engine control system will be unable to correctly correct the fuel injection volume and ignition timing Angle, resulting in difficulty or failure to start the vehicle.
Furthermore, a malfunction of the intake pressure sensor can affect the detection of intake volume, causing unstable vehicle speed and a feeling of weakness when accelerating. In addition, the intake pressure sensor is also related
to the fuel injection system. A malfunction may result in insufficient or excessive fuel injection, further affecting the vehicle's performance.
1. Internal fault of the sensor
2. There is dirt at the sensor detection part
3. Poor contact, open circuit or short circuit in the sensor circuit
4. Fault of the engine control unit
Test voltage: Set the multimeter to the DC voltage range (10 or 20V), and measure the output voltage value of the intake sensor. It is approximately 0.9V at idle speed. As the speed increases, the vacuum decreases and the voltage rises.
If the signal voltage is lower than the normal value (possibly caused by a short circuit between the signal and ground, low reference voltage, etc.), phenomena such as insufficient power, difficult starting, high fuel level,
and the fault light being on will occur.If the signal voltage is higher than the normal value (which may be caused by an open ground wire, a short circuit between the signal and the reference voltage, etc.),
phenomena such as insufficient power, exhaust tailpipe sparks, and the fault light being on will occur. After eliminating the circuit fault and confirming that the reference voltage provided by the engine control system is correct,
if the voltage display still has problems, the sensor should be replaced.
Detection frequency: It should be measured with an oscilloscope. If the aforementioned method is used, it will be found that the measured voltage value does not change (approximately 2.4V). This is because it outputs a square wave.
When the engine speed changes, the vacuum degree of the intake manifold also changes. The amplitude of the output square wave remains unchanged (still 5V), but the frequency of the square wave changes.
If the frequency does not change or there is no square wave (at this point, it should be determined that the Map sensor is frequency-type), and if it is not a fault of the circuit (including the connection plug), then the sensor needs to be replaced.
The intake manifold absolute pressure sensor (MAP), as a key component in the fuel injection system of automotive engines, provides important data support for the engine control unit (ECU) by measuring the pressure changes within the intake manifold.
These data not only directly affect the adjustment of fuel injection volume and ignition timing, but also play a crucial role in the vehicle's power performance, fuel economy and exhaust emission control.
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