Types of Sensors Used in Multi-Point Fuel Injection System

Multi-point fuel injection system infuses fuel in to the intake valves of each cylinder. Sensors located in the vehicle's fuel engine system helps the control unit to determine when certain functions need to occur. Typical sensors used in multi-point fuel injection system are as follows:

• Manifold Absolute Pressure (MAP) sensor: This sensor is located in the intake manifold and is used to measure its pressure.
• The measured information is sent to the Engine control unit (ECU) of the engine load which is essential to evaluate the amount of fuel to be injected.
• To monitor the air mass the ECU also needs to know the engine speed and air temperature.
• Throttle position sensor: It is a potentiometer which acts as an arm and moves along a copper trail thus varying the input voltage.
• This sensor is seated over the throttle body and converts the throttle valve movement in to voltage signal.
• As the throttle closes/ opens the voltage decreases/ increases accordingly.
• Intake air temperature sensor: It measures the temperature of the air entering the engine.
• Cold air being denser requires more fuel compared to warm air.
• Automated systems (computer) compensate for changes in outside air temperature by the means of air temperature sensor and thus maintains a perfect fuel-air ratio.
• Engine coolant temperature sensor: This sensor monitors the engine's operating temperature and allows it to be exposed to engine coolant.
• If the engine is cold enough, the sensor provides a high current flow by which the computer enriches the fuel-air mixture for cold operation.
• If the engine is warm, the sensor supplies information to the computer such that it makes the fuel mixture leaner.
• Oxygen sensor: It is also known as exhaust gas sensor.
• This sensor measures the oxygen levels in the engine as a means for checking the efficiency of combustion.
• An increase in the oxygen levels make the sensor's output voltage to reduce and a decreased oxygen level causes increased output of sensor voltage.
• When the computer receives data from the sensor, it alters the closing or opening of injector to maintain the right fuel-air ratio in order to achieve maximum efficiency.
• Vehicle speed sensor: It is located on the speedometer or the transmission gearbox.
• Vehicle speed sensor generates the signal in proportion to the vehicles speed. After receiving the signal, the speedometer uses it for indicator operation and converts to ON/OFF signal by amplifying the signal.
• ECU receives the signal and uses it as one of the signals for controlling various devices.
• Camshaft position sensor: This sensor informs the power-train control module (PCM) its position in respect to the crank shaft sensor.
• The position of the camshaft makes the PCM to know the timing of closing and opening of the intake valves.
• Also, the fuel injector and ignition timings rely on this position information.
• This sensor also allows the PCM in determining the cylinder which is on its compression stroke.
• Crank shaft position sensor: This sensor is also known as distribution rpm sensor that is used for cylinder identification and to detect engine speed.
• The sensor consists of coil and magnet placed on an oil pan with an air gap between the crank shaft timing belt pulley tooth and sensor core.
• Crank shaft sensor allows the system to alter injector opening with respect to changes in engine rpm.
• With respect to the engine speed, the system changes the fuel mixture, where higher speed engines require more fuel and lower speed engines require less fuel.

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