All manufacturers jumped for this fuel injection system mainly to reduce the emissions and to increase the output efficiency of the engine. Every BS-VI emission compliant vehicles use this system in order to meet the emission standards and tuning of the system became somewhat complicated. Before this system became more popular, carburetors were used where we have to just adjust two screws either for getting max mileage or power. But incase of fuel injection system, its all about electronic sensors and actuators. In this article, let's see the overview of this system and about how it works.
Throttle body
The method of sending in the fuel air mixture to the combustion chamber mechanically is known as carburetion and this is done with the help of carburetor. When we twist the throttle, due to the suction created by the piston, air gets sucked into the combustion chamber and the fuel will be sprayed, atomized with the help of nozzle according to the low pressure which is created by the venturi present inside the carburetor body. During the third stroke of the combustion process, spark will be provided with the help of sparkplug, banging and forcing the piston down thereby propelling the vehicle. This is what generally happens in the carburetor.
In case of throttle body, above mentioned nothing will be present. Generally, four things will be present namely Throttle Position Sensor (TPS), Intake Air Temperature sensor (IAT), Manifold Absolute Pressure sensor (MAP) and the fuel injector. All the above mentioned sensors and actuator (fuel injector) will be connected to the brain of the vehicle known as Electronic Control Unit (ECU). In addition to that, oxygen or lambda sensor will be present near the exhaust's header pipe which helps the whole system to work as a closed loop.
Working
When we crank the engine, due to the movement of the piston and opening of the intake valve, air enters the combustion chamber via throttle body. Here comes the action of various sensors which I've mentioned before. Throttle twist grip is directly connected to the butterfly valve present inside the throttle body. It moves according to our input, allowing more air if we twist the throttle more. One side of the butterfly valve is connected to the throttle twist grip with the help of cable or electronically by a servo motor which we call as a Ride by wire system. Other side of the butterfly valve is connected to the Throttle Position Sensor, where it works in a principle of variable resistance. This sensor's output is in the form of voltages, which is directly routed to the ECU.
Intake Air Temperature sensor constantly measures the temperature of the air which is entering the combustion chamber through the throttle body and the Manifold Absolute Pressure sensor monitors the pressure of the intake air constantly where both the sensors sends signal to the ECU all the times. Inside the ECU, there'll be different maps which is programmed already for example ignition map, fuel map etc... Fuel pump in the fuel tank pressurize the fuel and directs it to the fuel injector. What ECU does is, by getting various inputs from the above mentioned sensors, it go through the various maps and activates the fuel injector to atomize & spray the fuel according to it, thereby allowing it to mix with the air flowing to the combustion chamber and bangs inside the combustion chamber during the third stroke of the combustion cycle.
I've mentioned about the closed loop system, remember it? Lambda or oxygen sensor will be present near the exhaust's manifold which constantly monitors the amount of oxygen present at the burnt air fuel mixture coming out from the combustion chamber. It'll pollute our atmosphere if emitted. If oxygen sensor finds more amount of un-burnt oxygen coming out from the combustion chamber, it sends signal to the ECU and varies the parameters according to that to burn the fuel air mixture completely, thereby making more efficient and reducing the emissions.
Surely a question will be raised inside you about the throttle. Air & fuel mixture enters into the engine according to our throttle input. Right??? Then what about the idling condition? What happens in the idling condition? Simple... In the carburetor, the butterfly valve will be closed when we give no input to the throttle. To make the engine idle at the carbureted engines, separate passages will be present to send in the fuel air mixture to the combustion chamber. In the throttle body, there's also a separate passage but it'll be controlled with the help of a valve known as Idle Air Control (IAC) valve. A solenoid will close the passage meant for idling or otherwise known as bypass valve and it'll be controlled by the ECU. When ECU senses that the throttle position is closed with the help of TPS and engine RPM, it activates the solenoid, allowing small amount of air to flow through it and injects the fuel according to the air flow. Thus the engine idles... I've tried to explain the fuel injection system as simple as I could and if you have any suggestion or correction or if I missed out anything, leave it at the comment section below.
Throttle body
The method of sending in the fuel air mixture to the combustion chamber mechanically is known as carburetion and this is done with the help of carburetor. When we twist the throttle, due to the suction created by the piston, air gets sucked into the combustion chamber and the fuel will be sprayed, atomized with the help of nozzle according to the low pressure which is created by the venturi present inside the carburetor body. During the third stroke of the combustion process, spark will be provided with the help of sparkplug, banging and forcing the piston down thereby propelling the vehicle. This is what generally happens in the carburetor.
In case of throttle body, above mentioned nothing will be present. Generally, four things will be present namely Throttle Position Sensor (TPS), Intake Air Temperature sensor (IAT), Manifold Absolute Pressure sensor (MAP) and the fuel injector. All the above mentioned sensors and actuator (fuel injector) will be connected to the brain of the vehicle known as Electronic Control Unit (ECU). In addition to that, oxygen or lambda sensor will be present near the exhaust's header pipe which helps the whole system to work as a closed loop.
Working
When we crank the engine, due to the movement of the piston and opening of the intake valve, air enters the combustion chamber via throttle body. Here comes the action of various sensors which I've mentioned before. Throttle twist grip is directly connected to the butterfly valve present inside the throttle body. It moves according to our input, allowing more air if we twist the throttle more. One side of the butterfly valve is connected to the throttle twist grip with the help of cable or electronically by a servo motor which we call as a Ride by wire system. Other side of the butterfly valve is connected to the Throttle Position Sensor, where it works in a principle of variable resistance. This sensor's output is in the form of voltages, which is directly routed to the ECU.
Intake Air Temperature sensor constantly measures the temperature of the air which is entering the combustion chamber through the throttle body and the Manifold Absolute Pressure sensor monitors the pressure of the intake air constantly where both the sensors sends signal to the ECU all the times. Inside the ECU, there'll be different maps which is programmed already for example ignition map, fuel map etc... Fuel pump in the fuel tank pressurize the fuel and directs it to the fuel injector. What ECU does is, by getting various inputs from the above mentioned sensors, it go through the various maps and activates the fuel injector to atomize & spray the fuel according to it, thereby allowing it to mix with the air flowing to the combustion chamber and bangs inside the combustion chamber during the third stroke of the combustion cycle.
I've mentioned about the closed loop system, remember it? Lambda or oxygen sensor will be present near the exhaust's manifold which constantly monitors the amount of oxygen present at the burnt air fuel mixture coming out from the combustion chamber. It'll pollute our atmosphere if emitted. If oxygen sensor finds more amount of un-burnt oxygen coming out from the combustion chamber, it sends signal to the ECU and varies the parameters according to that to burn the fuel air mixture completely, thereby making more efficient and reducing the emissions.
Surely a question will be raised inside you about the throttle. Air & fuel mixture enters into the engine according to our throttle input. Right??? Then what about the idling condition? What happens in the idling condition? Simple... In the carburetor, the butterfly valve will be closed when we give no input to the throttle. To make the engine idle at the carbureted engines, separate passages will be present to send in the fuel air mixture to the combustion chamber. In the throttle body, there's also a separate passage but it'll be controlled with the help of a valve known as Idle Air Control (IAC) valve. A solenoid will close the passage meant for idling or otherwise known as bypass valve and it'll be controlled by the ECU. When ECU senses that the throttle position is closed with the help of TPS and engine RPM, it activates the solenoid, allowing small amount of air to flow through it and injects the fuel according to the air flow. Thus the engine idles... I've tried to explain the fuel injection system as simple as I could and if you have any suggestion or correction or if I missed out anything, leave it at the comment section below.
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