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Engine Management ECU (EMS ECU)


Engine control unit (ECU) or  Engine control module (ECM), is a type of electronic control unit that ensures optimal engine performance and reduce emission by controlling a number of actuators with the help of data read from a set of sensors aided by software algorithms. In the Pre-ECU Era this mechanisms were controlled by mechanical or pneumatic systems which were often inaccurate and prone to wear and tear.





Engine control units accomplishes various functions but the most important aim is to calculate amount of fuel and​ exact moment of injection​ based on driver demand from the accelerator pedal ,other engine loads and temperature etc... and increase performance , provide good fuel efficiency and reduce emissions . Crank ,camshaft sensors ,pedal position sensors are the primary sensors and injection and ignition valves are the main actuators



If we go into detailed working of EMS,there are 5 major subsystems

  • Injection /ignition System - injectors,ignition coil,speed sensors,etc..
  • Air Intake system - throttle position sensor,turbocharger,etc..
  • Exhaust system - lamda sensor, Selective catalytic reduction, Lean NOx trap, etc...
  • Fuel system - Fuel pump,Fuel tank , fuel pressure sensor,etc..
  • Miscellaneous sensors and loads - Starter motor, Alternator, Heater, AC.etc..

Injection/Ignition System


For gasoline systems the ignition system generates sparks that are necessary for igniting the air-fuel mixture. The optimal ignition timing is calculated by the engine ECU according to each driving condition and it makes the ignition coil to generates high voltage  which is then applied to the spark plug electrodes to generate spark ignition.


Air Intake System


The optimal air/fuel ratio aka the stoichiometric ratio for complete combustion is 14.5:1 air to fuel by volume.(for a Gasoline System, for Diesel system it is 14.7:1). Using Mass airflow sensor the intake system adjusts the air volume needed for combustion using the throttle valve.ECU controls the input from mas airflow sensor and other sensors and controls the throttle






Air pressure can also be controlled by turbocharger by ECUs in Diesel vehicles


Exhaust system


Different Exhaust elements are controlled differently.To control Nitrogen oxides different method are used which include exhaust gas re circulation,NOx storage catalyst and selective catalytic reduction.ECU controls these devices based on the different sensors(NOx sensor or other sensors) to reduce the emission, also injection/ignition and air inflow is also controlled accordingly.Particulate filter is used to reduce particulate matter .Diesel oxidation catalyst is used to reduce hydrocarbons and carbon monoxide


Fuel system



The fuel system controls the fuel supply for the engine. ECU controls the fuel pump and pumps the fuel and maintains pressure at constant required level, and the surplus fuel is returned to the fuel tank. The fuel then travels through the fuel filter where dust and moisture are removed, passes through the delivery pipe, and is fed to the injectors


Miscellaneous


ECU can also control Heater , AC and can support other features like OBDII etc..

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